[PATCH 5.15 056/120] tipc: re-fetch skb cb after tipc_msg_validate

Greg Kroah-Hartman
2022-12-05T19:38:38Z

From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit 3067bc61fcfe3081bf4807ce65560f499e895e77 ]

As the call trace shows, the original skb was freed in tipc_msg_validate(),
and dereferencing the old skb cb would cause an use-after-free crash.

BUG: KASAN: use-after-free in tipc_crypto_rcv_complete+0x1835/0x2240 [tipc]
Call Trace:
<IRQ>
tipc_crypto_rcv_complete+0x1835/0x2240 [tipc]
tipc_crypto_rcv+0xd32/0x1ec0 [tipc]
tipc_rcv+0x744/0x1150 [tipc]
...
Allocated by task 47078:
kmem_cache_alloc_node+0x158/0x4d0
__alloc_skb+0x1c1/0x270
tipc_buf_acquire+0x1e/0xe0 [tipc]
tipc_msg_create+0x33/0x1c0 [tipc]
tipc_link_build_proto_msg+0x38a/0x2100 [tipc]
tipc_link_timeout+0x8b8/0xef0 [tipc]
tipc_node_timeout+0x2a1/0x960 [tipc]
call_timer_fn+0x2d/0x1c0
...
Freed by task 47078:
tipc_msg_validate+0x7b/0x440 [tipc]
tipc_crypto_rcv_complete+0x4b5/0x2240 [tipc]
tipc_crypto_rcv+0xd32/0x1ec0 [tipc]
tipc_rcv+0x744/0x1150 [tipc]

This patch fixes it by re-fetching the skb cb from the new allocated skb
after calling tipc_msg_validate().

Fixes: fc1b6d6de220 ("tipc: introduce TIPC encryption & authentication")
Reported-by: Shuang Li <shuali@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Link: https://lore.kernel.org/r/1b1cdba762915325bd8ef9a98d0276eb673df2a5.1669398403.git.lucien.xin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/tipc/crypto.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/net/tipc/crypto.c b/net/tipc/crypto.c
index b5074957e881..4243d2ab8adf 100644
--- a/net/tipc/crypto.c
+++ b/net/tipc/crypto.c
@@ -1982,6 +1982,9 @@ static void tipc_crypto_rcv_complete(struct net *net, struct tipc_aead *aead,
/* Ok, everything's fine, try to synch own keys according to peers' */
tipc_crypto_key_synch(rx, *skb);

+ /* Re-fetch skb cb as skb might be changed in tipc_msg_validate */
+ skb_cb = TIPC_SKB_CB(*skb);
+
/* Mark skb decrypted */
skb_cb->decrypted = 1;

--
2.35.1