exec: Copy oldsighand->action under spin-lock

unshare_sighand should only access oldsighand->action
while holding oldsighand->siglock, to make sure that
newsighand->action is in a consistent state.

Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Cc: stable@vger.kernel.org
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/AM8PR10MB470871DEBD1DED081F9CC391E4389@AM8PR10MB4708.EURPRD10.PROD.OUTLOOK.COM

diff --git a/fs/exec.c b/fs/exec.c
index 349a5da..32dc8cf 100644 (file)
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1197,11 +1197,11 @@ static int unshare_sighand(struct task_struct *me)
                        return -ENOMEM;
 
                refcount_set(&newsighand->count, 1);
-               memcpy(newsighand->action, oldsighand->action,
-                      sizeof(newsighand->action));
 
                write_lock_irq(&tasklist_lock);
                spin_lock(&oldsighand->siglock);
+               memcpy(newsighand->action, oldsighand->action,
+                      sizeof(newsighand->action));
                rcu_assign_pointer(me->sighand, newsighand);
                spin_unlock(&oldsighand->siglock);
                write_unlock_irq(&tasklist_lock);