linux/fs/exec.c
David Howells d84f4f992c CRED: Inaugurate COW credentials
Inaugurate copy-on-write credentials management.  This uses RCU to manage the
credentials pointer in the task_struct with respect to accesses by other tasks.
A process may only modify its own credentials, and so does not need locking to
access or modify its own credentials.

A mutex (cred_replace_mutex) is added to the task_struct to control the effect
of PTRACE_ATTACHED on credential calculations, particularly with respect to
execve().

With this patch, the contents of an active credentials struct may not be
changed directly; rather a new set of credentials must be prepared, modified
and committed using something like the following sequence of events:

	struct cred *new = prepare_creds();
	int ret = blah(new);
	if (ret < 0) {
		abort_creds(new);
		return ret;
	}
	return commit_creds(new);

There are some exceptions to this rule: the keyrings pointed to by the active
credentials may be instantiated - keyrings violate the COW rule as managing
COW keyrings is tricky, given that it is possible for a task to directly alter
the keys in a keyring in use by another task.

To help enforce this, various pointers to sets of credentials, such as those in
the task_struct, are declared const.  The purpose of this is compile-time
discouragement of altering credentials through those pointers.  Once a set of
credentials has been made public through one of these pointers, it may not be
modified, except under special circumstances:

  (1) Its reference count may incremented and decremented.

  (2) The keyrings to which it points may be modified, but not replaced.

The only safe way to modify anything else is to create a replacement and commit
using the functions described in Documentation/credentials.txt (which will be
added by a later patch).

This patch and the preceding patches have been tested with the LTP SELinux
testsuite.

This patch makes several logical sets of alteration:

 (1) execve().

     This now prepares and commits credentials in various places in the
     security code rather than altering the current creds directly.

 (2) Temporary credential overrides.

     do_coredump() and sys_faccessat() now prepare their own credentials and
     temporarily override the ones currently on the acting thread, whilst
     preventing interference from other threads by holding cred_replace_mutex
     on the thread being dumped.

     This will be replaced in a future patch by something that hands down the
     credentials directly to the functions being called, rather than altering
     the task's objective credentials.

 (3) LSM interface.

     A number of functions have been changed, added or removed:

     (*) security_capset_check(), ->capset_check()
     (*) security_capset_set(), ->capset_set()

     	 Removed in favour of security_capset().

     (*) security_capset(), ->capset()

     	 New.  This is passed a pointer to the new creds, a pointer to the old
     	 creds and the proposed capability sets.  It should fill in the new
     	 creds or return an error.  All pointers, barring the pointer to the
     	 new creds, are now const.

     (*) security_bprm_apply_creds(), ->bprm_apply_creds()

     	 Changed; now returns a value, which will cause the process to be
     	 killed if it's an error.

     (*) security_task_alloc(), ->task_alloc_security()

     	 Removed in favour of security_prepare_creds().

     (*) security_cred_free(), ->cred_free()

     	 New.  Free security data attached to cred->security.

     (*) security_prepare_creds(), ->cred_prepare()

     	 New. Duplicate any security data attached to cred->security.

     (*) security_commit_creds(), ->cred_commit()

     	 New. Apply any security effects for the upcoming installation of new
     	 security by commit_creds().

     (*) security_task_post_setuid(), ->task_post_setuid()

     	 Removed in favour of security_task_fix_setuid().

     (*) security_task_fix_setuid(), ->task_fix_setuid()

     	 Fix up the proposed new credentials for setuid().  This is used by
     	 cap_set_fix_setuid() to implicitly adjust capabilities in line with
     	 setuid() changes.  Changes are made to the new credentials, rather
     	 than the task itself as in security_task_post_setuid().

     (*) security_task_reparent_to_init(), ->task_reparent_to_init()

     	 Removed.  Instead the task being reparented to init is referred
     	 directly to init's credentials.

	 NOTE!  This results in the loss of some state: SELinux's osid no
	 longer records the sid of the thread that forked it.

     (*) security_key_alloc(), ->key_alloc()
     (*) security_key_permission(), ->key_permission()

     	 Changed.  These now take cred pointers rather than task pointers to
     	 refer to the security context.

 (4) sys_capset().

     This has been simplified and uses less locking.  The LSM functions it
     calls have been merged.

 (5) reparent_to_kthreadd().

     This gives the current thread the same credentials as init by simply using
     commit_thread() to point that way.

 (6) __sigqueue_alloc() and switch_uid()

     __sigqueue_alloc() can't stop the target task from changing its creds
     beneath it, so this function gets a reference to the currently applicable
     user_struct which it then passes into the sigqueue struct it returns if
     successful.

     switch_uid() is now called from commit_creds(), and possibly should be
     folded into that.  commit_creds() should take care of protecting
     __sigqueue_alloc().

 (7) [sg]et[ug]id() and co and [sg]et_current_groups.

     The set functions now all use prepare_creds(), commit_creds() and
     abort_creds() to build and check a new set of credentials before applying
     it.

     security_task_set[ug]id() is called inside the prepared section.  This
     guarantees that nothing else will affect the creds until we've finished.

     The calling of set_dumpable() has been moved into commit_creds().

     Much of the functionality of set_user() has been moved into
     commit_creds().

     The get functions all simply access the data directly.

 (8) security_task_prctl() and cap_task_prctl().

     security_task_prctl() has been modified to return -ENOSYS if it doesn't
     want to handle a function, or otherwise return the return value directly
     rather than through an argument.

     Additionally, cap_task_prctl() now prepares a new set of credentials, even
     if it doesn't end up using it.

 (9) Keyrings.

     A number of changes have been made to the keyrings code:

     (a) switch_uid_keyring(), copy_keys(), exit_keys() and suid_keys() have
     	 all been dropped and built in to the credentials functions directly.
     	 They may want separating out again later.

     (b) key_alloc() and search_process_keyrings() now take a cred pointer
     	 rather than a task pointer to specify the security context.

     (c) copy_creds() gives a new thread within the same thread group a new
     	 thread keyring if its parent had one, otherwise it discards the thread
     	 keyring.

     (d) The authorisation key now points directly to the credentials to extend
     	 the search into rather pointing to the task that carries them.

     (e) Installing thread, process or session keyrings causes a new set of
     	 credentials to be created, even though it's not strictly necessary for
     	 process or session keyrings (they're shared).

(10) Usermode helper.

     The usermode helper code now carries a cred struct pointer in its
     subprocess_info struct instead of a new session keyring pointer.  This set
     of credentials is derived from init_cred and installed on the new process
     after it has been cloned.

     call_usermodehelper_setup() allocates the new credentials and
     call_usermodehelper_freeinfo() discards them if they haven't been used.  A
     special cred function (prepare_usermodeinfo_creds()) is provided
     specifically for call_usermodehelper_setup() to call.

     call_usermodehelper_setkeys() adjusts the credentials to sport the
     supplied keyring as the new session keyring.

(11) SELinux.

     SELinux has a number of changes, in addition to those to support the LSM
     interface changes mentioned above:

     (a) selinux_setprocattr() no longer does its check for whether the
     	 current ptracer can access processes with the new SID inside the lock
     	 that covers getting the ptracer's SID.  Whilst this lock ensures that
     	 the check is done with the ptracer pinned, the result is only valid
     	 until the lock is released, so there's no point doing it inside the
     	 lock.

(12) is_single_threaded().

     This function has been extracted from selinux_setprocattr() and put into
     a file of its own in the lib/ directory as join_session_keyring() now
     wants to use it too.

     The code in SELinux just checked to see whether a task shared mm_structs
     with other tasks (CLONE_VM), but that isn't good enough.  We really want
     to know if they're part of the same thread group (CLONE_THREAD).

(13) nfsd.

     The NFS server daemon now has to use the COW credentials to set the
     credentials it is going to use.  It really needs to pass the credentials
     down to the functions it calls, but it can't do that until other patches
     in this series have been applied.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: James Morris <jmorris@namei.org>
Signed-off-by: James Morris <jmorris@namei.org>
2008-11-14 10:39:23 +11:00

1854 lines
42 KiB
C

/*
* linux/fs/exec.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/
/*
* #!-checking implemented by tytso.
*/
/*
* Demand-loading implemented 01.12.91 - no need to read anything but
* the header into memory. The inode of the executable is put into
* "current->executable", and page faults do the actual loading. Clean.
*
* Once more I can proudly say that linux stood up to being changed: it
* was less than 2 hours work to get demand-loading completely implemented.
*
* Demand loading changed July 1993 by Eric Youngdale. Use mmap instead,
* current->executable is only used by the procfs. This allows a dispatch
* table to check for several different types of binary formats. We keep
* trying until we recognize the file or we run out of supported binary
* formats.
*/
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/mm.h>
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/smp_lock.h>
#include <linux/swap.h>
#include <linux/string.h>
#include <linux/init.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/spinlock.h>
#include <linux/key.h>
#include <linux/personality.h>
#include <linux/binfmts.h>
#include <linux/utsname.h>
#include <linux/pid_namespace.h>
#include <linux/module.h>
#include <linux/namei.h>
#include <linux/proc_fs.h>
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/tsacct_kern.h>
#include <linux/cn_proc.h>
#include <linux/audit.h>
#include <linux/tracehook.h>
#include <linux/kmod.h>
#include <asm/uaccess.h>
#include <asm/mmu_context.h>
#include <asm/tlb.h>
#ifdef __alpha__
/* for /sbin/loader handling in search_binary_handler() */
#include <linux/a.out.h>
#endif
int core_uses_pid;
char core_pattern[CORENAME_MAX_SIZE] = "core";
int suid_dumpable = 0;
/* The maximal length of core_pattern is also specified in sysctl.c */
static LIST_HEAD(formats);
static DEFINE_RWLOCK(binfmt_lock);
int register_binfmt(struct linux_binfmt * fmt)
{
if (!fmt)
return -EINVAL;
write_lock(&binfmt_lock);
list_add(&fmt->lh, &formats);
write_unlock(&binfmt_lock);
return 0;
}
EXPORT_SYMBOL(register_binfmt);
void unregister_binfmt(struct linux_binfmt * fmt)
{
write_lock(&binfmt_lock);
list_del(&fmt->lh);
write_unlock(&binfmt_lock);
}
EXPORT_SYMBOL(unregister_binfmt);
static inline void put_binfmt(struct linux_binfmt * fmt)
{
module_put(fmt->module);
}
/*
* Note that a shared library must be both readable and executable due to
* security reasons.
*
* Also note that we take the address to load from from the file itself.
*/
asmlinkage long sys_uselib(const char __user * library)
{
struct file *file;
struct nameidata nd;
char *tmp = getname(library);
int error = PTR_ERR(tmp);
if (!IS_ERR(tmp)) {
error = path_lookup_open(AT_FDCWD, tmp,
LOOKUP_FOLLOW, &nd,
FMODE_READ|FMODE_EXEC);
putname(tmp);
}
if (error)
goto out;
error = -EINVAL;
if (!S_ISREG(nd.path.dentry->d_inode->i_mode))
goto exit;
error = -EACCES;
if (nd.path.mnt->mnt_flags & MNT_NOEXEC)
goto exit;
error = vfs_permission(&nd, MAY_READ | MAY_EXEC | MAY_OPEN);
if (error)
goto exit;
file = nameidata_to_filp(&nd, O_RDONLY|O_LARGEFILE);
error = PTR_ERR(file);
if (IS_ERR(file))
goto out;
error = -ENOEXEC;
if(file->f_op) {
struct linux_binfmt * fmt;
read_lock(&binfmt_lock);
list_for_each_entry(fmt, &formats, lh) {
if (!fmt->load_shlib)
continue;
if (!try_module_get(fmt->module))
continue;
read_unlock(&binfmt_lock);
error = fmt->load_shlib(file);
read_lock(&binfmt_lock);
put_binfmt(fmt);
if (error != -ENOEXEC)
break;
}
read_unlock(&binfmt_lock);
}
fput(file);
out:
return error;
exit:
release_open_intent(&nd);
path_put(&nd.path);
goto out;
}
#ifdef CONFIG_MMU
static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
int write)
{
struct page *page;
int ret;
#ifdef CONFIG_STACK_GROWSUP
if (write) {
ret = expand_stack_downwards(bprm->vma, pos);
if (ret < 0)
return NULL;
}
#endif
ret = get_user_pages(current, bprm->mm, pos,
1, write, 1, &page, NULL);
if (ret <= 0)
return NULL;
if (write) {
unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
struct rlimit *rlim;
/*
* We've historically supported up to 32 pages (ARG_MAX)
* of argument strings even with small stacks
*/
if (size <= ARG_MAX)
return page;
/*
* Limit to 1/4-th the stack size for the argv+env strings.
* This ensures that:
* - the remaining binfmt code will not run out of stack space,
* - the program will have a reasonable amount of stack left
* to work from.
*/
rlim = current->signal->rlim;
if (size > rlim[RLIMIT_STACK].rlim_cur / 4) {
put_page(page);
return NULL;
}
}
return page;
}
static void put_arg_page(struct page *page)
{
put_page(page);
}
static void free_arg_page(struct linux_binprm *bprm, int i)
{
}
static void free_arg_pages(struct linux_binprm *bprm)
{
}
static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
struct page *page)
{
flush_cache_page(bprm->vma, pos, page_to_pfn(page));
}
static int __bprm_mm_init(struct linux_binprm *bprm)
{
int err = -ENOMEM;
struct vm_area_struct *vma = NULL;
struct mm_struct *mm = bprm->mm;
bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
if (!vma)
goto err;
down_write(&mm->mmap_sem);
vma->vm_mm = mm;
/*
* Place the stack at the largest stack address the architecture
* supports. Later, we'll move this to an appropriate place. We don't
* use STACK_TOP because that can depend on attributes which aren't
* configured yet.
*/
vma->vm_end = STACK_TOP_MAX;
vma->vm_start = vma->vm_end - PAGE_SIZE;
vma->vm_flags = VM_STACK_FLAGS;
vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
err = insert_vm_struct(mm, vma);
if (err) {
up_write(&mm->mmap_sem);
goto err;
}
mm->stack_vm = mm->total_vm = 1;
up_write(&mm->mmap_sem);
bprm->p = vma->vm_end - sizeof(void *);
return 0;
err:
if (vma) {
bprm->vma = NULL;
kmem_cache_free(vm_area_cachep, vma);
}
return err;
}
static bool valid_arg_len(struct linux_binprm *bprm, long len)
{
return len <= MAX_ARG_STRLEN;
}
#else
static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
int write)
{
struct page *page;
page = bprm->page[pos / PAGE_SIZE];
if (!page && write) {
page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
if (!page)
return NULL;
bprm->page[pos / PAGE_SIZE] = page;
}
return page;
}
static void put_arg_page(struct page *page)
{
}
static void free_arg_page(struct linux_binprm *bprm, int i)
{
if (bprm->page[i]) {
__free_page(bprm->page[i]);
bprm->page[i] = NULL;
}
}
static void free_arg_pages(struct linux_binprm *bprm)
{
int i;
for (i = 0; i < MAX_ARG_PAGES; i++)
free_arg_page(bprm, i);
}
static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
struct page *page)
{
}
static int __bprm_mm_init(struct linux_binprm *bprm)
{
bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
return 0;
}
static bool valid_arg_len(struct linux_binprm *bprm, long len)
{
return len <= bprm->p;
}
#endif /* CONFIG_MMU */
/*
* Create a new mm_struct and populate it with a temporary stack
* vm_area_struct. We don't have enough context at this point to set the stack
* flags, permissions, and offset, so we use temporary values. We'll update
* them later in setup_arg_pages().
*/
int bprm_mm_init(struct linux_binprm *bprm)
{
int err;
struct mm_struct *mm = NULL;
bprm->mm = mm = mm_alloc();
err = -ENOMEM;
if (!mm)
goto err;
err = init_new_context(current, mm);
if (err)
goto err;
err = __bprm_mm_init(bprm);
if (err)
goto err;
return 0;
err:
if (mm) {
bprm->mm = NULL;
mmdrop(mm);
}
return err;
}
/*
* count() counts the number of strings in array ARGV.
*/
static int count(char __user * __user * argv, int max)
{
int i = 0;
if (argv != NULL) {
for (;;) {
char __user * p;
if (get_user(p, argv))
return -EFAULT;
if (!p)
break;
argv++;
if (i++ >= max)
return -E2BIG;
cond_resched();
}
}
return i;
}
/*
* 'copy_strings()' copies argument/environment strings from the old
* processes's memory to the new process's stack. The call to get_user_pages()
* ensures the destination page is created and not swapped out.
*/
static int copy_strings(int argc, char __user * __user * argv,
struct linux_binprm *bprm)
{
struct page *kmapped_page = NULL;
char *kaddr = NULL;
unsigned long kpos = 0;
int ret;
while (argc-- > 0) {
char __user *str;
int len;
unsigned long pos;
if (get_user(str, argv+argc) ||
!(len = strnlen_user(str, MAX_ARG_STRLEN))) {
ret = -EFAULT;
goto out;
}
if (!valid_arg_len(bprm, len)) {
ret = -E2BIG;
goto out;
}
/* We're going to work our way backwords. */
pos = bprm->p;
str += len;
bprm->p -= len;
while (len > 0) {
int offset, bytes_to_copy;
offset = pos % PAGE_SIZE;
if (offset == 0)
offset = PAGE_SIZE;
bytes_to_copy = offset;
if (bytes_to_copy > len)
bytes_to_copy = len;
offset -= bytes_to_copy;
pos -= bytes_to_copy;
str -= bytes_to_copy;
len -= bytes_to_copy;
if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
struct page *page;
page = get_arg_page(bprm, pos, 1);
if (!page) {
ret = -E2BIG;
goto out;
}
if (kmapped_page) {
flush_kernel_dcache_page(kmapped_page);
kunmap(kmapped_page);
put_arg_page(kmapped_page);
}
kmapped_page = page;
kaddr = kmap(kmapped_page);
kpos = pos & PAGE_MASK;
flush_arg_page(bprm, kpos, kmapped_page);
}
if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
ret = -EFAULT;
goto out;
}
}
}
ret = 0;
out:
if (kmapped_page) {
flush_kernel_dcache_page(kmapped_page);
kunmap(kmapped_page);
put_arg_page(kmapped_page);
}
return ret;
}
/*
* Like copy_strings, but get argv and its values from kernel memory.
*/
int copy_strings_kernel(int argc,char ** argv, struct linux_binprm *bprm)
{
int r;
mm_segment_t oldfs = get_fs();
set_fs(KERNEL_DS);
r = copy_strings(argc, (char __user * __user *)argv, bprm);
set_fs(oldfs);
return r;
}
EXPORT_SYMBOL(copy_strings_kernel);
#ifdef CONFIG_MMU
/*
* During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX. Once
* the binfmt code determines where the new stack should reside, we shift it to
* its final location. The process proceeds as follows:
*
* 1) Use shift to calculate the new vma endpoints.
* 2) Extend vma to cover both the old and new ranges. This ensures the
* arguments passed to subsequent functions are consistent.
* 3) Move vma's page tables to the new range.
* 4) Free up any cleared pgd range.
* 5) Shrink the vma to cover only the new range.
*/
static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long old_start = vma->vm_start;
unsigned long old_end = vma->vm_end;
unsigned long length = old_end - old_start;
unsigned long new_start = old_start - shift;
unsigned long new_end = old_end - shift;
struct mmu_gather *tlb;
BUG_ON(new_start > new_end);
/*
* ensure there are no vmas between where we want to go
* and where we are
*/
if (vma != find_vma(mm, new_start))
return -EFAULT;
/*
* cover the whole range: [new_start, old_end)
*/
vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL);
/*
* move the page tables downwards, on failure we rely on
* process cleanup to remove whatever mess we made.
*/
if (length != move_page_tables(vma, old_start,
vma, new_start, length))
return -ENOMEM;
lru_add_drain();
tlb = tlb_gather_mmu(mm, 0);
if (new_end > old_start) {
/*
* when the old and new regions overlap clear from new_end.
*/
free_pgd_range(tlb, new_end, old_end, new_end,
vma->vm_next ? vma->vm_next->vm_start : 0);
} else {
/*
* otherwise, clean from old_start; this is done to not touch
* the address space in [new_end, old_start) some architectures
* have constraints on va-space that make this illegal (IA64) -
* for the others its just a little faster.
*/
free_pgd_range(tlb, old_start, old_end, new_end,
vma->vm_next ? vma->vm_next->vm_start : 0);
}
tlb_finish_mmu(tlb, new_end, old_end);
/*
* shrink the vma to just the new range.
*/
vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
return 0;
}
#define EXTRA_STACK_VM_PAGES 20 /* random */
/*
* Finalizes the stack vm_area_struct. The flags and permissions are updated,
* the stack is optionally relocated, and some extra space is added.
*/
int setup_arg_pages(struct linux_binprm *bprm,
unsigned long stack_top,
int executable_stack)
{
unsigned long ret;
unsigned long stack_shift;
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma = bprm->vma;
struct vm_area_struct *prev = NULL;
unsigned long vm_flags;
unsigned long stack_base;
#ifdef CONFIG_STACK_GROWSUP
/* Limit stack size to 1GB */
stack_base = current->signal->rlim[RLIMIT_STACK].rlim_max;
if (stack_base > (1 << 30))
stack_base = 1 << 30;
/* Make sure we didn't let the argument array grow too large. */
if (vma->vm_end - vma->vm_start > stack_base)
return -ENOMEM;
stack_base = PAGE_ALIGN(stack_top - stack_base);
stack_shift = vma->vm_start - stack_base;
mm->arg_start = bprm->p - stack_shift;
bprm->p = vma->vm_end - stack_shift;
#else
stack_top = arch_align_stack(stack_top);
stack_top = PAGE_ALIGN(stack_top);
stack_shift = vma->vm_end - stack_top;
bprm->p -= stack_shift;
mm->arg_start = bprm->p;
#endif
if (bprm->loader)
bprm->loader -= stack_shift;
bprm->exec -= stack_shift;
down_write(&mm->mmap_sem);
vm_flags = VM_STACK_FLAGS;
/*
* Adjust stack execute permissions; explicitly enable for
* EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
* (arch default) otherwise.
*/
if (unlikely(executable_stack == EXSTACK_ENABLE_X))
vm_flags |= VM_EXEC;
else if (executable_stack == EXSTACK_DISABLE_X)
vm_flags &= ~VM_EXEC;
vm_flags |= mm->def_flags;
ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
vm_flags);
if (ret)
goto out_unlock;
BUG_ON(prev != vma);
/* Move stack pages down in memory. */
if (stack_shift) {
ret = shift_arg_pages(vma, stack_shift);
if (ret) {
up_write(&mm->mmap_sem);
return ret;
}
}
#ifdef CONFIG_STACK_GROWSUP
stack_base = vma->vm_end + EXTRA_STACK_VM_PAGES * PAGE_SIZE;
#else
stack_base = vma->vm_start - EXTRA_STACK_VM_PAGES * PAGE_SIZE;
#endif
ret = expand_stack(vma, stack_base);
if (ret)
ret = -EFAULT;
out_unlock:
up_write(&mm->mmap_sem);
return 0;
}
EXPORT_SYMBOL(setup_arg_pages);
#endif /* CONFIG_MMU */
struct file *open_exec(const char *name)
{
struct nameidata nd;
struct file *file;
int err;
err = path_lookup_open(AT_FDCWD, name, LOOKUP_FOLLOW, &nd,
FMODE_READ|FMODE_EXEC);
if (err)
goto out;
err = -EACCES;
if (!S_ISREG(nd.path.dentry->d_inode->i_mode))
goto out_path_put;
if (nd.path.mnt->mnt_flags & MNT_NOEXEC)
goto out_path_put;
err = vfs_permission(&nd, MAY_EXEC | MAY_OPEN);
if (err)
goto out_path_put;
file = nameidata_to_filp(&nd, O_RDONLY|O_LARGEFILE);
if (IS_ERR(file))
return file;
err = deny_write_access(file);
if (err) {
fput(file);
goto out;
}
return file;
out_path_put:
release_open_intent(&nd);
path_put(&nd.path);
out:
return ERR_PTR(err);
}
EXPORT_SYMBOL(open_exec);
int kernel_read(struct file *file, unsigned long offset,
char *addr, unsigned long count)
{
mm_segment_t old_fs;
loff_t pos = offset;
int result;
old_fs = get_fs();
set_fs(get_ds());
/* The cast to a user pointer is valid due to the set_fs() */
result = vfs_read(file, (void __user *)addr, count, &pos);
set_fs(old_fs);
return result;
}
EXPORT_SYMBOL(kernel_read);
static int exec_mmap(struct mm_struct *mm)
{
struct task_struct *tsk;
struct mm_struct * old_mm, *active_mm;
/* Notify parent that we're no longer interested in the old VM */
tsk = current;
old_mm = current->mm;
mm_release(tsk, old_mm);
if (old_mm) {
/*
* Make sure that if there is a core dump in progress
* for the old mm, we get out and die instead of going
* through with the exec. We must hold mmap_sem around
* checking core_state and changing tsk->mm.
*/
down_read(&old_mm->mmap_sem);
if (unlikely(old_mm->core_state)) {
up_read(&old_mm->mmap_sem);
return -EINTR;
}
}
task_lock(tsk);
active_mm = tsk->active_mm;
tsk->mm = mm;
tsk->active_mm = mm;
activate_mm(active_mm, mm);
task_unlock(tsk);
arch_pick_mmap_layout(mm);
if (old_mm) {
up_read(&old_mm->mmap_sem);
BUG_ON(active_mm != old_mm);
mm_update_next_owner(old_mm);
mmput(old_mm);
return 0;
}
mmdrop(active_mm);
return 0;
}
/*
* This function makes sure the current process has its own signal table,
* so that flush_signal_handlers can later reset the handlers without
* disturbing other processes. (Other processes might share the signal
* table via the CLONE_SIGHAND option to clone().)
*/
static int de_thread(struct task_struct *tsk)
{
struct signal_struct *sig = tsk->signal;
struct sighand_struct *oldsighand = tsk->sighand;
spinlock_t *lock = &oldsighand->siglock;
struct task_struct *leader = NULL;
int count;
if (thread_group_empty(tsk))
goto no_thread_group;
/*
* Kill all other threads in the thread group.
*/
spin_lock_irq(lock);
if (signal_group_exit(sig)) {
/*
* Another group action in progress, just
* return so that the signal is processed.
*/
spin_unlock_irq(lock);
return -EAGAIN;
}
sig->group_exit_task = tsk;
zap_other_threads(tsk);
/* Account for the thread group leader hanging around: */
count = thread_group_leader(tsk) ? 1 : 2;
sig->notify_count = count;
while (atomic_read(&sig->count) > count) {
__set_current_state(TASK_UNINTERRUPTIBLE);
spin_unlock_irq(lock);
schedule();
spin_lock_irq(lock);
}
spin_unlock_irq(lock);
/*
* At this point all other threads have exited, all we have to
* do is to wait for the thread group leader to become inactive,
* and to assume its PID:
*/
if (!thread_group_leader(tsk)) {
leader = tsk->group_leader;
sig->notify_count = -1; /* for exit_notify() */
for (;;) {
write_lock_irq(&tasklist_lock);
if (likely(leader->exit_state))
break;
__set_current_state(TASK_UNINTERRUPTIBLE);
write_unlock_irq(&tasklist_lock);
schedule();
}
/*
* The only record we have of the real-time age of a
* process, regardless of execs it's done, is start_time.
* All the past CPU time is accumulated in signal_struct
* from sister threads now dead. But in this non-leader
* exec, nothing survives from the original leader thread,
* whose birth marks the true age of this process now.
* When we take on its identity by switching to its PID, we
* also take its birthdate (always earlier than our own).
*/
tsk->start_time = leader->start_time;
BUG_ON(!same_thread_group(leader, tsk));
BUG_ON(has_group_leader_pid(tsk));
/*
* An exec() starts a new thread group with the
* TGID of the previous thread group. Rehash the
* two threads with a switched PID, and release
* the former thread group leader:
*/
/* Become a process group leader with the old leader's pid.
* The old leader becomes a thread of the this thread group.
* Note: The old leader also uses this pid until release_task
* is called. Odd but simple and correct.
*/
detach_pid(tsk, PIDTYPE_PID);
tsk->pid = leader->pid;
attach_pid(tsk, PIDTYPE_PID, task_pid(leader));
transfer_pid(leader, tsk, PIDTYPE_PGID);
transfer_pid(leader, tsk, PIDTYPE_SID);
list_replace_rcu(&leader->tasks, &tsk->tasks);
tsk->group_leader = tsk;
leader->group_leader = tsk;
tsk->exit_signal = SIGCHLD;
BUG_ON(leader->exit_state != EXIT_ZOMBIE);
leader->exit_state = EXIT_DEAD;
write_unlock_irq(&tasklist_lock);
}
sig->group_exit_task = NULL;
sig->notify_count = 0;
no_thread_group:
exit_itimers(sig);
flush_itimer_signals();
if (leader)
release_task(leader);
if (atomic_read(&oldsighand->count) != 1) {
struct sighand_struct *newsighand;
/*
* This ->sighand is shared with the CLONE_SIGHAND
* but not CLONE_THREAD task, switch to the new one.
*/
newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
if (!newsighand)
return -ENOMEM;
atomic_set(&newsighand->count, 1);
memcpy(newsighand->action, oldsighand->action,
sizeof(newsighand->action));
write_lock_irq(&tasklist_lock);
spin_lock(&oldsighand->siglock);
rcu_assign_pointer(tsk->sighand, newsighand);
spin_unlock(&oldsighand->siglock);
write_unlock_irq(&tasklist_lock);
__cleanup_sighand(oldsighand);
}
BUG_ON(!thread_group_leader(tsk));
return 0;
}
/*
* These functions flushes out all traces of the currently running executable
* so that a new one can be started
*/
static void flush_old_files(struct files_struct * files)
{
long j = -1;
struct fdtable *fdt;
spin_lock(&files->file_lock);
for (;;) {
unsigned long set, i;
j++;
i = j * __NFDBITS;
fdt = files_fdtable(files);
if (i >= fdt->max_fds)
break;
set = fdt->close_on_exec->fds_bits[j];
if (!set)
continue;
fdt->close_on_exec->fds_bits[j] = 0;
spin_unlock(&files->file_lock);
for ( ; set ; i++,set >>= 1) {
if (set & 1) {
sys_close(i);
}
}
spin_lock(&files->file_lock);
}
spin_unlock(&files->file_lock);
}
char *get_task_comm(char *buf, struct task_struct *tsk)
{
/* buf must be at least sizeof(tsk->comm) in size */
task_lock(tsk);
strncpy(buf, tsk->comm, sizeof(tsk->comm));
task_unlock(tsk);
return buf;
}
void set_task_comm(struct task_struct *tsk, char *buf)
{
task_lock(tsk);
strlcpy(tsk->comm, buf, sizeof(tsk->comm));
task_unlock(tsk);
}
int flush_old_exec(struct linux_binprm * bprm)
{
char * name;
int i, ch, retval;
char tcomm[sizeof(current->comm)];
/*
* Make sure we have a private signal table and that
* we are unassociated from the previous thread group.
*/
retval = de_thread(current);
if (retval)
goto out;
set_mm_exe_file(bprm->mm, bprm->file);
/*
* Release all of the old mmap stuff
*/
retval = exec_mmap(bprm->mm);
if (retval)
goto out;
bprm->mm = NULL; /* We're using it now */
/* This is the point of no return */
current->sas_ss_sp = current->sas_ss_size = 0;
if (current_euid() == current_uid() && current_egid() == current_gid())
set_dumpable(current->mm, 1);
else
set_dumpable(current->mm, suid_dumpable);
name = bprm->filename;
/* Copies the binary name from after last slash */
for (i=0; (ch = *(name++)) != '\0';) {
if (ch == '/')
i = 0; /* overwrite what we wrote */
else
if (i < (sizeof(tcomm) - 1))
tcomm[i++] = ch;
}
tcomm[i] = '\0';
set_task_comm(current, tcomm);
current->flags &= ~PF_RANDOMIZE;
flush_thread();
/* Set the new mm task size. We have to do that late because it may
* depend on TIF_32BIT which is only updated in flush_thread() on
* some architectures like powerpc
*/
current->mm->task_size = TASK_SIZE;
if (bprm->e_uid != current_euid() ||
bprm->e_gid != current_egid()) {
set_dumpable(current->mm, suid_dumpable);
current->pdeath_signal = 0;
} else if (file_permission(bprm->file, MAY_READ) ||
(bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP)) {
set_dumpable(current->mm, suid_dumpable);
}
/* An exec changes our domain. We are no longer part of the thread
group */
current->self_exec_id++;
flush_signal_handlers(current, 0);
flush_old_files(current->files);
return 0;
out:
return retval;
}
EXPORT_SYMBOL(flush_old_exec);
/*
* Fill the binprm structure from the inode.
* Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
*/
int prepare_binprm(struct linux_binprm *bprm)
{
int mode;
struct inode * inode = bprm->file->f_path.dentry->d_inode;
int retval;
mode = inode->i_mode;
if (bprm->file->f_op == NULL)
return -EACCES;
bprm->e_uid = current_euid();
bprm->e_gid = current_egid();
if(!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
/* Set-uid? */
if (mode & S_ISUID) {
current->personality &= ~PER_CLEAR_ON_SETID;
bprm->e_uid = inode->i_uid;
}
/* Set-gid? */
/*
* If setgid is set but no group execute bit then this
* is a candidate for mandatory locking, not a setgid
* executable.
*/
if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
current->personality &= ~PER_CLEAR_ON_SETID;
bprm->e_gid = inode->i_gid;
}
}
/* fill in binprm security blob */
retval = security_bprm_set(bprm);
if (retval)
return retval;
memset(bprm->buf,0,BINPRM_BUF_SIZE);
return kernel_read(bprm->file,0,bprm->buf,BINPRM_BUF_SIZE);
}
EXPORT_SYMBOL(prepare_binprm);
static int unsafe_exec(struct task_struct *p)
{
int unsafe = tracehook_unsafe_exec(p);
if (atomic_read(&p->fs->count) > 1 ||
atomic_read(&p->files->count) > 1 ||
atomic_read(&p->sighand->count) > 1)
unsafe |= LSM_UNSAFE_SHARE;
return unsafe;
}
void compute_creds(struct linux_binprm *bprm)
{
int unsafe;
if (bprm->e_uid != current_uid())
current->pdeath_signal = 0;
exec_keys(current);
task_lock(current);
unsafe = unsafe_exec(current);
security_bprm_apply_creds(bprm, unsafe);
task_unlock(current);
security_bprm_post_apply_creds(bprm);
}
EXPORT_SYMBOL(compute_creds);
/*
* Arguments are '\0' separated strings found at the location bprm->p
* points to; chop off the first by relocating brpm->p to right after
* the first '\0' encountered.
*/
int remove_arg_zero(struct linux_binprm *bprm)
{
int ret = 0;
unsigned long offset;
char *kaddr;
struct page *page;
if (!bprm->argc)
return 0;
do {
offset = bprm->p & ~PAGE_MASK;
page = get_arg_page(bprm, bprm->p, 0);
if (!page) {
ret = -EFAULT;
goto out;
}
kaddr = kmap_atomic(page, KM_USER0);
for (; offset < PAGE_SIZE && kaddr[offset];
offset++, bprm->p++)
;
kunmap_atomic(kaddr, KM_USER0);
put_arg_page(page);
if (offset == PAGE_SIZE)
free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
} while (offset == PAGE_SIZE);
bprm->p++;
bprm->argc--;
ret = 0;
out:
return ret;
}
EXPORT_SYMBOL(remove_arg_zero);
/*
* cycle the list of binary formats handler, until one recognizes the image
*/
int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
{
int try,retval;
struct linux_binfmt *fmt;
#ifdef __alpha__
/* handle /sbin/loader.. */
{
struct exec * eh = (struct exec *) bprm->buf;
if (!bprm->loader && eh->fh.f_magic == 0x183 &&
(eh->fh.f_flags & 0x3000) == 0x3000)
{
struct file * file;
unsigned long loader;
allow_write_access(bprm->file);
fput(bprm->file);
bprm->file = NULL;
loader = bprm->vma->vm_end - sizeof(void *);
file = open_exec("/sbin/loader");
retval = PTR_ERR(file);
if (IS_ERR(file))
return retval;
/* Remember if the application is TASO. */
bprm->taso = eh->ah.entry < 0x100000000UL;
bprm->file = file;
bprm->loader = loader;
retval = prepare_binprm(bprm);
if (retval<0)
return retval;
/* should call search_binary_handler recursively here,
but it does not matter */
}
}
#endif
retval = security_bprm_check(bprm);
if (retval)
return retval;
/* kernel module loader fixup */
/* so we don't try to load run modprobe in kernel space. */
set_fs(USER_DS);
retval = audit_bprm(bprm);
if (retval)
return retval;
retval = -ENOENT;
for (try=0; try<2; try++) {
read_lock(&binfmt_lock);
list_for_each_entry(fmt, &formats, lh) {
int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
if (!fn)
continue;
if (!try_module_get(fmt->module))
continue;
read_unlock(&binfmt_lock);
retval = fn(bprm, regs);
if (retval >= 0) {
tracehook_report_exec(fmt, bprm, regs);
put_binfmt(fmt);
allow_write_access(bprm->file);
if (bprm->file)
fput(bprm->file);
bprm->file = NULL;
current->did_exec = 1;
proc_exec_connector(current);
return retval;
}
read_lock(&binfmt_lock);
put_binfmt(fmt);
if (retval != -ENOEXEC || bprm->mm == NULL)
break;
if (!bprm->file) {
read_unlock(&binfmt_lock);
return retval;
}
}
read_unlock(&binfmt_lock);
if (retval != -ENOEXEC || bprm->mm == NULL) {
break;
#ifdef CONFIG_MODULES
} else {
#define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
if (printable(bprm->buf[0]) &&
printable(bprm->buf[1]) &&
printable(bprm->buf[2]) &&
printable(bprm->buf[3]))
break; /* -ENOEXEC */
request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
#endif
}
}
return retval;
}
EXPORT_SYMBOL(search_binary_handler);
void free_bprm(struct linux_binprm *bprm)
{
free_arg_pages(bprm);
kfree(bprm);
}
/*
* sys_execve() executes a new program.
*/
int do_execve(char * filename,
char __user *__user *argv,
char __user *__user *envp,
struct pt_regs * regs)
{
struct linux_binprm *bprm;
struct file *file;
struct files_struct *displaced;
int retval;
retval = unshare_files(&displaced);
if (retval)
goto out_ret;
retval = -ENOMEM;
bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
if (!bprm)
goto out_files;
file = open_exec(filename);
retval = PTR_ERR(file);
if (IS_ERR(file))
goto out_kfree;
sched_exec();
bprm->file = file;
bprm->filename = filename;
bprm->interp = filename;
retval = bprm_mm_init(bprm);
if (retval)
goto out_file;
bprm->argc = count(argv, MAX_ARG_STRINGS);
if ((retval = bprm->argc) < 0)
goto out_mm;
bprm->envc = count(envp, MAX_ARG_STRINGS);
if ((retval = bprm->envc) < 0)
goto out_mm;
retval = security_bprm_alloc(bprm);
if (retval)
goto out;
retval = prepare_binprm(bprm);
if (retval < 0)
goto out;
retval = copy_strings_kernel(1, &bprm->filename, bprm);
if (retval < 0)
goto out;
bprm->exec = bprm->p;
retval = copy_strings(bprm->envc, envp, bprm);
if (retval < 0)
goto out;
retval = copy_strings(bprm->argc, argv, bprm);
if (retval < 0)
goto out;
current->flags &= ~PF_KTHREAD;
retval = search_binary_handler(bprm,regs);
if (retval >= 0) {
/* execve success */
security_bprm_free(bprm);
acct_update_integrals(current);
free_bprm(bprm);
if (displaced)
put_files_struct(displaced);
return retval;
}
out:
if (bprm->security)
security_bprm_free(bprm);
out_mm:
if (bprm->mm)
mmput (bprm->mm);
out_file:
if (bprm->file) {
allow_write_access(bprm->file);
fput(bprm->file);
}
out_kfree:
free_bprm(bprm);
out_files:
if (displaced)
reset_files_struct(displaced);
out_ret:
return retval;
}
int set_binfmt(struct linux_binfmt *new)
{
struct linux_binfmt *old = current->binfmt;
if (new) {
if (!try_module_get(new->module))
return -1;
}
current->binfmt = new;
if (old)
module_put(old->module);
return 0;
}
EXPORT_SYMBOL(set_binfmt);
/* format_corename will inspect the pattern parameter, and output a
* name into corename, which must have space for at least
* CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
*/
static int format_corename(char *corename, long signr)
{
const struct cred *cred = current_cred();
const char *pat_ptr = core_pattern;
int ispipe = (*pat_ptr == '|');
char *out_ptr = corename;
char *const out_end = corename + CORENAME_MAX_SIZE;
int rc;
int pid_in_pattern = 0;
/* Repeat as long as we have more pattern to process and more output
space */
while (*pat_ptr) {
if (*pat_ptr != '%') {
if (out_ptr == out_end)
goto out;
*out_ptr++ = *pat_ptr++;
} else {
switch (*++pat_ptr) {
case 0:
goto out;
/* Double percent, output one percent */
case '%':
if (out_ptr == out_end)
goto out;
*out_ptr++ = '%';
break;
/* pid */
case 'p':
pid_in_pattern = 1;
rc = snprintf(out_ptr, out_end - out_ptr,
"%d", task_tgid_vnr(current));
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
break;
/* uid */
case 'u':
rc = snprintf(out_ptr, out_end - out_ptr,
"%d", cred->uid);
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
break;
/* gid */
case 'g':
rc = snprintf(out_ptr, out_end - out_ptr,
"%d", cred->gid);
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
break;
/* signal that caused the coredump */
case 's':
rc = snprintf(out_ptr, out_end - out_ptr,
"%ld", signr);
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
break;
/* UNIX time of coredump */
case 't': {
struct timeval tv;
do_gettimeofday(&tv);
rc = snprintf(out_ptr, out_end - out_ptr,
"%lu", tv.tv_sec);
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
break;
}
/* hostname */
case 'h':
down_read(&uts_sem);
rc = snprintf(out_ptr, out_end - out_ptr,
"%s", utsname()->nodename);
up_read(&uts_sem);
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
break;
/* executable */
case 'e':
rc = snprintf(out_ptr, out_end - out_ptr,
"%s", current->comm);
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
break;
/* core limit size */
case 'c':
rc = snprintf(out_ptr, out_end - out_ptr,
"%lu", current->signal->rlim[RLIMIT_CORE].rlim_cur);
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
break;
default:
break;
}
++pat_ptr;
}
}
/* Backward compatibility with core_uses_pid:
*
* If core_pattern does not include a %p (as is the default)
* and core_uses_pid is set, then .%pid will be appended to
* the filename. Do not do this for piped commands. */
if (!ispipe && !pid_in_pattern && core_uses_pid) {
rc = snprintf(out_ptr, out_end - out_ptr,
".%d", task_tgid_vnr(current));
if (rc > out_end - out_ptr)
goto out;
out_ptr += rc;
}
out:
*out_ptr = 0;
return ispipe;
}
static int zap_process(struct task_struct *start)
{
struct task_struct *t;
int nr = 0;
start->signal->flags = SIGNAL_GROUP_EXIT;
start->signal->group_stop_count = 0;
t = start;
do {
if (t != current && t->mm) {
sigaddset(&t->pending.signal, SIGKILL);
signal_wake_up(t, 1);
nr++;
}
} while_each_thread(start, t);
return nr;
}
static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
struct core_state *core_state, int exit_code)
{
struct task_struct *g, *p;
unsigned long flags;
int nr = -EAGAIN;
spin_lock_irq(&tsk->sighand->siglock);
if (!signal_group_exit(tsk->signal)) {
mm->core_state = core_state;
tsk->signal->group_exit_code = exit_code;
nr = zap_process(tsk);
}
spin_unlock_irq(&tsk->sighand->siglock);
if (unlikely(nr < 0))
return nr;
if (atomic_read(&mm->mm_users) == nr + 1)
goto done;
/*
* We should find and kill all tasks which use this mm, and we should
* count them correctly into ->nr_threads. We don't take tasklist
* lock, but this is safe wrt:
*
* fork:
* None of sub-threads can fork after zap_process(leader). All
* processes which were created before this point should be
* visible to zap_threads() because copy_process() adds the new
* process to the tail of init_task.tasks list, and lock/unlock
* of ->siglock provides a memory barrier.
*
* do_exit:
* The caller holds mm->mmap_sem. This means that the task which
* uses this mm can't pass exit_mm(), so it can't exit or clear
* its ->mm.
*
* de_thread:
* It does list_replace_rcu(&leader->tasks, &current->tasks),
* we must see either old or new leader, this does not matter.
* However, it can change p->sighand, so lock_task_sighand(p)
* must be used. Since p->mm != NULL and we hold ->mmap_sem
* it can't fail.
*
* Note also that "g" can be the old leader with ->mm == NULL
* and already unhashed and thus removed from ->thread_group.
* This is OK, __unhash_process()->list_del_rcu() does not
* clear the ->next pointer, we will find the new leader via
* next_thread().
*/
rcu_read_lock();
for_each_process(g) {
if (g == tsk->group_leader)
continue;
if (g->flags & PF_KTHREAD)
continue;
p = g;
do {
if (p->mm) {
if (unlikely(p->mm == mm)) {
lock_task_sighand(p, &flags);
nr += zap_process(p);
unlock_task_sighand(p, &flags);
}
break;
}
} while_each_thread(g, p);
}
rcu_read_unlock();
done:
atomic_set(&core_state->nr_threads, nr);
return nr;
}
static int coredump_wait(int exit_code, struct core_state *core_state)
{
struct task_struct *tsk = current;
struct mm_struct *mm = tsk->mm;
struct completion *vfork_done;
int core_waiters;
init_completion(&core_state->startup);
core_state->dumper.task = tsk;
core_state->dumper.next = NULL;
core_waiters = zap_threads(tsk, mm, core_state, exit_code);
up_write(&mm->mmap_sem);
if (unlikely(core_waiters < 0))
goto fail;
/*
* Make sure nobody is waiting for us to release the VM,
* otherwise we can deadlock when we wait on each other
*/
vfork_done = tsk->vfork_done;
if (vfork_done) {
tsk->vfork_done = NULL;
complete(vfork_done);
}
if (core_waiters)
wait_for_completion(&core_state->startup);
fail:
return core_waiters;
}
static void coredump_finish(struct mm_struct *mm)
{
struct core_thread *curr, *next;
struct task_struct *task;
next = mm->core_state->dumper.next;
while ((curr = next) != NULL) {
next = curr->next;
task = curr->task;
/*
* see exit_mm(), curr->task must not see
* ->task == NULL before we read ->next.
*/
smp_mb();
curr->task = NULL;
wake_up_process(task);
}
mm->core_state = NULL;
}
/*
* set_dumpable converts traditional three-value dumpable to two flags and
* stores them into mm->flags. It modifies lower two bits of mm->flags, but
* these bits are not changed atomically. So get_dumpable can observe the
* intermediate state. To avoid doing unexpected behavior, get get_dumpable
* return either old dumpable or new one by paying attention to the order of
* modifying the bits.
*
* dumpable | mm->flags (binary)
* old new | initial interim final
* ---------+-----------------------
* 0 1 | 00 01 01
* 0 2 | 00 10(*) 11
* 1 0 | 01 00 00
* 1 2 | 01 11 11
* 2 0 | 11 10(*) 00
* 2 1 | 11 11 01
*
* (*) get_dumpable regards interim value of 10 as 11.
*/
void set_dumpable(struct mm_struct *mm, int value)
{
switch (value) {
case 0:
clear_bit(MMF_DUMPABLE, &mm->flags);
smp_wmb();
clear_bit(MMF_DUMP_SECURELY, &mm->flags);
break;
case 1:
set_bit(MMF_DUMPABLE, &mm->flags);
smp_wmb();
clear_bit(MMF_DUMP_SECURELY, &mm->flags);
break;
case 2:
set_bit(MMF_DUMP_SECURELY, &mm->flags);
smp_wmb();
set_bit(MMF_DUMPABLE, &mm->flags);
break;
}
}
int get_dumpable(struct mm_struct *mm)
{
int ret;
ret = mm->flags & 0x3;
return (ret >= 2) ? 2 : ret;
}
int do_coredump(long signr, int exit_code, struct pt_regs * regs)
{
struct core_state core_state;
char corename[CORENAME_MAX_SIZE + 1];
struct mm_struct *mm = current->mm;
struct linux_binfmt * binfmt;
struct inode * inode;
struct file * file;
const struct cred *old_cred;
struct cred *cred;
int retval = 0;
int flag = 0;
int ispipe = 0;
unsigned long core_limit = current->signal->rlim[RLIMIT_CORE].rlim_cur;
char **helper_argv = NULL;
int helper_argc = 0;
char *delimit;
audit_core_dumps(signr);
binfmt = current->binfmt;
if (!binfmt || !binfmt->core_dump)
goto fail;
cred = prepare_creds();
if (!cred) {
retval = -ENOMEM;
goto fail;
}
down_write(&mm->mmap_sem);
/*
* If another thread got here first, or we are not dumpable, bail out.
*/
if (mm->core_state || !get_dumpable(mm)) {
up_write(&mm->mmap_sem);
put_cred(cred);
goto fail;
}
/*
* We cannot trust fsuid as being the "true" uid of the
* process nor do we know its entire history. We only know it
* was tainted so we dump it as root in mode 2.
*/
if (get_dumpable(mm) == 2) { /* Setuid core dump mode */
flag = O_EXCL; /* Stop rewrite attacks */
cred->fsuid = 0; /* Dump root private */
}
retval = coredump_wait(exit_code, &core_state);
if (retval < 0) {
put_cred(cred);
goto fail;
}
old_cred = override_creds(cred);
/*
* Clear any false indication of pending signals that might
* be seen by the filesystem code called to write the core file.
*/
clear_thread_flag(TIF_SIGPENDING);
/*
* lock_kernel() because format_corename() is controlled by sysctl, which
* uses lock_kernel()
*/
lock_kernel();
ispipe = format_corename(corename, signr);
unlock_kernel();
/*
* Don't bother to check the RLIMIT_CORE value if core_pattern points
* to a pipe. Since we're not writing directly to the filesystem
* RLIMIT_CORE doesn't really apply, as no actual core file will be
* created unless the pipe reader choses to write out the core file
* at which point file size limits and permissions will be imposed
* as it does with any other process
*/
if ((!ispipe) && (core_limit < binfmt->min_coredump))
goto fail_unlock;
if (ispipe) {
helper_argv = argv_split(GFP_KERNEL, corename+1, &helper_argc);
/* Terminate the string before the first option */
delimit = strchr(corename, ' ');
if (delimit)
*delimit = '\0';
delimit = strrchr(helper_argv[0], '/');
if (delimit)
delimit++;
else
delimit = helper_argv[0];
if (!strcmp(delimit, current->comm)) {
printk(KERN_NOTICE "Recursive core dump detected, "
"aborting\n");
goto fail_unlock;
}
core_limit = RLIM_INFINITY;
/* SIGPIPE can happen, but it's just never processed */
if (call_usermodehelper_pipe(corename+1, helper_argv, NULL,
&file)) {
printk(KERN_INFO "Core dump to %s pipe failed\n",
corename);
goto fail_unlock;
}
} else
file = filp_open(corename,
O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
0600);
if (IS_ERR(file))
goto fail_unlock;
inode = file->f_path.dentry->d_inode;
if (inode->i_nlink > 1)
goto close_fail; /* multiple links - don't dump */
if (!ispipe && d_unhashed(file->f_path.dentry))
goto close_fail;
/* AK: actually i see no reason to not allow this for named pipes etc.,
but keep the previous behaviour for now. */
if (!ispipe && !S_ISREG(inode->i_mode))
goto close_fail;
/*
* Dont allow local users get cute and trick others to coredump
* into their pre-created files:
*/
if (inode->i_uid != current_fsuid())
goto close_fail;
if (!file->f_op)
goto close_fail;
if (!file->f_op->write)
goto close_fail;
if (!ispipe && do_truncate(file->f_path.dentry, 0, 0, file) != 0)
goto close_fail;
retval = binfmt->core_dump(signr, regs, file, core_limit);
if (retval)
current->signal->group_exit_code |= 0x80;
close_fail:
filp_close(file, NULL);
fail_unlock:
if (helper_argv)
argv_free(helper_argv);
revert_creds(old_cred);
put_cred(cred);
coredump_finish(mm);
fail:
return retval;
}