From c924884743e948e25625b7fbf3ee2a9325a204a7 Mon Sep 17 00:00:00 2001 From: Hidayath Khan Date: Thu, 20 Aug 2026 09:46:42 +0200 Subject: [PATCH] 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))