From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 37B8B470430; Tue, 21 Jul 2026 19:49:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784663370; cv=none; b=ON7WmPtY6ypuHC/CjOI1qY4UmV+xihcxqyIa4xSt5gDUW08wxDTJC3pcU+j52zwXmfuJDlEZ/fLFFLTaoHaPWJZeX+/AbhfjqsbGbHO10afoEwFkiLfeE4hefqs2urmPIayACmINQav6nVhU7ESWRKVhyNqfTH6PIqhLlAgR+cE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784663370; c=relaxed/simple; bh=HiPqBiPSQtVwUz+93K8QDqYROwZEWff1h/iEe3CIS/4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SG7p8CStxlPZ0AYq8cjLbYioeQbnLssQj8TeA8yApqdUeNQaZS2cGgY8fSw+r1KxyL6h6jvfa4VaCHvMn2LqSxaMTdhtmNRjeSL48BeMRBoIFc2R6hVtHN1E4GiBcq7JIEyl4NVg8TLrdQt43tq1SoBlgV7qELD9J0nFb3hWYt8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=FfDzMjfD; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="FfDzMjfD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 98A421F00A3A; Tue, 21 Jul 2026 19:49:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784663369; bh=YdCI/kQeueCPJEh+Kxkqc3dtLib2CeVVNNWU+ttfEw8=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=FfDzMjfDUF8a0hYqzeBP1bHy7ZWUr5FKxRj3NiVvw0rJJSFAv+YDjwU6vB4hjlxuD 9nB7sOO0aslE7xz2QlhnXXkSNqToD2Mw2bAOkS6qlZ2yobtFCPhZ4M3dVPqLIs0NSN 0/SPNYeglEkloOU6ARfkhnfJDty3lVg170uNR8gg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Michael Nemanov , Chuck Lever , Anna Schumaker , Sasha Levin Subject: [PATCH 6.12 0798/1276] SUNRPC: pin upper rpc_clnt across the TLS connect_worker Date: Tue, 21 Jul 2026 17:20:41 +0200 Message-ID: <20260721152503.931615062@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152446.065700225@linuxfoundation.org> References: <20260721152446.065700225@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chuck Lever [ Upstream commit 46bc86c833956219bbfd246c1ffd832a479c5199 ] The TLS connect path has a use-after-free: nothing pins the upper rpc_clnt across the delayed connect_worker. xs_connect() stores task->tk_client in sock_xprt::clnt as a raw pointer and queues the worker; for TLS-secured transports that worker is xs_tcp_tls_setup_socket(), which reads several fields out of the saved pointer (cl_timeout, cl_program, cl_prog, cl_vers, cl_cred, cl_stats) to construct the args for the inner handshake rpc_clnt. The xprt does not reference the rpc_clnt; the rpc_clnt references the xprt. xs_destroy() does cancel the connect_worker, but it runs only when the xprt's refcount drops to zero, which cannot happen until the rpc_clnt releases its cl_xprt reference in rpc_free_client_work(). When a TLS handshake fails fatally (for example, an mTLS mount whose client cert does not match the server), the connecting task is woken with -EACCES and exits, the mount caller invokes rpc_shutdown_client(), and the upper rpc_clnt is freed before the queued connect_worker fires. xs_tcp_tls_setup_socket() then dereferences the freed clnt, producing the refcount_t underflow Michael Nemanov reported. Take a reference on the upper rpc_clnt in xs_connect() for TLS transports via a new rpc_hold_client() helper, and drop it in the connect_worker's exit path with rpc_release_client(). The xprt_lock_connect() / xprt_unlock_connect() pairing already serialises xs_connect() with xs_tcp_tls_setup_socket(), so the take and release are balanced one-for-one. The non-TLS connect worker (xs_tcp_setup_socket) never reads sock_xprt::clnt, so leave that path alone and avoid the clnt-holds-xprt-holds-clnt cycle that would otherwise prevent xprt destruction. Reported-by: Michael Nemanov Closes: https://lore.kernel.org/linux-nfs/40e3d522-dfcf-4fc1-9c55-b5e81f1536d5@vastdata.com/ Fixes: 75eb6af7acdf ("SUNRPC: Add a TCP-with-TLS RPC transport class") Signed-off-by: Chuck Lever Tested-by: Michael Nemanov Reviewed-by: Michael Nemanov Signed-off-by: Anna Schumaker Signed-off-by: Sasha Levin --- include/linux/sunrpc/clnt.h | 1 + net/sunrpc/clnt.c | 19 +++++++++++++++++-- net/sunrpc/xprtsock.c | 11 ++++++++++- 3 files changed, 28 insertions(+), 3 deletions(-) diff --git a/include/linux/sunrpc/clnt.h b/include/linux/sunrpc/clnt.h index 5321585c778fcc..bd6ac060450cb6 100644 --- a/include/linux/sunrpc/clnt.h +++ b/include/linux/sunrpc/clnt.h @@ -186,6 +186,7 @@ int rpc_switch_client_transport(struct rpc_clnt *, const struct rpc_timeout *); void rpc_shutdown_client(struct rpc_clnt *); +void rpc_hold_client(struct rpc_clnt *); void rpc_release_client(struct rpc_clnt *); void rpc_task_release_transport(struct rpc_task *); void rpc_task_release_client(struct rpc_task *); diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c index e492655cb2212e..e88e21c2ab3299 100644 --- a/net/sunrpc/clnt.c +++ b/net/sunrpc/clnt.c @@ -1026,8 +1026,23 @@ rpc_free_auth(struct rpc_clnt *clnt) return NULL; } -/* - * Release reference to the RPC client +/** + * rpc_hold_client - acquire a reference on an rpc_clnt + * @clnt: rpc_clnt to pin + * + * Pairs with rpc_release_client(). + */ +void rpc_hold_client(struct rpc_clnt *clnt) +{ + refcount_inc(&clnt->cl_count); +} + +/** + * rpc_release_client - release a reference on an rpc_clnt + * @clnt: rpc_clnt to release + * + * Pairs with rpc_hold_client(). The rpc_clnt's resources are + * freed once its reference count drops to zero. */ void rpc_release_client(struct rpc_clnt *clnt) diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c index f5b22267fadf46..56819b6a7bde2f 100644 --- a/net/sunrpc/xprtsock.c +++ b/net/sunrpc/xprtsock.c @@ -2770,6 +2770,7 @@ static void xs_tcp_tls_setup_socket(struct work_struct *work) out_unlock: current_restore_flags(pflags, PF_MEMALLOC); upper_transport->clnt = NULL; + rpc_release_client(upper_clnt); xprt_unlock_connect(upper_xprt, upper_transport); return; @@ -2817,7 +2818,15 @@ static void xs_connect(struct rpc_xprt *xprt, struct rpc_task *task) } else dprintk("RPC: xs_connect scheduled xprt %p\n", xprt); - transport->clnt = task->tk_client; + /* + * Only the TLS connect_worker reads transport->clnt; pinning + * the upper rpc_clnt unconditionally would form a cycle with + * cl_xprt and prevent xprt destruction. + */ + if (xprt->xprtsec.policy != RPC_XPRTSEC_NONE) { + rpc_hold_client(task->tk_client); + transport->clnt = task->tk_client; + } queue_delayed_work(xprtiod_workqueue, &transport->connect_worker, delay); -- 2.53.0