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Message-Id: <20230530113941.1674072-1-VEfanov@ispras.ru> Date: Tue, 30 May 2023 14:39:41 +0300 From: Vladislav Efanov <VEfanov@...ras.ru> To: Willem de Bruijn <willemdebruijn.kernel@...il.com> Cc: Vladislav Efanov <VEfanov@...ras.ru>, "David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org Subject: [PATCH v2] udp6: Fix race condition in udp6_sendmsg & connect 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@...ras.ru> Signed-off-by: Paolo Abeni <pabeni@...hat.com> --- v2: Move sk_dst_set() call in sk_setup_caps() as Paolo Abeni <pabeni@...hat.com> suggested. 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 5440e67bcfe3..24f2761bdb1d 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -2381,7 +2381,6 @@ 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_is_tcp(sk)) sk->sk_route_caps |= NETIF_F_GSO; @@ -2400,6 +2399,7 @@ 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); -- 2.34.1
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