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* [PATCH net-next] tipc: fix an use-after-free issue in tipc_recvmsg
@ 2021-07-23 17:25 Xin Long
  2021-07-25  9:50 ` patchwork-bot+netdevbpf
  0 siblings, 1 reply; 2+ messages in thread
From: Xin Long @ 2021-07-23 17:25 UTC (permalink / raw)
  To: network dev, davem, kuba, Jon Maloy, tipc-discussion; +Cc: Hoang Huu Le

syzbot reported an use-after-free crash:

  BUG: KASAN: use-after-free in tipc_recvmsg+0xf77/0xf90 net/tipc/socket.c:1979
  Call Trace:
   tipc_recvmsg+0xf77/0xf90 net/tipc/socket.c:1979
   sock_recvmsg_nosec net/socket.c:943 [inline]
   sock_recvmsg net/socket.c:961 [inline]
   sock_recvmsg+0xca/0x110 net/socket.c:957
   tipc_conn_rcv_from_sock+0x162/0x2f0 net/tipc/topsrv.c:398
   tipc_conn_recv_work+0xeb/0x190 net/tipc/topsrv.c:421
   process_one_work+0x98d/0x1630 kernel/workqueue.c:2276
   worker_thread+0x658/0x11f0 kernel/workqueue.c:2422

As Hoang pointed out, it was caused by skb_cb->bytes_read still accessed
after calling tsk_advance_rx_queue() to free the skb in tipc_recvmsg().

This patch is to fix it by accessing skb_cb->bytes_read earlier than
calling tsk_advance_rx_queue().

Fixes: f4919ff59c28 ("tipc: keep the skb in rcv queue until the whole data is read")
Signed-off-by: Xin Long <>
Acked-by: Jon Maloy <>
 net/tipc/socket.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index 9b0b311c7ec1..b0dd183a4dbc 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -1973,10 +1973,12 @@ static int tipc_recvmsg(struct socket *sock, struct msghdr *m,
 		tipc_node_distr_xmit(sock_net(sk), &xmitq);
-	if (!skb_cb->bytes_read)
-		tsk_advance_rx_queue(sk);
+	if (skb_cb->bytes_read)
+		goto exit;
+	tsk_advance_rx_queue(sk);
-	if (likely(!connected) || skb_cb->bytes_read)
+	if (likely(!connected))
 		goto exit;
 	/* Send connection flow control advertisement when applicable */

^ permalink raw reply	[flat|nested] 2+ messages in thread

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2021-07-23 17:25 [PATCH net-next] tipc: fix an use-after-free issue in tipc_recvmsg Xin Long
2021-07-25  9:50 ` patchwork-bot+netdevbpf

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