sctp: check RCV_SHUTDOWN after the sendmsg connect wait

sctp_wait_for_connect() drops the socket lock while it sleeps. An
out-of-the-blue ABORT can then be processed from the socket backlog and
unlink the association. If a concurrent shutdown(fd, SHUT_RD) sets
RCV_SHUTDOWN, the waiter breaks with err == 0 before checking
asoc->base.dead. Its final sctp_association_put() can then free the
association, leaving sctp_sendmsg_to_asoc() to continue with a dangling
pointer.

Check RCV_SHUTDOWN along with the wait error in sctp_sendmsg_to_asoc()
before using the association again. The check only accesses the socket,
so it needs no additional association reference. Return the existing
-ESRCH so that sctp_sendmsg() skips freeing a new association that may
already have been destroyed.

Keep sctp_wait_for_connect() unchanged to preserve its behavior for the
connect() caller.

Fixes: 668c9beb9020 ("sctp: implement assign_number for sctp_stream_interleave")
Cc: stable@vger.kernel.org
Reported-by: TencentOS Corvus AI <corvus@tencent.com>
Signed-off-by: Jun Yang <junvyyang@tencent.com>
Acked-by: Xin Long <lucien.xin@gmail.com>
Link: https://patch.msgid.link/20260926095606.68601-1-juny24602@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions