From 59ee6bf2ab6aa829b69b747a23a63bea72cd8d54 Mon Sep 17 00:00:00 2001
From: Vladislav Efanov <VEfanov@ispras.ru>
Date: Tue, 30 May 2023 14:39:41 +0300
Subject: [PATCH 4/4] udp6: Fix race condition in udp6_sendmsg & connect
Git-commit: 448a5ce1120c5bdbce1f1ccdabcd31c7d029f328
Patch-mainline: v6.4-rc5
References: git-fixes
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@ispras.ru>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Denis Kirjanov <denis.kirjanov@suse.com>
---
net/core/sock.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/core/sock.c b/net/core/sock.c
index 81c8909d2dd9..8ae2e6bd38bd 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1693,7 +1693,6 @@ 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;
if (sk->sk_route_caps & NETIF_F_GSO)
sk->sk_route_caps |= NETIF_F_GSO_SOFTWARE;
@@ -1708,6 +1707,7 @@ 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);
--
2.16.4