net/x25: Fix null-ptr-deref caused by x25_disconnect
[ Upstream commit 7781607938c8371d4c2b243527430241c62e39c2 ]
When the link layer is terminating, x25->neighbour will be set to NULL
in x25_disconnect(). As a result, it could cause null-ptr-deref bugs in
x25_sendmsg(),x25_recvmsg() and x25_connect(). One of the bugs is
shown below.
(Thread 1) | (Thread 2)
x25_link_terminated() | x25_recvmsg()
x25_kill_by_neigh() | ...
x25_disconnect() | lock_sock(sk)
... | ...
x25->neighbour = NULL //(1) |
... | x25->neighbour->extended //(2)
The code sets NULL to x25->neighbour in position (1) and dereferences
x25->neighbour in position (2), which could cause null-ptr-deref bug.
This patch adds lock_sock() in x25_kill_by_neigh() in order to synchronize
with x25_sendmsg(), x25_recvmsg() and x25_connect(). What`s more, the
sock held by lock_sock() is not NULL, because it is extracted from x25_list
and uses x25_list_lock to synchronize.
BUG=b/233870221
TEST=http://sponge2/344c0d46-9743-4275-8853-f04312939664
RELEASE_NOTE=Fixed CVE-2022-1516 in Linux Kernel
SOURCE=UPSTREAM(7781607938c8371d4c2b243527430241c62e39c2)
cos-patch: security-moderate
Fixes: 4becb7ee5b3d ("net/x25: Fix x25_neigh refcnt leak when x25 disconnect")
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
Reviewed-by: Lin Ma <linma@zju.edu.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Change-Id: I86c41503e48152fa742e4e856177ff197336644e
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/33301
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Vaibhav Rustagi <vaibhavrustagi@google.com>
diff --git a/net/x25/af_x25.c b/net/x25/af_x25.c
index d8d603a..c94aa58 100644
--- a/net/x25/af_x25.c
+++ b/net/x25/af_x25.c
@@ -1767,10 +1767,15 @@
write_lock_bh(&x25_list_lock);
- sk_for_each(s, &x25_list)
- if (x25_sk(s)->neighbour == nb)
+ sk_for_each(s, &x25_list) {
+ if (x25_sk(s)->neighbour == nb) {
+ write_unlock_bh(&x25_list_lock);
+ lock_sock(s);
x25_disconnect(s, ENETUNREACH, 0, 0);
-
+ release_sock(s);
+ write_lock_bh(&x25_list_lock);
+ }
+ }
write_unlock_bh(&x25_list_lock);
/* Remove any related forwards */
