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>
---
net/sctp/socket.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index b91616f819de..218e0982c370 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1830,6 +1830,10 @@ 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)) {
--
2.39.1
