From b395dd319cea422239cb45b998fb38d7e373af87 Mon Sep 17 00:00:00 2001 From: Bryam Vargas Date: Sat, 8 Aug 2026 02:21:24 -0500 Subject: [PATCH] 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 Reviewed-by: Sidraya Jayagond Reviewed-by: Tony Lu Link: https://patch.msgid.link/20260808-b4-disp-22f119e6-v2-2-61647601a6f3@proton.me Signed-off-by: Jakub Kicinski --- net/smc/af_smc.c | 3 ++- net/smc/smc_tx.h | 6 +++++- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index 00403175b740..cff910cedbfc 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -3233,7 +3233,8 @@ int smc_ioctl(struct socket *sock, unsigned int cmd, return -EINVAL; } if (smc->sk.sk_state == SMC_INIT || - smc->sk.sk_state == SMC_CLOSED) + smc->sk.sk_state == SMC_CLOSED || + !READ_ONCE(smc->conn.sndbuf_desc)) answ = 0; else answ = smc->conn.sndbuf_desc->len - diff --git a/net/smc/smc_tx.h b/net/smc/smc_tx.h index a59f370b8b43..610a945aefd6 100644 --- a/net/smc/smc_tx.h +++ b/net/smc/smc_tx.h @@ -20,11 +20,15 @@ static inline int smc_tx_prepared_sends(struct smc_connection *conn) { + struct smc_buf_desc *sndbuf_desc = READ_ONCE(conn->sndbuf_desc); union smc_host_cursor sent, prep; + if (!sndbuf_desc) + return 0; + smc_curs_copy(&sent, &conn->tx_curs_sent, conn); smc_curs_copy(&prep, &conn->tx_curs_prep, conn); - return smc_curs_diff(conn->sndbuf_desc->len, &sent, &prep); + return smc_curs_diff(sndbuf_desc->len, &sent, &prep); } void smc_tx_pending(struct smc_connection *conn);