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23806a3e96
Pull receive_fd update from Al Viro: "Cleanup of receive_fd mess" * 'work.file' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: fs: split receive_fd_replace from __receive_fd
1242 lines
29 KiB
C
1242 lines
29 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/fs/file.c
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*
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* Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
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*
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* Manage the dynamic fd arrays in the process files_struct.
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*/
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#include <linux/syscalls.h>
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#include <linux/export.h>
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#include <linux/fs.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/sched/signal.h>
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#include <linux/slab.h>
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#include <linux/file.h>
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#include <linux/fdtable.h>
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#include <linux/bitops.h>
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#include <linux/spinlock.h>
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#include <linux/rcupdate.h>
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#include <linux/close_range.h>
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#include <net/sock.h>
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#include "internal.h"
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unsigned int sysctl_nr_open __read_mostly = 1024*1024;
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unsigned int sysctl_nr_open_min = BITS_PER_LONG;
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/* our min() is unusable in constant expressions ;-/ */
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#define __const_min(x, y) ((x) < (y) ? (x) : (y))
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unsigned int sysctl_nr_open_max =
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__const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;
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static void __free_fdtable(struct fdtable *fdt)
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{
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kvfree(fdt->fd);
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kvfree(fdt->open_fds);
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kfree(fdt);
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}
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static void free_fdtable_rcu(struct rcu_head *rcu)
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{
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__free_fdtable(container_of(rcu, struct fdtable, rcu));
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}
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#define BITBIT_NR(nr) BITS_TO_LONGS(BITS_TO_LONGS(nr))
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#define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long))
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/*
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* Copy 'count' fd bits from the old table to the new table and clear the extra
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* space if any. This does not copy the file pointers. Called with the files
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* spinlock held for write.
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*/
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static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
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unsigned int count)
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{
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unsigned int cpy, set;
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cpy = count / BITS_PER_BYTE;
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set = (nfdt->max_fds - count) / BITS_PER_BYTE;
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memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
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memset((char *)nfdt->open_fds + cpy, 0, set);
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memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
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memset((char *)nfdt->close_on_exec + cpy, 0, set);
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cpy = BITBIT_SIZE(count);
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set = BITBIT_SIZE(nfdt->max_fds) - cpy;
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memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
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memset((char *)nfdt->full_fds_bits + cpy, 0, set);
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}
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/*
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* Copy all file descriptors from the old table to the new, expanded table and
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* clear the extra space. Called with the files spinlock held for write.
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*/
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static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
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{
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size_t cpy, set;
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BUG_ON(nfdt->max_fds < ofdt->max_fds);
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cpy = ofdt->max_fds * sizeof(struct file *);
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set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
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memcpy(nfdt->fd, ofdt->fd, cpy);
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memset((char *)nfdt->fd + cpy, 0, set);
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copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
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}
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static struct fdtable * alloc_fdtable(unsigned int nr)
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{
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struct fdtable *fdt;
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void *data;
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/*
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* Figure out how many fds we actually want to support in this fdtable.
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* Allocation steps are keyed to the size of the fdarray, since it
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* grows far faster than any of the other dynamic data. We try to fit
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* the fdarray into comfortable page-tuned chunks: starting at 1024B
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* and growing in powers of two from there on.
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*/
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nr /= (1024 / sizeof(struct file *));
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nr = roundup_pow_of_two(nr + 1);
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nr *= (1024 / sizeof(struct file *));
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/*
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* Note that this can drive nr *below* what we had passed if sysctl_nr_open
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* had been set lower between the check in expand_files() and here. Deal
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* with that in caller, it's cheaper that way.
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*
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* We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
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* bitmaps handling below becomes unpleasant, to put it mildly...
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*/
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if (unlikely(nr > sysctl_nr_open))
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nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
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fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
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if (!fdt)
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goto out;
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fdt->max_fds = nr;
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data = kvmalloc_array(nr, sizeof(struct file *), GFP_KERNEL_ACCOUNT);
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if (!data)
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goto out_fdt;
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fdt->fd = data;
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data = kvmalloc(max_t(size_t,
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2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES),
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GFP_KERNEL_ACCOUNT);
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if (!data)
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goto out_arr;
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fdt->open_fds = data;
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data += nr / BITS_PER_BYTE;
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fdt->close_on_exec = data;
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data += nr / BITS_PER_BYTE;
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fdt->full_fds_bits = data;
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return fdt;
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out_arr:
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kvfree(fdt->fd);
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out_fdt:
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kfree(fdt);
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out:
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return NULL;
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}
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/*
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* Expand the file descriptor table.
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* This function will allocate a new fdtable and both fd array and fdset, of
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* the given size.
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* Return <0 error code on error; 1 on successful completion.
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* The files->file_lock should be held on entry, and will be held on exit.
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*/
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static int expand_fdtable(struct files_struct *files, unsigned int nr)
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__releases(files->file_lock)
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__acquires(files->file_lock)
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{
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struct fdtable *new_fdt, *cur_fdt;
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spin_unlock(&files->file_lock);
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new_fdt = alloc_fdtable(nr);
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/* make sure all fd_install() have seen resize_in_progress
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* or have finished their rcu_read_lock_sched() section.
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*/
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if (atomic_read(&files->count) > 1)
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synchronize_rcu();
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spin_lock(&files->file_lock);
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if (!new_fdt)
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return -ENOMEM;
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/*
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* extremely unlikely race - sysctl_nr_open decreased between the check in
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* caller and alloc_fdtable(). Cheaper to catch it here...
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*/
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if (unlikely(new_fdt->max_fds <= nr)) {
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__free_fdtable(new_fdt);
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return -EMFILE;
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}
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cur_fdt = files_fdtable(files);
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BUG_ON(nr < cur_fdt->max_fds);
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copy_fdtable(new_fdt, cur_fdt);
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rcu_assign_pointer(files->fdt, new_fdt);
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if (cur_fdt != &files->fdtab)
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call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
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/* coupled with smp_rmb() in fd_install() */
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smp_wmb();
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return 1;
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}
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/*
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* Expand files.
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* This function will expand the file structures, if the requested size exceeds
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* the current capacity and there is room for expansion.
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* Return <0 error code on error; 0 when nothing done; 1 when files were
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* expanded and execution may have blocked.
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* The files->file_lock should be held on entry, and will be held on exit.
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*/
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static int expand_files(struct files_struct *files, unsigned int nr)
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__releases(files->file_lock)
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__acquires(files->file_lock)
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{
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struct fdtable *fdt;
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int expanded = 0;
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repeat:
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fdt = files_fdtable(files);
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/* Do we need to expand? */
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if (nr < fdt->max_fds)
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return expanded;
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/* Can we expand? */
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if (nr >= sysctl_nr_open)
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return -EMFILE;
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if (unlikely(files->resize_in_progress)) {
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spin_unlock(&files->file_lock);
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expanded = 1;
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wait_event(files->resize_wait, !files->resize_in_progress);
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spin_lock(&files->file_lock);
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goto repeat;
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}
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/* All good, so we try */
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files->resize_in_progress = true;
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expanded = expand_fdtable(files, nr);
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files->resize_in_progress = false;
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wake_up_all(&files->resize_wait);
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return expanded;
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}
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static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt)
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{
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__set_bit(fd, fdt->close_on_exec);
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}
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static inline void __clear_close_on_exec(unsigned int fd, struct fdtable *fdt)
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{
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if (test_bit(fd, fdt->close_on_exec))
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__clear_bit(fd, fdt->close_on_exec);
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}
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static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
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{
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__set_bit(fd, fdt->open_fds);
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fd /= BITS_PER_LONG;
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if (!~fdt->open_fds[fd])
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__set_bit(fd, fdt->full_fds_bits);
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}
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static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
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{
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__clear_bit(fd, fdt->open_fds);
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__clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
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}
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static unsigned int count_open_files(struct fdtable *fdt)
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{
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unsigned int size = fdt->max_fds;
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unsigned int i;
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/* Find the last open fd */
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for (i = size / BITS_PER_LONG; i > 0; ) {
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if (fdt->open_fds[--i])
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break;
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}
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i = (i + 1) * BITS_PER_LONG;
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return i;
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}
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static unsigned int sane_fdtable_size(struct fdtable *fdt, unsigned int max_fds)
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{
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unsigned int count;
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count = count_open_files(fdt);
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if (max_fds < NR_OPEN_DEFAULT)
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max_fds = NR_OPEN_DEFAULT;
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return min(count, max_fds);
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}
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/*
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* Allocate a new files structure and copy contents from the
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* passed in files structure.
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* errorp will be valid only when the returned files_struct is NULL.
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*/
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struct files_struct *dup_fd(struct files_struct *oldf, unsigned int max_fds, int *errorp)
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{
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struct files_struct *newf;
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struct file **old_fds, **new_fds;
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unsigned int open_files, i;
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struct fdtable *old_fdt, *new_fdt;
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*errorp = -ENOMEM;
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newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
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if (!newf)
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goto out;
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atomic_set(&newf->count, 1);
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spin_lock_init(&newf->file_lock);
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newf->resize_in_progress = false;
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init_waitqueue_head(&newf->resize_wait);
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newf->next_fd = 0;
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new_fdt = &newf->fdtab;
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new_fdt->max_fds = NR_OPEN_DEFAULT;
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new_fdt->close_on_exec = newf->close_on_exec_init;
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new_fdt->open_fds = newf->open_fds_init;
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new_fdt->full_fds_bits = newf->full_fds_bits_init;
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new_fdt->fd = &newf->fd_array[0];
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spin_lock(&oldf->file_lock);
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old_fdt = files_fdtable(oldf);
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open_files = sane_fdtable_size(old_fdt, max_fds);
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/*
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* Check whether we need to allocate a larger fd array and fd set.
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*/
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while (unlikely(open_files > new_fdt->max_fds)) {
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spin_unlock(&oldf->file_lock);
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if (new_fdt != &newf->fdtab)
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__free_fdtable(new_fdt);
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new_fdt = alloc_fdtable(open_files - 1);
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if (!new_fdt) {
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*errorp = -ENOMEM;
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goto out_release;
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}
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/* beyond sysctl_nr_open; nothing to do */
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if (unlikely(new_fdt->max_fds < open_files)) {
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__free_fdtable(new_fdt);
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*errorp = -EMFILE;
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goto out_release;
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}
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/*
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* Reacquire the oldf lock and a pointer to its fd table
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* who knows it may have a new bigger fd table. We need
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* the latest pointer.
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*/
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spin_lock(&oldf->file_lock);
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old_fdt = files_fdtable(oldf);
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open_files = sane_fdtable_size(old_fdt, max_fds);
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}
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copy_fd_bitmaps(new_fdt, old_fdt, open_files);
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old_fds = old_fdt->fd;
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new_fds = new_fdt->fd;
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for (i = open_files; i != 0; i--) {
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struct file *f = *old_fds++;
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if (f) {
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get_file(f);
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} else {
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/*
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* The fd may be claimed in the fd bitmap but not yet
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* instantiated in the files array if a sibling thread
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* is partway through open(). So make sure that this
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* fd is available to the new process.
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*/
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__clear_open_fd(open_files - i, new_fdt);
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}
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rcu_assign_pointer(*new_fds++, f);
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}
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spin_unlock(&oldf->file_lock);
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/* clear the remainder */
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memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *));
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rcu_assign_pointer(newf->fdt, new_fdt);
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return newf;
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out_release:
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kmem_cache_free(files_cachep, newf);
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out:
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return NULL;
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}
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static struct fdtable *close_files(struct files_struct * files)
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{
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/*
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* It is safe to dereference the fd table without RCU or
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* ->file_lock because this is the last reference to the
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* files structure.
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*/
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struct fdtable *fdt = rcu_dereference_raw(files->fdt);
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unsigned int i, j = 0;
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for (;;) {
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unsigned long set;
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i = j * BITS_PER_LONG;
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if (i >= fdt->max_fds)
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break;
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set = fdt->open_fds[j++];
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while (set) {
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if (set & 1) {
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struct file * file = xchg(&fdt->fd[i], NULL);
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if (file) {
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filp_close(file, files);
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cond_resched();
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}
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}
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i++;
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set >>= 1;
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}
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}
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return fdt;
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}
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void put_files_struct(struct files_struct *files)
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{
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if (atomic_dec_and_test(&files->count)) {
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struct fdtable *fdt = close_files(files);
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|
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/* free the arrays if they are not embedded */
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if (fdt != &files->fdtab)
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__free_fdtable(fdt);
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kmem_cache_free(files_cachep, files);
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}
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}
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void exit_files(struct task_struct *tsk)
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{
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struct files_struct * files = tsk->files;
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|
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if (files) {
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task_lock(tsk);
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tsk->files = NULL;
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task_unlock(tsk);
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put_files_struct(files);
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}
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}
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|
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struct files_struct init_files = {
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.count = ATOMIC_INIT(1),
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.fdt = &init_files.fdtab,
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.fdtab = {
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.max_fds = NR_OPEN_DEFAULT,
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.fd = &init_files.fd_array[0],
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.close_on_exec = init_files.close_on_exec_init,
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.open_fds = init_files.open_fds_init,
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.full_fds_bits = init_files.full_fds_bits_init,
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},
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.file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock),
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.resize_wait = __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait),
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};
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|
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static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
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{
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unsigned int maxfd = fdt->max_fds;
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unsigned int maxbit = maxfd / BITS_PER_LONG;
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unsigned int bitbit = start / BITS_PER_LONG;
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|
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bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
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if (bitbit > maxfd)
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return maxfd;
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if (bitbit > start)
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start = bitbit;
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return find_next_zero_bit(fdt->open_fds, maxfd, start);
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}
|
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|
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/*
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* allocate a file descriptor, mark it busy.
|
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*/
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static int alloc_fd(unsigned start, unsigned end, unsigned flags)
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{
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struct files_struct *files = current->files;
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unsigned int fd;
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int error;
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struct fdtable *fdt;
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|
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spin_lock(&files->file_lock);
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|
repeat:
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|
fdt = files_fdtable(files);
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fd = start;
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if (fd < files->next_fd)
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fd = files->next_fd;
|
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|
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if (fd < fdt->max_fds)
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fd = find_next_fd(fdt, fd);
|
|
|
|
/*
|
|
* N.B. For clone tasks sharing a files structure, this test
|
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* will limit the total number of files that can be opened.
|
|
*/
|
|
error = -EMFILE;
|
|
if (fd >= end)
|
|
goto out;
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|
|
|
error = expand_files(files, fd);
|
|
if (error < 0)
|
|
goto out;
|
|
|
|
/*
|
|
* If we needed to expand the fs array we
|
|
* might have blocked - try again.
|
|
*/
|
|
if (error)
|
|
goto repeat;
|
|
|
|
if (start <= files->next_fd)
|
|
files->next_fd = fd + 1;
|
|
|
|
__set_open_fd(fd, fdt);
|
|
if (flags & O_CLOEXEC)
|
|
__set_close_on_exec(fd, fdt);
|
|
else
|
|
__clear_close_on_exec(fd, fdt);
|
|
error = fd;
|
|
#if 1
|
|
/* Sanity check */
|
|
if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
|
|
printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
|
|
rcu_assign_pointer(fdt->fd[fd], NULL);
|
|
}
|
|
#endif
|
|
|
|
out:
|
|
spin_unlock(&files->file_lock);
|
|
return error;
|
|
}
|
|
|
|
int __get_unused_fd_flags(unsigned flags, unsigned long nofile)
|
|
{
|
|
return alloc_fd(0, nofile, flags);
|
|
}
|
|
|
|
int get_unused_fd_flags(unsigned flags)
|
|
{
|
|
return __get_unused_fd_flags(flags, rlimit(RLIMIT_NOFILE));
|
|
}
|
|
EXPORT_SYMBOL(get_unused_fd_flags);
|
|
|
|
static void __put_unused_fd(struct files_struct *files, unsigned int fd)
|
|
{
|
|
struct fdtable *fdt = files_fdtable(files);
|
|
__clear_open_fd(fd, fdt);
|
|
if (fd < files->next_fd)
|
|
files->next_fd = fd;
|
|
}
|
|
|
|
void put_unused_fd(unsigned int fd)
|
|
{
|
|
struct files_struct *files = current->files;
|
|
spin_lock(&files->file_lock);
|
|
__put_unused_fd(files, fd);
|
|
spin_unlock(&files->file_lock);
|
|
}
|
|
|
|
EXPORT_SYMBOL(put_unused_fd);
|
|
|
|
/*
|
|
* Install a file pointer in the fd array.
|
|
*
|
|
* The VFS is full of places where we drop the files lock between
|
|
* setting the open_fds bitmap and installing the file in the file
|
|
* array. At any such point, we are vulnerable to a dup2() race
|
|
* installing a file in the array before us. We need to detect this and
|
|
* fput() the struct file we are about to overwrite in this case.
|
|
*
|
|
* It should never happen - if we allow dup2() do it, _really_ bad things
|
|
* will follow.
|
|
*
|
|
* This consumes the "file" refcount, so callers should treat it
|
|
* as if they had called fput(file).
|
|
*/
|
|
|
|
void fd_install(unsigned int fd, struct file *file)
|
|
{
|
|
struct files_struct *files = current->files;
|
|
struct fdtable *fdt;
|
|
|
|
rcu_read_lock_sched();
|
|
|
|
if (unlikely(files->resize_in_progress)) {
|
|
rcu_read_unlock_sched();
|
|
spin_lock(&files->file_lock);
|
|
fdt = files_fdtable(files);
|
|
BUG_ON(fdt->fd[fd] != NULL);
|
|
rcu_assign_pointer(fdt->fd[fd], file);
|
|
spin_unlock(&files->file_lock);
|
|
return;
|
|
}
|
|
/* coupled with smp_wmb() in expand_fdtable() */
|
|
smp_rmb();
|
|
fdt = rcu_dereference_sched(files->fdt);
|
|
BUG_ON(fdt->fd[fd] != NULL);
|
|
rcu_assign_pointer(fdt->fd[fd], file);
|
|
rcu_read_unlock_sched();
|
|
}
|
|
|
|
EXPORT_SYMBOL(fd_install);
|
|
|
|
static struct file *pick_file(struct files_struct *files, unsigned fd)
|
|
{
|
|
struct file *file = NULL;
|
|
struct fdtable *fdt;
|
|
|
|
spin_lock(&files->file_lock);
|
|
fdt = files_fdtable(files);
|
|
if (fd >= fdt->max_fds)
|
|
goto out_unlock;
|
|
file = fdt->fd[fd];
|
|
if (!file)
|
|
goto out_unlock;
|
|
rcu_assign_pointer(fdt->fd[fd], NULL);
|
|
__put_unused_fd(files, fd);
|
|
|
|
out_unlock:
|
|
spin_unlock(&files->file_lock);
|
|
return file;
|
|
}
|
|
|
|
int close_fd(unsigned fd)
|
|
{
|
|
struct files_struct *files = current->files;
|
|
struct file *file;
|
|
|
|
file = pick_file(files, fd);
|
|
if (!file)
|
|
return -EBADF;
|
|
|
|
return filp_close(file, files);
|
|
}
|
|
EXPORT_SYMBOL(close_fd); /* for ksys_close() */
|
|
|
|
/**
|
|
* last_fd - return last valid index into fd table
|
|
* @cur_fds: files struct
|
|
*
|
|
* Context: Either rcu read lock or files_lock must be held.
|
|
*
|
|
* Returns: Last valid index into fdtable.
|
|
*/
|
|
static inline unsigned last_fd(struct fdtable *fdt)
|
|
{
|
|
return fdt->max_fds - 1;
|
|
}
|
|
|
|
static inline void __range_cloexec(struct files_struct *cur_fds,
|
|
unsigned int fd, unsigned int max_fd)
|
|
{
|
|
struct fdtable *fdt;
|
|
|
|
/* make sure we're using the correct maximum value */
|
|
spin_lock(&cur_fds->file_lock);
|
|
fdt = files_fdtable(cur_fds);
|
|
max_fd = min(last_fd(fdt), max_fd);
|
|
if (fd <= max_fd)
|
|
bitmap_set(fdt->close_on_exec, fd, max_fd - fd + 1);
|
|
spin_unlock(&cur_fds->file_lock);
|
|
}
|
|
|
|
static inline void __range_close(struct files_struct *cur_fds, unsigned int fd,
|
|
unsigned int max_fd)
|
|
{
|
|
while (fd <= max_fd) {
|
|
struct file *file;
|
|
|
|
file = pick_file(cur_fds, fd++);
|
|
if (!file)
|
|
continue;
|
|
|
|
filp_close(file, cur_fds);
|
|
cond_resched();
|
|
}
|
|
}
|
|
|
|
/**
|
|
* __close_range() - Close all file descriptors in a given range.
|
|
*
|
|
* @fd: starting file descriptor to close
|
|
* @max_fd: last file descriptor to close
|
|
*
|
|
* This closes a range of file descriptors. All file descriptors
|
|
* from @fd up to and including @max_fd are closed.
|
|
*/
|
|
int __close_range(unsigned fd, unsigned max_fd, unsigned int flags)
|
|
{
|
|
unsigned int cur_max;
|
|
struct task_struct *me = current;
|
|
struct files_struct *cur_fds = me->files, *fds = NULL;
|
|
|
|
if (flags & ~(CLOSE_RANGE_UNSHARE | CLOSE_RANGE_CLOEXEC))
|
|
return -EINVAL;
|
|
|
|
if (fd > max_fd)
|
|
return -EINVAL;
|
|
|
|
rcu_read_lock();
|
|
cur_max = files_fdtable(cur_fds)->max_fds;
|
|
rcu_read_unlock();
|
|
|
|
/* cap to last valid index into fdtable */
|
|
cur_max--;
|
|
|
|
if (flags & CLOSE_RANGE_UNSHARE) {
|
|
int ret;
|
|
unsigned int max_unshare_fds = NR_OPEN_MAX;
|
|
|
|
/*
|
|
* If the requested range is greater than the current maximum,
|
|
* we're closing everything so only copy all file descriptors
|
|
* beneath the lowest file descriptor.
|
|
* If the caller requested all fds to be made cloexec copy all
|
|
* of the file descriptors since they still want to use them.
|
|
*/
|
|
if (!(flags & CLOSE_RANGE_CLOEXEC) && (max_fd >= cur_max))
|
|
max_unshare_fds = fd;
|
|
|
|
ret = unshare_fd(CLONE_FILES, max_unshare_fds, &fds);
|
|
if (ret)
|
|
return ret;
|
|
|
|
/*
|
|
* We used to share our file descriptor table, and have now
|
|
* created a private one, make sure we're using it below.
|
|
*/
|
|
if (fds)
|
|
swap(cur_fds, fds);
|
|
}
|
|
|
|
max_fd = min(max_fd, cur_max);
|
|
|
|
if (flags & CLOSE_RANGE_CLOEXEC)
|
|
__range_cloexec(cur_fds, fd, max_fd);
|
|
else
|
|
__range_close(cur_fds, fd, max_fd);
|
|
|
|
if (fds) {
|
|
/*
|
|
* We're done closing the files we were supposed to. Time to install
|
|
* the new file descriptor table and drop the old one.
|
|
*/
|
|
task_lock(me);
|
|
me->files = cur_fds;
|
|
task_unlock(me);
|
|
put_files_struct(fds);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* See close_fd_get_file() below, this variant assumes current->files->file_lock
|
|
* is held.
|
|
*/
|
|
int __close_fd_get_file(unsigned int fd, struct file **res)
|
|
{
|
|
struct files_struct *files = current->files;
|
|
struct file *file;
|
|
struct fdtable *fdt;
|
|
|
|
fdt = files_fdtable(files);
|
|
if (fd >= fdt->max_fds)
|
|
goto out_err;
|
|
file = fdt->fd[fd];
|
|
if (!file)
|
|
goto out_err;
|
|
rcu_assign_pointer(fdt->fd[fd], NULL);
|
|
__put_unused_fd(files, fd);
|
|
get_file(file);
|
|
*res = file;
|
|
return 0;
|
|
out_err:
|
|
*res = NULL;
|
|
return -ENOENT;
|
|
}
|
|
|
|
/*
|
|
* variant of close_fd that gets a ref on the file for later fput.
|
|
* The caller must ensure that filp_close() called on the file, and then
|
|
* an fput().
|
|
*/
|
|
int close_fd_get_file(unsigned int fd, struct file **res)
|
|
{
|
|
struct files_struct *files = current->files;
|
|
int ret;
|
|
|
|
spin_lock(&files->file_lock);
|
|
ret = __close_fd_get_file(fd, res);
|
|
spin_unlock(&files->file_lock);
|
|
|
|
return ret;
|
|
}
|
|
|
|
void do_close_on_exec(struct files_struct *files)
|
|
{
|
|
unsigned i;
|
|
struct fdtable *fdt;
|
|
|
|
/* exec unshares first */
|
|
spin_lock(&files->file_lock);
|
|
for (i = 0; ; i++) {
|
|
unsigned long set;
|
|
unsigned fd = i * BITS_PER_LONG;
|
|
fdt = files_fdtable(files);
|
|
if (fd >= fdt->max_fds)
|
|
break;
|
|
set = fdt->close_on_exec[i];
|
|
if (!set)
|
|
continue;
|
|
fdt->close_on_exec[i] = 0;
|
|
for ( ; set ; fd++, set >>= 1) {
|
|
struct file *file;
|
|
if (!(set & 1))
|
|
continue;
|
|
file = fdt->fd[fd];
|
|
if (!file)
|
|
continue;
|
|
rcu_assign_pointer(fdt->fd[fd], NULL);
|
|
__put_unused_fd(files, fd);
|
|
spin_unlock(&files->file_lock);
|
|
filp_close(file, files);
|
|
cond_resched();
|
|
spin_lock(&files->file_lock);
|
|
}
|
|
|
|
}
|
|
spin_unlock(&files->file_lock);
|
|
}
|
|
|
|
static struct file *__fget_files(struct files_struct *files, unsigned int fd,
|
|
fmode_t mask, unsigned int refs)
|
|
{
|
|
struct file *file;
|
|
|
|
rcu_read_lock();
|
|
loop:
|
|
file = files_lookup_fd_rcu(files, fd);
|
|
if (file) {
|
|
/* File object ref couldn't be taken.
|
|
* dup2() atomicity guarantee is the reason
|
|
* we loop to catch the new file (or NULL pointer)
|
|
*/
|
|
if (file->f_mode & mask)
|
|
file = NULL;
|
|
else if (!get_file_rcu_many(file, refs))
|
|
goto loop;
|
|
}
|
|
rcu_read_unlock();
|
|
|
|
return file;
|
|
}
|
|
|
|
static inline struct file *__fget(unsigned int fd, fmode_t mask,
|
|
unsigned int refs)
|
|
{
|
|
return __fget_files(current->files, fd, mask, refs);
|
|
}
|
|
|
|
struct file *fget_many(unsigned int fd, unsigned int refs)
|
|
{
|
|
return __fget(fd, FMODE_PATH, refs);
|
|
}
|
|
|
|
struct file *fget(unsigned int fd)
|
|
{
|
|
return __fget(fd, FMODE_PATH, 1);
|
|
}
|
|
EXPORT_SYMBOL(fget);
|
|
|
|
struct file *fget_raw(unsigned int fd)
|
|
{
|
|
return __fget(fd, 0, 1);
|
|
}
|
|
EXPORT_SYMBOL(fget_raw);
|
|
|
|
struct file *fget_task(struct task_struct *task, unsigned int fd)
|
|
{
|
|
struct file *file = NULL;
|
|
|
|
task_lock(task);
|
|
if (task->files)
|
|
file = __fget_files(task->files, fd, 0, 1);
|
|
task_unlock(task);
|
|
|
|
return file;
|
|
}
|
|
|
|
struct file *task_lookup_fd_rcu(struct task_struct *task, unsigned int fd)
|
|
{
|
|
/* Must be called with rcu_read_lock held */
|
|
struct files_struct *files;
|
|
struct file *file = NULL;
|
|
|
|
task_lock(task);
|
|
files = task->files;
|
|
if (files)
|
|
file = files_lookup_fd_rcu(files, fd);
|
|
task_unlock(task);
|
|
|
|
return file;
|
|
}
|
|
|
|
struct file *task_lookup_next_fd_rcu(struct task_struct *task, unsigned int *ret_fd)
|
|
{
|
|
/* Must be called with rcu_read_lock held */
|
|
struct files_struct *files;
|
|
unsigned int fd = *ret_fd;
|
|
struct file *file = NULL;
|
|
|
|
task_lock(task);
|
|
files = task->files;
|
|
if (files) {
|
|
for (; fd < files_fdtable(files)->max_fds; fd++) {
|
|
file = files_lookup_fd_rcu(files, fd);
|
|
if (file)
|
|
break;
|
|
}
|
|
}
|
|
task_unlock(task);
|
|
*ret_fd = fd;
|
|
return file;
|
|
}
|
|
|
|
/*
|
|
* Lightweight file lookup - no refcnt increment if fd table isn't shared.
|
|
*
|
|
* You can use this instead of fget if you satisfy all of the following
|
|
* conditions:
|
|
* 1) You must call fput_light before exiting the syscall and returning control
|
|
* to userspace (i.e. you cannot remember the returned struct file * after
|
|
* returning to userspace).
|
|
* 2) You must not call filp_close on the returned struct file * in between
|
|
* calls to fget_light and fput_light.
|
|
* 3) You must not clone the current task in between the calls to fget_light
|
|
* and fput_light.
|
|
*
|
|
* The fput_needed flag returned by fget_light should be passed to the
|
|
* corresponding fput_light.
|
|
*/
|
|
static unsigned long __fget_light(unsigned int fd, fmode_t mask)
|
|
{
|
|
struct files_struct *files = current->files;
|
|
struct file *file;
|
|
|
|
if (atomic_read(&files->count) == 1) {
|
|
file = files_lookup_fd_raw(files, fd);
|
|
if (!file || unlikely(file->f_mode & mask))
|
|
return 0;
|
|
return (unsigned long)file;
|
|
} else {
|
|
file = __fget(fd, mask, 1);
|
|
if (!file)
|
|
return 0;
|
|
return FDPUT_FPUT | (unsigned long)file;
|
|
}
|
|
}
|
|
unsigned long __fdget(unsigned int fd)
|
|
{
|
|
return __fget_light(fd, FMODE_PATH);
|
|
}
|
|
EXPORT_SYMBOL(__fdget);
|
|
|
|
unsigned long __fdget_raw(unsigned int fd)
|
|
{
|
|
return __fget_light(fd, 0);
|
|
}
|
|
|
|
unsigned long __fdget_pos(unsigned int fd)
|
|
{
|
|
unsigned long v = __fdget(fd);
|
|
struct file *file = (struct file *)(v & ~3);
|
|
|
|
if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
|
|
if (file_count(file) > 1) {
|
|
v |= FDPUT_POS_UNLOCK;
|
|
mutex_lock(&file->f_pos_lock);
|
|
}
|
|
}
|
|
return v;
|
|
}
|
|
|
|
void __f_unlock_pos(struct file *f)
|
|
{
|
|
mutex_unlock(&f->f_pos_lock);
|
|
}
|
|
|
|
/*
|
|
* We only lock f_pos if we have threads or if the file might be
|
|
* shared with another process. In both cases we'll have an elevated
|
|
* file count (done either by fdget() or by fork()).
|
|
*/
|
|
|
|
void set_close_on_exec(unsigned int fd, int flag)
|
|
{
|
|
struct files_struct *files = current->files;
|
|
struct fdtable *fdt;
|
|
spin_lock(&files->file_lock);
|
|
fdt = files_fdtable(files);
|
|
if (flag)
|
|
__set_close_on_exec(fd, fdt);
|
|
else
|
|
__clear_close_on_exec(fd, fdt);
|
|
spin_unlock(&files->file_lock);
|
|
}
|
|
|
|
bool get_close_on_exec(unsigned int fd)
|
|
{
|
|
struct files_struct *files = current->files;
|
|
struct fdtable *fdt;
|
|
bool res;
|
|
rcu_read_lock();
|
|
fdt = files_fdtable(files);
|
|
res = close_on_exec(fd, fdt);
|
|
rcu_read_unlock();
|
|
return res;
|
|
}
|
|
|
|
static int do_dup2(struct files_struct *files,
|
|
struct file *file, unsigned fd, unsigned flags)
|
|
__releases(&files->file_lock)
|
|
{
|
|
struct file *tofree;
|
|
struct fdtable *fdt;
|
|
|
|
/*
|
|
* We need to detect attempts to do dup2() over allocated but still
|
|
* not finished descriptor. NB: OpenBSD avoids that at the price of
|
|
* extra work in their equivalent of fget() - they insert struct
|
|
* file immediately after grabbing descriptor, mark it larval if
|
|
* more work (e.g. actual opening) is needed and make sure that
|
|
* fget() treats larval files as absent. Potentially interesting,
|
|
* but while extra work in fget() is trivial, locking implications
|
|
* and amount of surgery on open()-related paths in VFS are not.
|
|
* FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
|
|
* deadlocks in rather amusing ways, AFAICS. All of that is out of
|
|
* scope of POSIX or SUS, since neither considers shared descriptor
|
|
* tables and this condition does not arise without those.
|
|
*/
|
|
fdt = files_fdtable(files);
|
|
tofree = fdt->fd[fd];
|
|
if (!tofree && fd_is_open(fd, fdt))
|
|
goto Ebusy;
|
|
get_file(file);
|
|
rcu_assign_pointer(fdt->fd[fd], file);
|
|
__set_open_fd(fd, fdt);
|
|
if (flags & O_CLOEXEC)
|
|
__set_close_on_exec(fd, fdt);
|
|
else
|
|
__clear_close_on_exec(fd, fdt);
|
|
spin_unlock(&files->file_lock);
|
|
|
|
if (tofree)
|
|
filp_close(tofree, files);
|
|
|
|
return fd;
|
|
|
|
Ebusy:
|
|
spin_unlock(&files->file_lock);
|
|
return -EBUSY;
|
|
}
|
|
|
|
int replace_fd(unsigned fd, struct file *file, unsigned flags)
|
|
{
|
|
int err;
|
|
struct files_struct *files = current->files;
|
|
|
|
if (!file)
|
|
return close_fd(fd);
|
|
|
|
if (fd >= rlimit(RLIMIT_NOFILE))
|
|
return -EBADF;
|
|
|
|
spin_lock(&files->file_lock);
|
|
err = expand_files(files, fd);
|
|
if (unlikely(err < 0))
|
|
goto out_unlock;
|
|
return do_dup2(files, file, fd, flags);
|
|
|
|
out_unlock:
|
|
spin_unlock(&files->file_lock);
|
|
return err;
|
|
}
|
|
|
|
/**
|
|
* __receive_fd() - Install received file into file descriptor table
|
|
* @file: struct file that was received from another process
|
|
* @ufd: __user pointer to write new fd number to
|
|
* @o_flags: the O_* flags to apply to the new fd entry
|
|
*
|
|
* Installs a received file into the file descriptor table, with appropriate
|
|
* checks and count updates. Optionally writes the fd number to userspace, if
|
|
* @ufd is non-NULL.
|
|
*
|
|
* This helper handles its own reference counting of the incoming
|
|
* struct file.
|
|
*
|
|
* Returns newly install fd or -ve on error.
|
|
*/
|
|
int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags)
|
|
{
|
|
int new_fd;
|
|
int error;
|
|
|
|
error = security_file_receive(file);
|
|
if (error)
|
|
return error;
|
|
|
|
new_fd = get_unused_fd_flags(o_flags);
|
|
if (new_fd < 0)
|
|
return new_fd;
|
|
|
|
if (ufd) {
|
|
error = put_user(new_fd, ufd);
|
|
if (error) {
|
|
put_unused_fd(new_fd);
|
|
return error;
|
|
}
|
|
}
|
|
|
|
fd_install(new_fd, get_file(file));
|
|
__receive_sock(file);
|
|
return new_fd;
|
|
}
|
|
|
|
int receive_fd_replace(int new_fd, struct file *file, unsigned int o_flags)
|
|
{
|
|
int error;
|
|
|
|
error = security_file_receive(file);
|
|
if (error)
|
|
return error;
|
|
error = replace_fd(new_fd, file, o_flags);
|
|
if (error)
|
|
return error;
|
|
__receive_sock(file);
|
|
return new_fd;
|
|
}
|
|
|
|
static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
|
|
{
|
|
int err = -EBADF;
|
|
struct file *file;
|
|
struct files_struct *files = current->files;
|
|
|
|
if ((flags & ~O_CLOEXEC) != 0)
|
|
return -EINVAL;
|
|
|
|
if (unlikely(oldfd == newfd))
|
|
return -EINVAL;
|
|
|
|
if (newfd >= rlimit(RLIMIT_NOFILE))
|
|
return -EBADF;
|
|
|
|
spin_lock(&files->file_lock);
|
|
err = expand_files(files, newfd);
|
|
file = files_lookup_fd_locked(files, oldfd);
|
|
if (unlikely(!file))
|
|
goto Ebadf;
|
|
if (unlikely(err < 0)) {
|
|
if (err == -EMFILE)
|
|
goto Ebadf;
|
|
goto out_unlock;
|
|
}
|
|
return do_dup2(files, file, newfd, flags);
|
|
|
|
Ebadf:
|
|
err = -EBADF;
|
|
out_unlock:
|
|
spin_unlock(&files->file_lock);
|
|
return err;
|
|
}
|
|
|
|
SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
|
|
{
|
|
return ksys_dup3(oldfd, newfd, flags);
|
|
}
|
|
|
|
SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
|
|
{
|
|
if (unlikely(newfd == oldfd)) { /* corner case */
|
|
struct files_struct *files = current->files;
|
|
int retval = oldfd;
|
|
|
|
rcu_read_lock();
|
|
if (!files_lookup_fd_rcu(files, oldfd))
|
|
retval = -EBADF;
|
|
rcu_read_unlock();
|
|
return retval;
|
|
}
|
|
return ksys_dup3(oldfd, newfd, 0);
|
|
}
|
|
|
|
SYSCALL_DEFINE1(dup, unsigned int, fildes)
|
|
{
|
|
int ret = -EBADF;
|
|
struct file *file = fget_raw(fildes);
|
|
|
|
if (file) {
|
|
ret = get_unused_fd_flags(0);
|
|
if (ret >= 0)
|
|
fd_install(ret, file);
|
|
else
|
|
fput(file);
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
int f_dupfd(unsigned int from, struct file *file, unsigned flags)
|
|
{
|
|
unsigned long nofile = rlimit(RLIMIT_NOFILE);
|
|
int err;
|
|
if (from >= nofile)
|
|
return -EINVAL;
|
|
err = alloc_fd(from, nofile, flags);
|
|
if (err >= 0) {
|
|
get_file(file);
|
|
fd_install(err, file);
|
|
}
|
|
return err;
|
|
}
|
|
|
|
int iterate_fd(struct files_struct *files, unsigned n,
|
|
int (*f)(const void *, struct file *, unsigned),
|
|
const void *p)
|
|
{
|
|
struct fdtable *fdt;
|
|
int res = 0;
|
|
if (!files)
|
|
return 0;
|
|
spin_lock(&files->file_lock);
|
|
for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
|
|
struct file *file;
|
|
file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
|
|
if (!file)
|
|
continue;
|
|
res = f(p, file, n);
|
|
if (res)
|
|
break;
|
|
}
|
|
spin_unlock(&files->file_lock);
|
|
return res;
|
|
}
|
|
EXPORT_SYMBOL(iterate_fd);
|