This is a note to let you know that I've just added the patch titled tipc: increment the tmp aead refcnt before attaching it to the 5.11-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: tipc-increment-the-tmp-aead-refcnt-before-attaching-.patch and it can be found in the queue-5.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 549c289fb413b4fa538903dd53d0b329b2b6f480 Author: Xin Long <lucien.xin@xxxxxxxxx> Date: Tue Apr 6 10:45:23 2021 +0800 tipc: increment the tmp aead refcnt before attaching it [ Upstream commit 2a2403ca3add03f542f6b34bef9f74649969b06d ] Li Shuang found a NULL pointer dereference crash in her testing: [] BUG: unable to handle kernel NULL pointer dereference at 0000000000000020 [] RIP: 0010:tipc_crypto_rcv_complete+0xc8/0x7e0 [tipc] [] Call Trace: [] <IRQ> [] tipc_crypto_rcv+0x2d9/0x8f0 [tipc] [] tipc_rcv+0x2fc/0x1120 [tipc] [] tipc_udp_recv+0xc6/0x1e0 [tipc] [] udpv6_queue_rcv_one_skb+0x16a/0x460 [] udp6_unicast_rcv_skb.isra.35+0x41/0xa0 [] ip6_protocol_deliver_rcu+0x23b/0x4c0 [] ip6_input+0x3d/0xb0 [] ipv6_rcv+0x395/0x510 [] __netif_receive_skb_core+0x5fc/0xc40 This is caused by NULL returned by tipc_aead_get(), and then crashed when dereferencing it later in tipc_crypto_rcv_complete(). This might happen when tipc_crypto_rcv_complete() is called by two threads at the same time: the tmp attached by tipc_crypto_key_attach() in one thread may be released by the one attached by that in the other thread. This patch is to fix it by incrementing the tmp's refcnt before attaching it instead of calling tipc_aead_get() after attaching it. Fixes: fc1b6d6de220 ("tipc: introduce TIPC encryption & authentication") Reported-by: Li Shuang <shuali@xxxxxxxxxx> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c index f4fca8f7f63f..97710ce36047 100644 --- a/net/tipc/crypto.c +++ b/net/tipc/crypto.c @@ -1941,12 +1941,13 @@ static void tipc_crypto_rcv_complete(struct net *net, struct tipc_aead *aead, goto rcv; if (tipc_aead_clone(&tmp, aead) < 0) goto rcv; + WARN_ON(!refcount_inc_not_zero(&tmp->refcnt)); if (tipc_crypto_key_attach(rx, tmp, ehdr->tx_key, false) < 0) { tipc_aead_free(&tmp->rcu); goto rcv; } tipc_aead_put(aead); - aead = tipc_aead_get(tmp); + aead = tmp; } if (unlikely(err)) {