Commit 3b9b8ab6 authored by Kirill Korotaev's avatar Kirill Korotaev Committed by Linus Torvalds

[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: default avatarPavel Emelianov <xemul@openvz.org>
Signed-off-by: default avatarKirill Korotaev <dev@openvz.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent fc09561d
......@@ -1038,10 +1038,8 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
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;
......
......@@ -215,10 +215,8 @@ static int load_misc_binary(struct linux_binprm *bprm, struct pt_regs *regs)
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;
}
......
......@@ -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;
}
......
......@@ -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 */
......@@ -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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