From 8379bb84be757d5df2d818509faec5d66adb861d Mon Sep 17 00:00:00 2001 From: David Howells Date: Tue, 14 Jan 2020 16:06:14 +0000 Subject: [PATCH] keys: Fix request_key() cache When the key cached by request_key() and co. is cleaned up on exit(), the code looks in the wrong task_struct, and so clears the wrong cache. This leads to anomalies in key refcounting when doing, say, a kernel build on an afs volume, that then trigger kasan to report a use-after-free when the key is viewed in /proc/keys. Fix this by making exit_creds() look in the passed-in task_struct rather than in current (the task_struct cleanup code is deferred by RCU and potentially run in another task). Fixes: 7743c48e54ee ("keys: Cache result of request_key*() temporarily in task_struct") Signed-off-by: David Howells Signed-off-by: Linus Torvalds --- kernel/cred.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/cred.c b/kernel/cred.c index c0a4c12d38b2..56395be1c2a8 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -175,8 +175,8 @@ void exit_creds(struct task_struct *tsk) put_cred(cred); #ifdef CONFIG_KEYS_REQUEST_CACHE - key_put(current->cached_requested_key); - current->cached_requested_key = NULL; + key_put(tsk->cached_requested_key); + tsk->cached_requested_key = NULL; #endif }