From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793212655; b=EJNEZEdEM3UUBu6pDBnFOZo4VdAnSl+vkBvEwDt061TwpqNsulWkA11g1lKJ6JzeWugC sF7TLDMIJAWGaVGQR2Ei1vTTXLa1ZpL5srbKL0P9Va9a4yJ/ctSft1ylfQ2s3EdU8zFPP XsK8N9TcTKILKhH1DKgovaoRbwx3457/eC+E96qM8ksGjkz2p8JyVUzdtyb/R7Smnf8Ag aC0rHp2/oCXAeW3S4j7lI8eJYpPus1XQZe4ZP2hzROePwdS3mpXV8Ld0KwP06t36XLsZR fvBZgLe91+H3NMCISC4dApFBPmEuWBqxc9T8HD4+EsE5e3E9FOZeyqaTHWprswZRrxQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793212655; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=DArGWEaQecfLCdsu7CcYxYmbr04ivOZsnBAadLmRpzc=; b=xetcDoF//Rg97XJAQMwhf8bM0VwWrdSHj5BPKV1W0yQLavaUPvzHPhzD5m8UfHK+sxwi ibyzMmVDqr7Oa35sfF21vdUIYG+kkERhMGABC1tbER1oLla3+u52c3lVKoMf67LxZXPcZ M6uHh5RY8dM2E6Pwoi9+IU0IF6SHMak4NmjWFIDNOmtFDRpDyrpN3K88pI8q5An1GxZMJ zf82j5zQ+XbTKJAx8lhYxUIMTijkiygr7vnxmSnFqTqoaw7bgK8CKxi73CAfiFh2iKCAd Wf/cNQmNr9yDUcBSWpyeAm4PkY58D/2INPAc/kml5gvQOHkwsIwYrenDeB+RpufPXOw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=qmreAPd9; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 24EDB606A31A; Wed, 28 Oct 2026 18:37:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=qmreAPd9 Received: by smtp.kernel.org (Postfix) with ESMTPSA id 74C811F01825; Wed, 28 Oct 2026 18:37:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793212655; bh=DArGWEaQecfLCdsu7CcYxYmbr04ivOZsnBAadLmRpzc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=qmreAPd945bqwaAdHhaOtQUcCeJi/tC3D9EKeteehm19sd60yxoaX1gkn30zHd+xB nktA9+AEhFuNU0wTUOiskKPnUIAUvFk88iQFo4eG+G5C0mW7N1bTJTGuQnJXa/djkf VUbTkw8hkEBEMypBdgug3wWkU/IEyMDJi26jQbZc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Binbin Deng <18983559317@163.com>, Eric Dumazet , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.1 0230/1887] net/mctp: publish the mctp_dev only after it is initialised Date: Wed, 28 Oct 2026 17:38:46 +0100 Message-ID: <20261028170504.465764738@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028170459.200466217@linuxfoundation.org> References: <20261028170459.200466217@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Binbin Deng <18983559317@163.com> [ Upstream commit aadf655e8ea9a8ffa24bb8d69f504572e8d18181 ] mctp_add_dev() links the new mctp_dev into dev->mctp_ptr before mdev->dev is assigned, so a reader that picks the device up in that window dereferences a net_device pointer that is still NULL: KASAN: null-ptr-deref in range [0x00000000000000b0-0x00000000000000b7] Call Trace: ? __pfx_mctp_sendmsg (./include/linux/sockptr.h:49) ? __pfx_mctp_dst_output (net/mctp/route.c:41) ? selinux_socket_sendmsg (security/selinux/hooks.c:5278) ____sys_sendmsg (net/socket.c:775 (discriminator 1) net/socket.c:790 (discriminator 1) net/socket.c:2684 (discriminator 1)) ? __pfx_____sys_sendmsg (net/socket.c:1131) ? __pfx_copy_msghdr_from_user (net/socket.c:2590) ? update_cfs_rq_load_avg (kernel/sched/fair.c:5478) ___sys_sendmsg (net/socket.c:2738) ? __pfx____sys_sendmsg (net/socket.c:2625) ? perf_event_task_tick (./include/linux/rcupdate.h:838) ? sched_tick (kernel/sched/core.c:5818) ? clockevents_program_event (kernel/time/clockevents.c:372) ? fdget (./include/linux/rcupdate.h:873 fs/file.c:1100) __sys_sendmsg (net/socket.c:2770) ? __pfx___sys_sendmsg (net/socket.c:2751) do_syscall_64 (arch/x86/entry/syscall_64.c:63) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Fix by publishing only once the object is fully initialised: __mctp_dev_get() runs under rcu_read_lock() only and hands this object to readers as soon as mctp_ptr is assigned, so they must never observe mdev->dev == NULL. Fixes: 583be982d934 ("mctp: Add device handling and netlink interface") Signed-off-by: Binbin Deng <18983559317@163.com> Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/729830b8.130.1a0c945579d.Coremail.18983559317@163.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/mctp/device.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/net/mctp/device.c b/net/mctp/device.c index fd368249246df..47407c07afc27 100644 --- a/net/mctp/device.c +++ b/net/mctp/device.c @@ -352,13 +352,13 @@ static struct mctp_dev *mctp_add_dev(struct net_device *dev) mdev->net = mctp_default_net(dev_net(dev)); - /* associate to net_device */ refcount_set(&mdev->refs, 1); - rcu_assign_pointer(dev->mctp_ptr, mdev); - dev_hold(dev); mdev->dev = dev; + /* Associate to net_device, publish the mdev. */ + rcu_assign_pointer(dev->mctp_ptr, mdev); + return mdev; } -- 2.53.0