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[PATCH] Fix unserialized task->files changing

Fixed race on put_files_struct on exec with proc.  Restoring files on
current on error path may lead to proc having a pointer to already kfree-d
files_struct.

->files changing at exit.c and khtread.c are safe as exit_files() makes all
things under lock.

Found during OpenVZ stress testing.

[akpm@osdl.org: add export]
Signed-off-by: Pavel Emelianov <xemul@openvz.org>
Signed-off-by: Kirill Korotaev <dev@openvz.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
master
Kirill Korotaev 15 years ago
committed by Linus Torvalds
parent
commit
3b9b8ab65d
  1. 6
      fs/binfmt_elf.c
  2. 6
      fs/binfmt_misc.c
  3. 3
      fs/exec.c
  4. 1
      include/linux/file.h
  5. 12
      kernel/exit.c

6
fs/binfmt_elf.c

@ -1038,10 +1038,8 @@ out_free_interp:
out_free_file:
sys_close(elf_exec_fileno);
out_free_fh:
if (files) {
put_files_struct(current->files);
current->files = files;
}
if (files)
reset_files_struct(current, files);
out_free_ph:
kfree(elf_phdata);
goto out;

6
fs/binfmt_misc.c

@ -215,10 +215,8 @@ _error:
bprm->interp_flags = 0;
bprm->interp_data = 0;
_unshare:
if (files) {
put_files_struct(current->files);
current->files = files;
}
if (files)
reset_files_struct(current, files);
goto _ret;
}

3
fs/exec.c

@ -898,8 +898,7 @@ int flush_old_exec(struct linux_binprm * bprm)
return 0;
mmap_failed:
put_files_struct(current->files);
current->files = files;
reset_files_struct(current, files);
out:
return retval;
}

1
include/linux/file.h

@ -112,5 +112,6 @@ struct task_struct;
struct files_struct *get_files_struct(struct task_struct *);
void FASTCALL(put_files_struct(struct files_struct *fs));
void reset_files_struct(struct task_struct *, struct files_struct *);
#endif /* __LINUX_FILE_H */

12
kernel/exit.c

@ -487,6 +487,18 @@ void fastcall put_files_struct(struct files_struct *files)
EXPORT_SYMBOL(put_files_struct);
void reset_files_struct(struct task_struct *tsk, struct files_struct *files)
{
struct files_struct *old;
old = tsk->files;
task_lock(tsk);
tsk->files = files;
task_unlock(tsk);
put_files_struct(old);
}
EXPORT_SYMBOL(reset_files_struct);
static inline void __exit_files(struct task_struct *tsk)
{
struct files_struct * files = tsk->files;

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