net/smc: do not dereference an unset send buffer on the SMC-D teardown path

smc_close_stream_wait() calls smc_tx_prepared_sends() from inside its
sk_wait_event() condition, and sk_wait_event() evaluates that condition
once with the socket lock released. smcd_buf_detach() clears
conn->sndbuf_desc from smc_conn_kill() under lock_sock(), so a link group
terminating while a socket waits there leaves the helper dereferencing
NULL, faulting out of close(). SIOCOUTQ reads the field by hand, and
smc_close_cancel_work() drops the lock across two cancel_*_sync() calls.

Sample the pointer once in the helper, report nothing prepared while it is
unset, and bound the ioctl the same way. The receive tasklet dereferences
the field directly in smc_cdc_msg_recv_action(), not through this helper;
1/2 is what keeps it from running that late.

Fixes: ae2be35cbed2 ("net/smc: {at|de}tach sndbuf to peer DMB if supported")
Cc: stable@vger.kernel.org
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Reviewed-by: Sidraya Jayagond <sidraya@linux.ibm.com>
Reviewed-by: Tony Lu <tonylu@linux.alibaba.com>
Link: https://patch.msgid.link/20260808-b4-disp-22f119e6-v2-2-61647601a6f3@proton.me
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

0 files changed, 0 insertions, 0 deletions