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=1794272901; b=JYHFQdx9rXBxDBHy5V+Bgpz2B3U/cjUaUZiLiGWyF6ftc9nJ9tNxPJZ4qOtpbg14OJDO R57n6VSyoMN5ZH62f8hhbDqRZmlis75wf2rBfMBv7HXkctnZBrsmpXWo2ZoWEdjSV0W79 wUQ471TROqaPz7BhoO8GYbox1U9HZDIrfaQG0LtMUzuCdNRk3z9ktWaYSucygtsI/eh0C MewE0exS8OHyKpZ0zgQ8d+WAsr15Mb3sd8L1MUQEOOytMN7bPwB4RrHw15WNlGM5hPhAz S/Rt3ukL4/d2WJsD7K4cQfviNHX4pZh+LLtHcN/j12byTNC56ATw3bOFgEd4uDtss9A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794272901; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=OZJ8Iv1zQhfITEXErtF1Qcx2S21sYspWRiSn6gfJ7gg=; b=wEuNSAIwuB7spVVRLptjAgRpA6c2DCrEbpnhPYZvant3qRj6CLKqj664AjlS04lhLq/I n64NNFq/RVq1iYx9UomGS7pSmMXPNYeRGTkCJ6IT8WE32Kbxa3BBDcQBuNKFDmz4j3/V6 Z5XHeb28hFdhNRC0xppME60YqZ3/34R/m5g3xdggUX5/DxzMeJQgdFPZtsVvbdlASMdfY wg6wQgxFkduuHI6X7gM15N5SsqV1+cYhofJJPkkJMvFJpf0C6mMkYs4N7F7//0OlW1jQ1 FCjesiEneMtIeIr9kxkua4vePKMQJFnRf38Q8ZT3OHkDhSBZQo7iRyUBGSu3wU6yGKA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b="m/vxR5HX"; 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 E2EC2606A31C for ; Tue, 10 Nov 2026 01:08:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=m/vxR5HX Received: by smtp.kernel.org (Postfix) with ESMTPSA id C32DC1F0089F; Tue, 10 Nov 2026 01:08:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794272900; bh=OZJ8Iv1zQhfITEXErtF1Qcx2S21sYspWRiSn6gfJ7gg=; h=From:To:Cc:Subject:Date; b=m/vxR5HXH6Z65xeK+dPJa5CIp9GcRi4a9+t4eHbmi7+A2tQnPiAw37OMH3y9uoeQo eaiYbQ4wSx8XQ/0Zk/Pa9kZOn4hNwNvdfQmFiD1c37rZHvkMAUoNyD0Se0ihNcMEV1 mRuacY8a1pG/uVI5qky6WhbbvMJ78rwmrbgYBeI7NLc72bve+LUVqTGDmc/DQYpTao zeLPJUvvDX41Vvul13Kkr9gMLIZVxVQ9LPT1/ZfJwJsxPKv2KukLGUXeDnSHTuk+Wd cDHXL5coJTH8OsENeA1v81dZsQsjI34Biar2Pp9QgFyReWOB9sFctBwplBjmBEspD7 SSETlS+uhygxg== From: Sasha Levin To: eklavyasingh2106@gmail.com, akpm@linux-foundation.org, joseph.qi@linux.alibaba.com, mark@fasheh.com, jlbec@evilplan.org, heming.zhao@suse.com, kartikey406@gmail.com, zzzccc427@gmail.com Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] ocfs2/heartbeat: serialize concurrent writes to a region's dev attribute" failed to apply to 6.12-stable tree Date: Mon, 9 Nov 2026 20:08:18 -0500 Message-ID: <20261109200818-failed-6.12-0a8f258c0f01@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.12-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y git checkout FETCH_HEAD git cherry-pick -x 0a8f258c0f012314c36b9e4818cdc0178c68f891 # git commit -s git send-email --to '' --in-reply-to '20261109200818-failed-6.12-0a8f258c0f01@kernel.org' --subject-prefix 'PATCH 6.12.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From 0a8f258c0f012314c36b9e4818cdc0178c68f891 Mon Sep 17 00:00:00 2001 From: Eklavya Singh Date: Wed, 21 Oct 2026 02:53:39 +0530 Subject: [PATCH] ocfs2/heartbeat: serialize concurrent writes to a region's dev attribute o2hb_region_dev_store() checks reg->hr_bdev_file to see if the region is already started, but nothing stops two writers from doing that at the same time. configfs only serializes writes through the same open file, so two processes that each open the dev attribute can both get past the check: A: hr_bdev_file is NULL, opens file A, sets hr_bdev_file = A B: hr_bdev_file is NULL, opens file B, sets hr_bdev_file = B A: start fails, fput(hr_bdev_file) drops B, sets it to NULL B: start fails, fput(NULL) Both calls also use the same hr_slots, hr_slot_data and hr_tmp_block, so the error paths can free the slot data twice. syzbot hit the fput(NULL) with an unbound loop device, where every start fails with -EIO. With four threads doing the same thing on a KASAN kernel I get both crashes within a second: BUG: KASAN: double-free in o2hb_unmap_slot_data+0x14d/0x2f0 BUG: kernel NULL pointer dereference, address: 0000000000000158 Add a mutex to the region and hold it in dev_store(), in the block_bytes, start_block and blocks stores, and in dev_show(), since they all look at hr_bdev_file. dev_store() cleans up with goto, so it takes the mutex in a small wrapper rather than with guard(). The mutex is dropped while dev_store() waits for the heartbeat to become steady, which takes seconds, so a read of dev doesn't stall behind a start. hr_bdev_file is already set at that point, so other writers still get -EINVAL, and the cleanup after the wait retakes the mutex. With the patch the same test ran for 10 minutes with lockdep on and nothing was reported. So did a second one, with a working loop device, that interrupts starts during the wait while other threads read and write the attributes. Link: https://lore.kernel.org/20261020212339.46591-1-eklavyasingh2106@gmail.com Fixes: a7f6a5fb4bde ("[PATCH] OCFS2: The Second Oracle Cluster Filesystem") Signed-off-by: Eklavya Singh Signed-off-by: Andrew Morton Reported-by: Closes: https://syzkaller.appspot.com/bug?extid=5d4e96acd0febccb5e87 Reviewed-by: Joseph Qi Cc: Mark Fasheh Cc: Joel Becker Cc: Heming Zhao Cc: Deepanshu Kartikey Cc: Cen Zhang Cc: --- fs/ocfs2/cluster/heartbeat.c | 40 ++++++++++++++++++++++++++++++------ 1 file changed, 34 insertions(+), 6 deletions(-) diff --git a/fs/ocfs2/cluster/heartbeat.c b/fs/ocfs2/cluster/heartbeat.c index b45adc39aacca..7a18e71b507b3 100644 --- a/fs/ocfs2/cluster/heartbeat.c +++ b/fs/ocfs2/cluster/heartbeat.c @@ -269,6 +269,8 @@ struct o2hb_region { struct list_head hr_handler_list; /* Serializes timeout arming against failed-start and teardown. */ struct mutex hr_arming_mutex; + /* Serializes the dev, block_bytes, start_block and blocks attributes. */ + struct mutex hr_dev_mutex; bool hr_stopping; /* last hb status, 0 for success, other value for error. */ @@ -1681,6 +1683,7 @@ static ssize_t o2hb_region_block_bytes_store(struct config_item *item, unsigned long block_bytes; unsigned int block_bits; + guard(mutex)(®->hr_dev_mutex); if (reg->hr_bdev_file) return -EINVAL; @@ -1710,6 +1713,7 @@ static ssize_t o2hb_region_start_block_store(struct config_item *item, char *p = (char *)page; ssize_t ret; + guard(mutex)(®->hr_dev_mutex); if (reg->hr_bdev_file) return -EINVAL; @@ -1736,6 +1740,7 @@ static ssize_t o2hb_region_blocks_store(struct config_item *item, char *p = (char *)page; int ret; + guard(mutex)(®->hr_dev_mutex); if (reg->hr_bdev_file) return -EINVAL; @@ -1753,10 +1758,12 @@ static ssize_t o2hb_region_blocks_store(struct config_item *item, static ssize_t o2hb_region_dev_show(struct config_item *item, char *page) { + struct o2hb_region *reg = to_o2hb_region(item); unsigned int ret = 0; - if (to_o2hb_region(item)->hr_bdev_file) - ret = sprintf(page, "%pg\n", reg_bdev(to_o2hb_region(item))); + guard(mutex)(®->hr_dev_mutex); + if (reg->hr_bdev_file) + ret = sprintf(page, "%pg\n", reg_bdev(reg)); return ret; } @@ -1872,11 +1879,9 @@ static int o2hb_populate_slot_data(struct o2hb_region *reg) * this is acting as commit; we set up all of hr_bdev_file and hr_task or * nothing */ -static ssize_t o2hb_region_dev_store(struct config_item *item, - const char *page, - size_t count) +static ssize_t __o2hb_region_dev_store(struct o2hb_region *reg, + const char *page, size_t count) { - struct o2hb_region *reg = to_o2hb_region(item); struct task_struct *hb_task; long fd; int sectsize; @@ -1884,6 +1889,8 @@ static ssize_t o2hb_region_dev_store(struct config_item *item, ssize_t ret = -EINVAL; int live_threshold; + lockdep_assert_held(®->hr_dev_mutex); + if (reg->hr_bdev_file) return -EINVAL; @@ -1987,9 +1994,15 @@ static ssize_t o2hb_region_dev_store(struct config_item *item, wake_up_process(hb_task); + /* + * Don't hold hr_dev_mutex across the wait, which can take seconds. + * hr_bdev_file is already set, so other writers still get -EINVAL. + */ + mutex_unlock(®->hr_dev_mutex); ret = wait_event_interruptible(o2hb_steady_queue, atomic_read(®->hr_steady_iterations) == 0 || reg->hr_node_deleted); + mutex_lock(®->hr_dev_mutex); if (ret) { atomic_set(®->hr_steady_iterations, 0); reg->hr_aborted_start = 1; @@ -2041,6 +2054,20 @@ static ssize_t o2hb_region_dev_store(struct config_item *item, return ret; } +static ssize_t o2hb_region_dev_store(struct config_item *item, + const char *page, + size_t count) +{ + struct o2hb_region *reg = to_o2hb_region(item); + ssize_t ret; + + mutex_lock(®->hr_dev_mutex); + ret = __o2hb_region_dev_store(reg, page, count); + mutex_unlock(®->hr_dev_mutex); + + return ret; +} + static ssize_t o2hb_region_pid_show(struct config_item *item, char *page) { struct o2hb_region *reg = to_o2hb_region(item); @@ -2143,6 +2170,7 @@ static struct config_item *o2hb_heartbeat_group_make_item(struct config_group *g INIT_LIST_HEAD(®->hr_all_item); mutex_init(®->hr_arming_mutex); + mutex_init(®->hr_dev_mutex); reg->hr_stopping = true; INIT_DELAYED_WORK(®->hr_write_timeout_work, o2hb_write_timeout); INIT_DELAYED_WORK(®->hr_nego_timeout_work, o2hb_nego_timeout); -- 2.53.0