From: Vladislav Efanov VEfanov@ispras.ru
[ 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@ispras.ru Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- 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 7f6f1a0bf8a13..5e1dccbd61a60 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1938,7 +1938,6 @@ 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; @@ -1953,6 +1952,7 @@ 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);