From db51a8658c11a82432b64999519a269c3aabb447 Mon Sep 17 00:00:00 2001 From: Hidayath Khan Date: Thu, 20 Aug 2026 09:46:41 +0200 Subject: [PATCH 1/2] net/smc: stop killed, freed and out_of_sync sharing a byte The three connection state flags are single-bit bitfields, so they occupy one byte of struct smc_connection and every store to one is a read-modify-write of the other two: u8 killed : 1; u8 freed : 1; u8 out_of_sync : 1; They are not written under a common lock. smc_cdc_msg_validate() sets out_of_sync from the receive tasklet, while smc_conn_kill() sets killed from process context under lock_sock(), and the receive path does not defer to the backlog when the socket is owned -- smc_cdc_msg_recv() takes only bh_lock_sock(). Give each flag its own byte so a store no longer touches its neighbours. All readers test them as booleans and are unchanged. struct smc_connection grows by two bytes. Fixes: b286a0651e44 ("net/smc: handle incoming CDC validation message") Cc: stable@vger.kernel.org Reviewed-by: Mahanta Jambigi Signed-off-by: Hidayath Khan Reviewed-by: Simon Horman Link: https://patch.msgid.link/20260820074642.966856-2-hidayath@linux.ibm.com Signed-off-by: Jakub Kicinski --- net/smc/smc.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/net/smc/smc.h b/net/smc/smc.h index 52145df83f6e..427b6d63b993 100644 --- a/net/smc/smc.h +++ b/net/smc/smc.h @@ -277,9 +277,9 @@ struct smc_connection { * 0 for SMC-R, 32 for SMC-D */ u64 peer_token; /* SMC-D token of peer */ - u8 killed : 1; /* abnormal termination */ - u8 freed : 1; /* normal termination */ - u8 out_of_sync : 1; /* out of sync with peer */ + u8 killed; /* abnormal termination */ + u8 freed; /* normal termination */ + u8 out_of_sync; /* out of sync with peer */ }; struct smc_sock { /* smc sock container */ From c924884743e948e25625b7fbf3ee2a9325a204a7 Mon Sep 17 00:00:00 2001 From: Hidayath Khan Date: Thu, 20 Aug 2026 09:46:42 +0200 Subject: [PATCH 2/2] net/smc: fix use-after-free in smc_rx_pipe_buf_release() smc_rx_splice() hands RMB pages to a pipe and takes a socket reference per entry so the smc_sock stays alive until the reader finishes. The connection does not: a concurrent close runs smc_conn_free(), which releases the receive buffer back to the link group pool. smc_rx_pipe_buf_release() tests sk_state before taking the socket lock. The state can change between the test and the lock, and smc_rx_update_cons() then dereferences conn->rmb_desc and walks conn->lgr, which smc_conn_free() has already released. On the is_reg_err path smcr_buf_unuse() frees the descriptor outright, so this is a use-after-free. Take the socket lock first and test conn->freed instead. smc_conn_free() sets that flag before releasing anything, and every caller holds the socket lock. The two paths exclude each other: either the pipe release runs first with everything valid, or it sees the flag and skips the update. Fixes: 9014db202cb7 ("smc: add support for splice()") Cc: stable@vger.kernel.org Reviewed-by: Mahanta Jambigi Signed-off-by: Hidayath Khan Reviewed-by: Simon Horman Link: https://patch.msgid.link/20260820074642.966856-3-hidayath@linux.ibm.com Signed-off-by: Jakub Kicinski --- net/smc/smc_rx.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/net/smc/smc_rx.c b/net/smc/smc_rx.c index 5c9e4d8b57de..197fddc6271f 100644 --- a/net/smc/smc_rx.c +++ b/net/smc/smc_rx.c @@ -115,16 +115,15 @@ static void smc_rx_pipe_buf_release(struct pipe_inode_info *pipe, struct pipe_buffer *buf) { struct smc_spd_priv *priv = (struct smc_spd_priv *)buf->private; + struct smc_connection *conn = &priv->smc->conn; struct smc_sock *smc = priv->smc; - struct smc_connection *conn; struct sock *sk = &smc->sk; - if (sk->sk_state == SMC_CLOSED || - sk->sk_state == SMC_PEERFINCLOSEWAIT || - sk->sk_state == SMC_APPFINCLOSEWAIT) - goto out; - conn = &smc->conn; lock_sock(sk); + if (conn->freed) { + release_sock(sk); + goto out; + } smc_rx_update_cons(smc, priv->len); release_sock(sk); if (atomic_sub_and_test(priv->len, &conn->splice_pending))