Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-07-25T00:00:00 kernel: block: skip sync_blockdev() on surprise removal in bdev_mark_dead() 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H CWE-390

In the Linux kernel, the following vulnerability has been resolved: block: skip sync_blockdev() on surprise removal in bdev_mark_dead() bdev_mark_dead()'s @surprise == true means the device is already gone. The filesystem callback fs_bdev_mark_dead() honours this and skips sync_filesystem(), but the bare block device path (no ->mark_dead op) lost its !surprise guard when the holder ->mark_dead callback was wired up (see Fixes), and now calls sync_blockdev() unconditionally, which can hang forever waiting on writeback that can no longer complete. syzkaller hit this via nvme_reset_work()'s "I/O queues lost" path: nvme_mark_namespaces_dead() -> blk_mark_disk_dead() -> bdev_mark_dead(bdev, true) -> sync_blockdev() blocks in folio_wait_writeback(), wedging the reset worker and every task waiting on it. Skip the sync on surprise removal, matching fs_bdev_mark_dead(); invalidate_bdev() still runs. Orderly removal (surprise == false) is unchanged. Found by FuzzNvme(Syzkaller with FEMU fuzzing framework).

A flaw was found in the Linux kernel's block device handling. When a block device is unexpectedly removed, the `bdev_mark_dead()` function can unconditionally attempt to synchronize the device, even if it is no longer present. This can lead to a system hang, effectively causing a Denial of Service (DoS), as the system waits indefinitely for writeback operations that cannot complete. This vulnerability can be triggered by a local user or process interacting with block devices during surprise removal events.

https://www.cve.org/CVERecord?id=CVE-2026-64326 https://nvd.nist.gov/vuln/detail/CVE-2026-64326 https://lore.kernel.org/linux-cve-announce/2026072512-CVE-2026-64326-8454@gregkh/T