[PATCH net v2 1/2] net/smc: unregister the connection before draining the rx tasklet
From: Bryam Vargas via B4 Relay <devnull+hexlabsecurity.proton.me@kernel.org>
Date: 2026-08-08 07:21:24
Also in:
b4-sent, linux-rdma, linux-s390, lkml
Subsystem:
networking [general], shared memory communications (smc) sockets, the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, D. Wythe, Dust Li, Sidraya Jayagond, Mahanta Jambigi, Linus Torvalds
From: Bryam Vargas <redacted>
smc_conn_free() calls smc_ism_unset_conn() only while the link group is
still on its device list, and never sets conn->killed.
smc_lgr_terminate_sched() unlinks the group immediately and defers killing
its connections to a work item, so a connection freed in that window keeps
its smcd->conn[] slot with both gates in smcd_handle_irq() open, and the
device can re-arm the receive tasklet after tasklet_kill() has returned. On
the DMB-nocopy path the ghost send buffer is freed right after that drain,
so the re-armed tasklet dereferences it.
Unregister unconditionally and drain before the detach at both teardown
sites, mirroring rmb_desc, which smc_buf_unuse() releases after the drain.
Clear conn->sndbuf_desc before freeing it as well, so a reader that samples
the pointer cannot get one that is already freed.
Fixes: ae2be35cbed2 ("net/smc: {at|de}tach sndbuf to peer DMB if supported")
Cc: stable@vger.kernel.org
Signed-off-by: Bryam Vargas <redacted>
---
net/smc/smc_core.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index b4208cb186c5..181647982490 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c@@ -1209,14 +1209,16 @@ static void smcd_buf_detach(struct smc_connection *conn) { struct smcd_dev *smcd = conn->lgr->smcd; u64 peer_token = conn->peer_token; + struct smc_buf_desc *buf_desc; if (!conn->sndbuf_desc) return; smc_ism_detach_dmb(smcd, peer_token); - kfree(conn->sndbuf_desc); + buf_desc = conn->sndbuf_desc; conn->sndbuf_desc = NULL; + kfree(buf_desc); } static void smc_buf_unuse(struct smc_connection *conn,
@@ -1268,11 +1270,10 @@ void smc_conn_free(struct smc_connection *conn) goto lgr_put; if (lgr->is_smcd) { - if (!list_empty(&lgr->list)) - smc_ism_unset_conn(conn); + smc_ism_unset_conn(conn); + tasklet_kill(&conn->rx_tsklet); if (smc_ism_support_dmb_nocopy(lgr->smcd)) smcd_buf_detach(conn); - tasklet_kill(&conn->rx_tsklet); } else { smc_cdc_wait_pend_tx_wr(conn); if (current_work() != &conn->abort_work)
@@ -1525,12 +1526,12 @@ static void smc_conn_kill(struct smc_connection *conn, bool soft) smc_sk_wake_ups(smc); if (conn->lgr->is_smcd) { smc_ism_unset_conn(conn); - if (smc_ism_support_dmb_nocopy(conn->lgr->smcd)) - smcd_buf_detach(conn); if (soft) tasklet_kill(&conn->rx_tsklet); else tasklet_unlock_wait(&conn->rx_tsklet); + if (smc_ism_support_dmb_nocopy(conn->lgr->smcd)) + smcd_buf_detach(conn); } else { smc_cdc_wait_pend_tx_wr(conn); }
--
2.55.0