This is a note to let you know that I've just added the patch titled
sctp: check send stream number after wait_for_sndbuf
to the 4.19-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:
sctp-check-send-stream-number-after-wait_for_sndbuf.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit b958f515b75451e4b7259700f46d49b38ddbab32
Author: Xin Long <lucien.xin@xxxxxxxxx>
Date: Sat Apr 1 19:09:57 2023 -0400
sctp: check send stream number after wait_for_sndbuf
[ Upstream commit 2584024b23552c00d95b50255e47bd18d306d31a ]
This patch fixes a corner case where the asoc out stream count may change
after wait_for_sndbuf.
When the main thread in the client starts a connection, if its out stream
count is set to N while the in stream count in the server is set to N - 2,
another thread in the client keeps sending the msgs with stream number
N - 1, and waits for sndbuf before processing INIT_ACK.
However, after processing INIT_ACK, the out stream count in the client is
shrunk to N - 2, the same to the in stream count in the server. The crash
occurs when the thread waiting for sndbuf is awake and sends the msg in a
non-existing stream(N - 1), the call trace is as below:
KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]
Call Trace:
<TASK>
sctp_cmd_send_msg net/sctp/sm_sideeffect.c:1114 [inline]
sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1777 [inline]
sctp_side_effects net/sctp/sm_sideeffect.c:1199 [inline]
sctp_do_sm+0x197d/0x5310 net/sctp/sm_sideeffect.c:1170
sctp_primitive_SEND+0x9f/0xc0 net/sctp/primitive.c:163
sctp_sendmsg_to_asoc+0x10eb/0x1a30 net/sctp/socket.c:1868
sctp_sendmsg+0x8d4/0x1d90 net/sctp/socket.c:2026
inet_sendmsg+0x9d/0xe0 net/ipv4/af_inet.c:825
sock_sendmsg_nosec net/socket.c:722 [inline]
sock_sendmsg+0xde/0x190 net/socket.c:745
The fix is to add an unlikely check for the send stream number after the
thread wakes up from the wait_for_sndbuf.
Fixes: 5bbbbe32a431 ("sctp: introduce stream scheduler foundations")
Reported-by: syzbot+47c24ca20a2fa01f082e@xxxxxxxxxxxxxxxxxxxxxxxxx
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/sctp/socket.c b/net/sctp/socket.c
index 8901bb7afa2be..355b89579e930 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1953,6 +1953,10 @@ static int sctp_sendmsg_to_asoc(struct sctp_association *asoc,
err = sctp_wait_for_sndbuf(asoc, &timeo, msg_len);
if (err)
goto err;
+ if (unlikely(sinfo->sinfo_stream >= asoc->stream.outcnt)) {
+ err = -EINVAL;
+ goto err;
+ }
}
if (sctp_state(asoc, CLOSED)) {
