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 E8E8034B437; Sat, 17 Oct 2026 16:59:57 +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=1792256399; cv=none; b=OnBDXZCfUN667q3kGCjf6i7qYUfJfqtPpHPUaWzm8AQAGWGTSmDYIv9cJebbUXukQwFb85/Bbtd0K3k+un28y0FlwX4h6cgHxcLV1Neu99wZAN/xByVbdPBgPvSunqtcgS5syht7MpmSsBUYs7zn3yhhHN4oxwZpNvhjCSakuPg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792256399; c=relaxed/simple; bh=3ekHhoJqM/Z2fPLsWljQhZRpom8iDoLFclhdJGD5yH0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bIjpYL/sy8hJ+oR//2suQRzK6UKXFLU1NSB6bUvVxRtlWUcMquSutZlGM0YZ/6puRtyUMDubajCLbwBddXTbQDXuIK0YFoGsQNt7yZek0pVhWpZRT+Cr/QCfqhPj64vBw5E1CuR7bIGTBm4E6RI6J1UfGhyTR0C5MAB+hI+Xu9M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=06/k6V6j; 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="06/k6V6j" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 063FE1F000C4; Sat, 17 Oct 2026 16:59:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792256397; bh=v+uhWlNUyP+CiPVG149paIjHoMX/UghahuZkZpEbfb0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=06/k6V6jvyfseS4qT9aq0A1/B3z+0VinB6+l3ajKPI9R6mmIsKQr/0kupiass5AFy 9F9LpSrNxDUAWiyMGfVaxhbUGa5kpzuGqdxPaOhm7BnwUBIxrSn9Z3ZiE/26EQj1m+ DT3h5BwqVhHKq/F+l+NnH1T8dDUwmNAMgnVshofE= 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 6.6 0206/1674] net/mctp: publish the mctp_dev only after it is initialised Date: Sat, 17 Oct 2026 17:41:18 +0200 Message-ID: <20261017160436.437653685@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261017160431.119607952@linuxfoundation.org> References: <20261017160431.119607952@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 6.6-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 67576cb2728ec..ee430b73b0976 100644 --- a/net/mctp/device.c +++ b/net/mctp/device.c @@ -344,13 +344,13 @@ 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