On Friday, July 23, 2021, 12:40:22 PM EDT, Xin Long <lucien....@gmail.com>
wrote:
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")
Reported-by: syzbot+e6741b97d5552f97c...@syzkaller.appspotmail.com
Signed-off-by: Xin Long <lucien....@gmail.com>
---
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 */
--
2.27.0
For some reason this one did not show up in my RH mailbox.Anyway,Acked-by: Jon
Maloy <jma...@redhat.com>
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