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([2405:201:682f:383f:35e0:2c1e:70f6:a9ef]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39b08ca63b3sm12815116a91.11.2026.09.04.16.57.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Sep 2026 16:57:41 -0700 (PDT) From: Deepanshu Kartikey To: mark@fasheh.com, jlbec@evilplan.org, joseph.qi@linux.alibaba.com, akpm@linux-foundation.org, brauner@kernel.org, jack@suse.cz Cc: zzzccc427@gmail.com, ericterminal@gmail.com, ocfs2-devel@lists.linux.dev, christophe.jaillet@wanadoo.fr, linux-kernel@vger.kernel.org, Deepanshu Kartikey , syzbot+3025e3e8fc0b928af8f5@syzkaller.appspotmail.com Subject: [PATCH] ocfs2: fix use-after-free in o2hb_region_dev_store Date: Sat, 5 Sep 2026 05:27:10 +0530 Message-Id: <20260904235710.16317-1-kartikey406@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Concurrent writes to a region's "dev" attribute can race, letting two tasks both allocate/free reg->hr_slot_data for the same region and causing a use-after-free. Add a per-region mutex to serialize o2hb_region_dev_store() against itself and against o2hb_region_release(). Fixes: 1d3aa0b97c55 ("ocfs2: port block device access to file") Reported-by: syzbot+3025e3e8fc0b928af8f5@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3025e3e8fc0b928af8f5 Tested-by: syzbot+3025e3e8fc0b928af8f5@syzkaller.appspotmail.com Signed-off-by: Deepanshu Kartikey --- fs/ocfs2/cluster/heartbeat.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/fs/ocfs2/cluster/heartbeat.c b/fs/ocfs2/cluster/heartbeat.c index 1c3def99bb07..6f03de1b6d4a 100644 --- a/fs/ocfs2/cluster/heartbeat.c +++ b/fs/ocfs2/cluster/heartbeat.c @@ -273,6 +273,9 @@ struct o2hb_region { /* last hb status, 0 for success, other value for error. */ int hr_last_hb_status; + /* Serializes dev_store() against itself and region_release() */ + struct mutex hr_dev_write_mutex; + }; static inline struct block_device *reg_bdev(struct o2hb_region *reg) @@ -1616,7 +1619,10 @@ static void o2hb_region_release(struct config_item *item) o2hb_quiesce_timeout(reg); o2net_unregister_and_flush_handler_list(®->hr_handler_list); + + mutex_lock(®->hr_dev_write_mutex); o2hb_unmap_slot_data(reg); + mutex_unlock(®->hr_dev_write_mutex); if (reg->hr_bdev_file) fput(reg->hr_bdev_file); @@ -1879,9 +1885,6 @@ static ssize_t o2hb_region_dev_store(struct config_item *item, ssize_t ret = -EINVAL; int live_threshold; - if (reg->hr_bdev_file) - return -EINVAL; - /* We can't heartbeat without having had our node number * configured yet. */ reg->hr_node_num = o2nm_this_node(); @@ -1906,12 +1909,20 @@ static ssize_t o2hb_region_dev_store(struct config_item *item, if (!S_ISBLK(fd_file(f)->f_mapping->host->i_mode)) return -EINVAL; + if (mutex_lock_interruptible(®->hr_dev_write_mutex)) + return -ERESTARTSYS; + + if (reg->hr_bdev_file) { + ret = -EINVAL; + goto out_unlock; + } + reg->hr_bdev_file = bdev_file_open_by_dev(fd_file(f)->f_mapping->host->i_rdev, BLK_OPEN_WRITE | BLK_OPEN_READ, NULL, NULL); if (IS_ERR(reg->hr_bdev_file)) { ret = PTR_ERR(reg->hr_bdev_file); reg->hr_bdev_file = NULL; - return ret; + goto out_unlock; } sectsize = bdev_logical_block_size(reg_bdev(reg)); @@ -2029,6 +2040,8 @@ static ssize_t o2hb_region_dev_store(struct config_item *item, fput(reg->hr_bdev_file); reg->hr_bdev_file = NULL; } +out_unlock: + mutex_unlock(®->hr_dev_write_mutex); return ret; } @@ -2149,6 +2162,8 @@ static struct config_item *o2hb_heartbeat_group_make_item(struct config_group *g config_item_init_type_name(®->hr_item, name, &o2hb_region_type); + mutex_init(®->hr_dev_write_mutex); + /* this is the same way to generate msg key as dlm, for local heartbeat, * name is also the same, so make initial crc value different to avoid * message key conflict. -- 2.34.1