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linux-next/include/linux/kernfs.h
Tejun Heo b7ce40cff0 kernfs: cache atomic_write_len in kernfs_open_file
While implementing atomic_write_len, 4d3773c4bb ("kernfs: implement
kernfs_ops->atomic_write_len") moved data copy from userland inside
kernfs_get_active() and kernfs_open_file->mutex so that
kernfs_ops->atomic_write_len can be accessed before copying buffer
from userland; unfortunately, this could lead to locking order
inversion involving mmap_sem if copy_from_user() takes a page fault.

  ======================================================
  [ INFO: possible circular locking dependency detected ]
  3.14.0-rc4-next-20140228-sasha-00011-g4077c67-dirty #26 Tainted: G        W
  -------------------------------------------------------
  trinity-c236/10658 is trying to acquire lock:
   (&of->mutex#2){+.+.+.}, at: [<fs/kernfs/file.c:487>] kernfs_fop_mmap+0x54/0x120

  but task is already holding lock:
   (&mm->mmap_sem){++++++}, at: [<mm/util.c:397>] vm_mmap_pgoff+0x6e/0xe0

  which lock already depends on the new lock.

  the existing dependency chain (in reverse order) is:

 -> #1 (&mm->mmap_sem){++++++}:
	 [<kernel/locking/lockdep.c:1945 kernel/locking/lockdep.c:2131>] validate_chain+0x6c5/0x7b0
	 [<kernel/locking/lockdep.c:3182>] __lock_acquire+0x4cd/0x5a0
	 [<arch/x86/include/asm/current.h:14 kernel/locking/lockdep.c:3602>] lock_acquire+0x182/0x1d0
	 [<mm/memory.c:4188>] might_fault+0x7e/0xb0
	 [<arch/x86/include/asm/uaccess.h:713 fs/kernfs/file.c:291>] kernfs_fop_write+0xd8/0x190
	 [<fs/read_write.c:473>] vfs_write+0xe3/0x1d0
	 [<fs/read_write.c:523 fs/read_write.c:515>] SyS_write+0x5d/0xa0
	 [<arch/x86/kernel/entry_64.S:749>] tracesys+0xdd/0xe2

 -> #0 (&of->mutex#2){+.+.+.}:
	 [<kernel/locking/lockdep.c:1840>] check_prev_add+0x13f/0x560
	 [<kernel/locking/lockdep.c:1945 kernel/locking/lockdep.c:2131>] validate_chain+0x6c5/0x7b0
	 [<kernel/locking/lockdep.c:3182>] __lock_acquire+0x4cd/0x5a0
	 [<arch/x86/include/asm/current.h:14 kernel/locking/lockdep.c:3602>] lock_acquire+0x182/0x1d0
	 [<kernel/locking/mutex.c:470 kernel/locking/mutex.c:571>] mutex_lock_nested+0x6a/0x510
	 [<fs/kernfs/file.c:487>] kernfs_fop_mmap+0x54/0x120
	 [<mm/mmap.c:1573>] mmap_region+0x310/0x5c0
	 [<mm/mmap.c:1365>] do_mmap_pgoff+0x385/0x430
	 [<mm/util.c:399>] vm_mmap_pgoff+0x8f/0xe0
	 [<mm/mmap.c:1416 mm/mmap.c:1374>] SyS_mmap_pgoff+0x1b0/0x210
	 [<arch/x86/kernel/sys_x86_64.c:72>] SyS_mmap+0x1d/0x20
	 [<arch/x86/kernel/entry_64.S:749>] tracesys+0xdd/0xe2

  other info that might help us debug this:

   Possible unsafe locking scenario:

	 CPU0                    CPU1
	 ----                    ----
    lock(&mm->mmap_sem);
				 lock(&of->mutex#2);
				 lock(&mm->mmap_sem);
    lock(&of->mutex#2);

   *** DEADLOCK ***

  1 lock held by trinity-c236/10658:
   #0:  (&mm->mmap_sem){++++++}, at: [<mm/util.c:397>] vm_mmap_pgoff+0x6e/0xe0

  stack backtrace:
  CPU: 2 PID: 10658 Comm: trinity-c236 Tainted: G        W 3.14.0-rc4-next-20140228-sasha-00011-g4077c67-dirty #26
   0000000000000000 ffff88011911fa48 ffffffff8438e945 0000000000000000
   0000000000000000 ffff88011911fa98 ffffffff811a0109 ffff88011911fab8
   ffff88011911fab8 ffff88011911fa98 ffff880119128cc0 ffff880119128cf8
  Call Trace:
   [<lib/dump_stack.c:52>] dump_stack+0x52/0x7f
   [<kernel/locking/lockdep.c:1213>] print_circular_bug+0x129/0x160
   [<kernel/locking/lockdep.c:1840>] check_prev_add+0x13f/0x560
   [<include/linux/spinlock.h:343 mm/slub.c:1933>] ? deactivate_slab+0x511/0x550
   [<kernel/locking/lockdep.c:1945 kernel/locking/lockdep.c:2131>] validate_chain+0x6c5/0x7b0
   [<kernel/locking/lockdep.c:3182>] __lock_acquire+0x4cd/0x5a0
   [<mm/mmap.c:1552>] ? mmap_region+0x24a/0x5c0
   [<arch/x86/include/asm/current.h:14 kernel/locking/lockdep.c:3602>] lock_acquire+0x182/0x1d0
   [<fs/kernfs/file.c:487>] ? kernfs_fop_mmap+0x54/0x120
   [<kernel/locking/mutex.c:470 kernel/locking/mutex.c:571>] mutex_lock_nested+0x6a/0x510
   [<fs/kernfs/file.c:487>] ? kernfs_fop_mmap+0x54/0x120
   [<kernel/sched/core.c:2477>] ? get_parent_ip+0x11/0x50
   [<fs/kernfs/file.c:487>] ? kernfs_fop_mmap+0x54/0x120
   [<fs/kernfs/file.c:487>] kernfs_fop_mmap+0x54/0x120
   [<mm/mmap.c:1573>] mmap_region+0x310/0x5c0
   [<mm/mmap.c:1365>] do_mmap_pgoff+0x385/0x430
   [<mm/util.c:397>] ? vm_mmap_pgoff+0x6e/0xe0
   [<mm/util.c:399>] vm_mmap_pgoff+0x8f/0xe0
   [<kernel/rcu/update.c:97>] ? __rcu_read_unlock+0x44/0xb0
   [<fs/file.c:641>] ? dup_fd+0x3c0/0x3c0
   [<mm/mmap.c:1416 mm/mmap.c:1374>] SyS_mmap_pgoff+0x1b0/0x210
   [<arch/x86/kernel/sys_x86_64.c:72>] SyS_mmap+0x1d/0x20
   [<arch/x86/kernel/entry_64.S:749>] tracesys+0xdd/0xe2

Fix it by caching atomic_write_len in kernfs_open_file during open so
that it can be determined without accessing kernfs_ops in
kernfs_fop_write().  This restores the structure of kernfs_fop_write()
before 4d3773c4bb with updated @len determination logic.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
References: http://lkml.kernel.org/g/53113485.2090407@oracle.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-03-08 22:08:29 -08:00

441 lines
13 KiB
C

/*
* kernfs.h - pseudo filesystem decoupled from vfs locking
*
* This file is released under the GPLv2.
*/
#ifndef __LINUX_KERNFS_H
#define __LINUX_KERNFS_H
#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/idr.h>
#include <linux/lockdep.h>
#include <linux/rbtree.h>
#include <linux/atomic.h>
#include <linux/wait.h>
struct file;
struct dentry;
struct iattr;
struct seq_file;
struct vm_area_struct;
struct super_block;
struct file_system_type;
struct kernfs_open_node;
struct kernfs_iattrs;
enum kernfs_node_type {
KERNFS_DIR = 0x0001,
KERNFS_FILE = 0x0002,
KERNFS_LINK = 0x0004,
};
#define KERNFS_TYPE_MASK 0x000f
#define KERNFS_FLAG_MASK ~KERNFS_TYPE_MASK
enum kernfs_node_flag {
KERNFS_ACTIVATED = 0x0010,
KERNFS_NS = 0x0020,
KERNFS_HAS_SEQ_SHOW = 0x0040,
KERNFS_HAS_MMAP = 0x0080,
KERNFS_LOCKDEP = 0x0100,
KERNFS_STATIC_NAME = 0x0200,
KERNFS_SUICIDAL = 0x0400,
KERNFS_SUICIDED = 0x0800,
};
/* @flags for kernfs_create_root() */
enum kernfs_root_flag {
KERNFS_ROOT_CREATE_DEACTIVATED = 0x0001,
};
/* type-specific structures for kernfs_node union members */
struct kernfs_elem_dir {
unsigned long subdirs;
/* children rbtree starts here and goes through kn->rb */
struct rb_root children;
/*
* The kernfs hierarchy this directory belongs to. This fits
* better directly in kernfs_node but is here to save space.
*/
struct kernfs_root *root;
};
struct kernfs_elem_symlink {
struct kernfs_node *target_kn;
};
struct kernfs_elem_attr {
const struct kernfs_ops *ops;
struct kernfs_open_node *open;
loff_t size;
};
/*
* kernfs_node - the building block of kernfs hierarchy. Each and every
* kernfs node is represented by single kernfs_node. Most fields are
* private to kernfs and shouldn't be accessed directly by kernfs users.
*
* As long as s_count reference is held, the kernfs_node itself is
* accessible. Dereferencing elem or any other outer entity requires
* active reference.
*/
struct kernfs_node {
atomic_t count;
atomic_t active;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif
/*
* Use kernfs_get_parent() and kernfs_name/path() instead of
* accessing the following two fields directly. If the node is
* never moved to a different parent, it is safe to access the
* parent directly.
*/
struct kernfs_node *parent;
const char *name;
struct rb_node rb;
const void *ns; /* namespace tag */
unsigned int hash; /* ns + name hash */
union {
struct kernfs_elem_dir dir;
struct kernfs_elem_symlink symlink;
struct kernfs_elem_attr attr;
};
void *priv;
unsigned short flags;
umode_t mode;
unsigned int ino;
struct kernfs_iattrs *iattr;
};
/*
* kernfs_syscall_ops may be specified on kernfs_create_root() to support
* syscalls. These optional callbacks are invoked on the matching syscalls
* and can perform any kernfs operations which don't necessarily have to be
* the exact operation requested. An active reference is held for each
* kernfs_node parameter.
*/
struct kernfs_syscall_ops {
int (*remount_fs)(struct kernfs_root *root, int *flags, char *data);
int (*show_options)(struct seq_file *sf, struct kernfs_root *root);
int (*mkdir)(struct kernfs_node *parent, const char *name,
umode_t mode);
int (*rmdir)(struct kernfs_node *kn);
int (*rename)(struct kernfs_node *kn, struct kernfs_node *new_parent,
const char *new_name);
};
struct kernfs_root {
/* published fields */
struct kernfs_node *kn;
unsigned int flags; /* KERNFS_ROOT_* flags */
/* private fields, do not use outside kernfs proper */
struct ida ino_ida;
struct kernfs_syscall_ops *syscall_ops;
wait_queue_head_t deactivate_waitq;
};
struct kernfs_open_file {
/* published fields */
struct kernfs_node *kn;
struct file *file;
void *priv;
/* private fields, do not use outside kernfs proper */
struct mutex mutex;
int event;
struct list_head list;
size_t atomic_write_len;
bool mmapped;
const struct vm_operations_struct *vm_ops;
};
struct kernfs_ops {
/*
* Read is handled by either seq_file or raw_read().
*
* If seq_show() is present, seq_file path is active. Other seq
* operations are optional and if not implemented, the behavior is
* equivalent to single_open(). @sf->private points to the
* associated kernfs_open_file.
*
* read() is bounced through kernel buffer and a read larger than
* PAGE_SIZE results in partial operation of PAGE_SIZE.
*/
int (*seq_show)(struct seq_file *sf, void *v);
void *(*seq_start)(struct seq_file *sf, loff_t *ppos);
void *(*seq_next)(struct seq_file *sf, void *v, loff_t *ppos);
void (*seq_stop)(struct seq_file *sf, void *v);
ssize_t (*read)(struct kernfs_open_file *of, char *buf, size_t bytes,
loff_t off);
/*
* write() is bounced through kernel buffer. If atomic_write_len
* is not set, a write larger than PAGE_SIZE results in partial
* operations of PAGE_SIZE chunks. If atomic_write_len is set,
* writes upto the specified size are executed atomically but
* larger ones are rejected with -E2BIG.
*/
size_t atomic_write_len;
ssize_t (*write)(struct kernfs_open_file *of, char *buf, size_t bytes,
loff_t off);
int (*mmap)(struct kernfs_open_file *of, struct vm_area_struct *vma);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lock_class_key lockdep_key;
#endif
};
#ifdef CONFIG_KERNFS
static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
{
return kn->flags & KERNFS_TYPE_MASK;
}
/**
* kernfs_enable_ns - enable namespace under a directory
* @kn: directory of interest, should be empty
*
* This is to be called right after @kn is created to enable namespace
* under it. All children of @kn must have non-NULL namespace tags and
* only the ones which match the super_block's tag will be visible.
*/
static inline void kernfs_enable_ns(struct kernfs_node *kn)
{
WARN_ON_ONCE(kernfs_type(kn) != KERNFS_DIR);
WARN_ON_ONCE(!RB_EMPTY_ROOT(&kn->dir.children));
kn->flags |= KERNFS_NS;
}
/**
* kernfs_ns_enabled - test whether namespace is enabled
* @kn: the node to test
*
* Test whether namespace filtering is enabled for the children of @ns.
*/
static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
{
return kn->flags & KERNFS_NS;
}
int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
size_t buflen);
void pr_cont_kernfs_name(struct kernfs_node *kn);
void pr_cont_kernfs_path(struct kernfs_node *kn);
struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn);
struct kernfs_node *kernfs_find_and_get_ns(struct kernfs_node *parent,
const char *name, const void *ns);
void kernfs_get(struct kernfs_node *kn);
void kernfs_put(struct kernfs_node *kn);
struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry);
struct kernfs_root *kernfs_root_from_sb(struct super_block *sb);
struct kernfs_root *kernfs_create_root(struct kernfs_syscall_ops *scops,
unsigned int flags, void *priv);
void kernfs_destroy_root(struct kernfs_root *root);
struct kernfs_node *kernfs_create_dir_ns(struct kernfs_node *parent,
const char *name, umode_t mode,
void *priv, const void *ns);
struct kernfs_node *__kernfs_create_file(struct kernfs_node *parent,
const char *name,
umode_t mode, loff_t size,
const struct kernfs_ops *ops,
void *priv, const void *ns,
bool name_is_static,
struct lock_class_key *key);
struct kernfs_node *kernfs_create_link(struct kernfs_node *parent,
const char *name,
struct kernfs_node *target);
void kernfs_activate(struct kernfs_node *kn);
void kernfs_remove(struct kernfs_node *kn);
void kernfs_break_active_protection(struct kernfs_node *kn);
void kernfs_unbreak_active_protection(struct kernfs_node *kn);
bool kernfs_remove_self(struct kernfs_node *kn);
int kernfs_remove_by_name_ns(struct kernfs_node *parent, const char *name,
const void *ns);
int kernfs_rename_ns(struct kernfs_node *kn, struct kernfs_node *new_parent,
const char *new_name, const void *new_ns);
int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr);
void kernfs_notify(struct kernfs_node *kn);
const void *kernfs_super_ns(struct super_block *sb);
struct dentry *kernfs_mount_ns(struct file_system_type *fs_type, int flags,
struct kernfs_root *root, bool *new_sb_created,
const void *ns);
void kernfs_kill_sb(struct super_block *sb);
void kernfs_init(void);
#else /* CONFIG_KERNFS */
static inline enum kernfs_node_type kernfs_type(struct kernfs_node *kn)
{ return 0; } /* whatever */
static inline void kernfs_enable_ns(struct kernfs_node *kn) { }
static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
{ return false; }
static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
{ return -ENOSYS; }
static inline char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
size_t buflen)
{ return NULL; }
static inline void pr_cont_kernfs_name(struct kernfs_node *kn) { }
static inline void pr_cont_kernfs_path(struct kernfs_node *kn) { }
static inline struct kernfs_node *kernfs_get_parent(struct kernfs_node *kn)
{ return NULL; }
static inline struct kernfs_node *
kernfs_find_and_get_ns(struct kernfs_node *parent, const char *name,
const void *ns)
{ return NULL; }
static inline void kernfs_get(struct kernfs_node *kn) { }
static inline void kernfs_put(struct kernfs_node *kn) { }
static inline struct kernfs_node *kernfs_node_from_dentry(struct dentry *dentry)
{ return NULL; }
static inline struct kernfs_root *kernfs_root_from_sb(struct super_block *sb)
{ return NULL; }
static inline struct kernfs_root *
kernfs_create_root(struct kernfs_syscall_ops *scops, unsigned int flags,
void *priv)
{ return ERR_PTR(-ENOSYS); }
static inline void kernfs_destroy_root(struct kernfs_root *root) { }
static inline struct kernfs_node *
kernfs_create_dir_ns(struct kernfs_node *parent, const char *name,
umode_t mode, void *priv, const void *ns)
{ return ERR_PTR(-ENOSYS); }
static inline struct kernfs_node *
__kernfs_create_file(struct kernfs_node *parent, const char *name,
umode_t mode, loff_t size, const struct kernfs_ops *ops,
void *priv, const void *ns, bool name_is_static,
struct lock_class_key *key)
{ return ERR_PTR(-ENOSYS); }
static inline struct kernfs_node *
kernfs_create_link(struct kernfs_node *parent, const char *name,
struct kernfs_node *target)
{ return ERR_PTR(-ENOSYS); }
static inline void kernfs_activate(struct kernfs_node *kn) { }
static inline void kernfs_remove(struct kernfs_node *kn) { }
static inline bool kernfs_remove_self(struct kernfs_node *kn)
{ return false; }
static inline int kernfs_remove_by_name_ns(struct kernfs_node *kn,
const char *name, const void *ns)
{ return -ENOSYS; }
static inline int kernfs_rename_ns(struct kernfs_node *kn,
struct kernfs_node *new_parent,
const char *new_name, const void *new_ns)
{ return -ENOSYS; }
static inline int kernfs_setattr(struct kernfs_node *kn,
const struct iattr *iattr)
{ return -ENOSYS; }
static inline void kernfs_notify(struct kernfs_node *kn) { }
static inline const void *kernfs_super_ns(struct super_block *sb)
{ return NULL; }
static inline struct dentry *
kernfs_mount_ns(struct file_system_type *fs_type, int flags,
struct kernfs_root *root, bool *new_sb_created, const void *ns)
{ return ERR_PTR(-ENOSYS); }
static inline void kernfs_kill_sb(struct super_block *sb) { }
static inline void kernfs_init(void) { }
#endif /* CONFIG_KERNFS */
static inline struct kernfs_node *
kernfs_find_and_get(struct kernfs_node *kn, const char *name)
{
return kernfs_find_and_get_ns(kn, name, NULL);
}
static inline struct kernfs_node *
kernfs_create_dir(struct kernfs_node *parent, const char *name, umode_t mode,
void *priv)
{
return kernfs_create_dir_ns(parent, name, mode, priv, NULL);
}
static inline struct kernfs_node *
kernfs_create_file_ns(struct kernfs_node *parent, const char *name,
umode_t mode, loff_t size, const struct kernfs_ops *ops,
void *priv, const void *ns)
{
struct lock_class_key *key = NULL;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
key = (struct lock_class_key *)&ops->lockdep_key;
#endif
return __kernfs_create_file(parent, name, mode, size, ops, priv, ns,
false, key);
}
static inline struct kernfs_node *
kernfs_create_file(struct kernfs_node *parent, const char *name, umode_t mode,
loff_t size, const struct kernfs_ops *ops, void *priv)
{
return kernfs_create_file_ns(parent, name, mode, size, ops, priv, NULL);
}
static inline int kernfs_remove_by_name(struct kernfs_node *parent,
const char *name)
{
return kernfs_remove_by_name_ns(parent, name, NULL);
}
static inline int kernfs_rename(struct kernfs_node *kn,
struct kernfs_node *new_parent,
const char *new_name)
{
return kernfs_rename_ns(kn, new_parent, new_name, NULL);
}
static inline struct dentry *
kernfs_mount(struct file_system_type *fs_type, int flags,
struct kernfs_root *root, bool *new_sb_created)
{
return kernfs_mount_ns(fs_type, flags, root, new_sb_created, NULL);
}
#endif /* __LINUX_KERNFS_H */