[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Message-Id: <20240815084907.167870-1-sunyiqixm@gmail.com>
Date: Thu, 15 Aug 2024 16:49:07 +0800
From: sunyiqi <sunyiqixm@...il.com>
To: davem@...emloft.net,
edumazet@...gle.com,
kuba@...nel.org,
pabeni@...hat.com
Cc: netdev@...r.kernel.org,
linux-kernel@...r.kernel.org,
sunyiqi <sunyiqixm@...il.com>
Subject: [PATCH] net: do not release sk in sk_wait_event
When investigating the kcm socket UAF which is also found by syzbot,
I found that the root cause of this problem is actually in
sk_wait_event.
In sk_wait_event, sk is released and relocked and called by
sk_stream_wait_memory. Protocols like tcp, kcm, etc., called it in some
ops function like *sendmsg which will lock the sk at the beginning.
But sk_stream_wait_memory releases sk unexpectedly and destroy
the thread safety. Finally it causes the kcm sk UAF.
If at the time when a thread(thread A) calls sk_stream_wait_memory
and the other thread(thread B) is waiting for lock in lock_sock,
thread B will successfully get the sk lock as thread A release sk lock
in sk_wait_event.
The thread B may change the sk which is not thread A expecting.
As a result, it will lead kernel to the unexpected behavior. Just like
the kcm sk UAF, which is actually cause by sk_wait_event in
sk_stream_wait_memory.
Previous commit d9dc8b0f8b4e ("net: fix sleeping for sk_wait_event()")
in 2016 seems do not solved this problem. Is it necessary to release
sock in sk_wait_event? Or just delete it to make the protocol ops
thread-secure.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Link: https://syzkaller.appspot.com/bug?extid=b72d86aa5df17ce74c60
Signed-off-by: sunyiqi <sunyiqixm@...il.com>
---
include/net/sock.h | 2 --
1 file changed, 2 deletions(-)
diff --git a/include/net/sock.h b/include/net/sock.h
index cce23ac4d514..08d3b204b019 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1145,7 +1145,6 @@ static inline void sock_rps_reset_rxhash(struct sock *sk)
#define sk_wait_event(__sk, __timeo, __condition, __wait) \
({ int __rc, __dis = __sk->sk_disconnects; \
- release_sock(__sk); \
__rc = __condition; \
if (!__rc) { \
*(__timeo) = wait_woken(__wait, \
@@ -1153,7 +1152,6 @@ static inline void sock_rps_reset_rxhash(struct sock *sk)
*(__timeo)); \
} \
sched_annotate_sleep(); \
- lock_sock(__sk); \
__rc = __dis == __sk->sk_disconnects ? __condition : -EPIPE; \
__rc; \
})
--
2.34.1
Powered by blists - more mailing lists