This is a note to let you know that I've just added the patch titled
udp6: Fix race condition in udp6_sendmsg & connect
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
udp6-fix-race-condition-in-udp6_sendmsg-connect.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit dbabad4b8220ab847dc95ba5924f880a5722b7a8
Author: Vladislav Efanov <VEfanov@xxxxxxxxx>
Date: Tue May 30 14:39:41 2023 +0300
udp6: Fix race condition in udp6_sendmsg & connect
[ Upstream commit 448a5ce1120c5bdbce1f1ccdabcd31c7d029f328 ]
Syzkaller got the following report:
BUG: KASAN: use-after-free in sk_setup_caps+0x621/0x690 net/core/sock.c:2018
Read of size 8 at addr ffff888027f82780 by task syz-executor276/3255
The function sk_setup_caps (called by ip6_sk_dst_store_flow->
ip6_dst_store) referenced already freed memory as this memory was
freed by parallel task in udpv6_sendmsg->ip6_sk_dst_lookup_flow->
sk_dst_check.
task1 (connect) task2 (udp6_sendmsg)
sk_setup_caps->sk_dst_set |
| sk_dst_check->
| sk_dst_set
| dst_release
sk_setup_caps references |
to already freed dst_entry|
The reason for this race condition is: sk_setup_caps() keeps using
the dst after transferring the ownership to the dst cache.
Found by Linux Verification Center (linuxtesting.org) with syzkaller.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Vladislav Efanov <VEfanov@xxxxxxxxx>
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/core/sock.c b/net/core/sock.c
index cd23a8e4556ca..347a55519d0a5 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1795,7 +1795,6 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst)
{
u32 max_segs = 1;
- sk_dst_set(sk, dst);
sk->sk_route_caps = dst->dev->features | sk->sk_route_forced_caps;
if (sk->sk_route_caps & NETIF_F_GSO)
sk->sk_route_caps |= NETIF_F_GSO_SOFTWARE;
@@ -1810,6 +1809,7 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst)
}
}
sk->sk_gso_max_segs = max_segs;
+ sk_dst_set(sk, dst);
}
EXPORT_SYMBOL_GPL(sk_setup_caps);
