[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>

1 files changed, 12 insertions, 0 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index d891883420f7..4b6fb054b25d 100644
--- a/kernel/exit.c
+++ b/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;