CVE-2026-89491

Summary

In the Linux kernel, the following vulnerability has been resolved:

ocfs2: cluster: don't sleep while holding o2hb_live_lock in o2hb_region_pin()

Patch series "ocfs2: cluster: o2hb_region_pin() fixes", v2.

This series fixes three related issues in o2hb_region_pin(), all are from the original implementation in commit: 58a3158a5d17 ("ocfs2/cluster: Pin/unpin o2hb regions"):

1. It is called with o2hb_live_lock (a spinlock) held, but the underlying configfs_depend_item() sleeps (takes inode rwsem and pins the filesystem). This triggers BUG under CONFIG_DEBUG_ATOMIC_SLEEP.

2. When called from the configfs drop_item callback, it creates a lock order inversion: parent inode_lock -> configfs root inode_lock, which can deadlock against subsystem unregistration paths taking root -> parent.

3. If pinning fails partway through o2hb_region_inc_user(), the o2hb_dependent_users counter is leaked and partially-pinned regions are never released, leaving heartbeat regions unprotected on subsequent mounts.

Patch 1 reworks o2hb_region_pin() to drop o2hb_live_lock across each sleeping configfs_depend_item() call, using a config_item reference to keep the region alive while unlocked.

Patch 2 adds a from_callback parameter to select configfs_depend_item_unlocked() when called from configfs context, avoiding the inode_lock nesting.

Patch 3 fixes the error path in o2hb_region_inc_user() to unpin and decrement the counter on failure.

This patch (of 3):

o2hb_region_pin() is always called with the o2hb_live_lock spinlock held (from o2hb_region_inc_user() and o2hb_heartbeat_group_drop_item()), but it calls o2nm_depend_item() -> configfs_depend_item(), which sleeps: it pins the configfs filesystem and takes the configfs root inode rwsem. Under CONFIG_DEBUG_ATOMIC_SLEEP this triggers:

BUG: sleeping function called from invalid context at kernel/locking/rwsem.c in_atomic(): 1, … name: mount.ocfs2 down_write configfs_depend_item o2hb_region_pin o2hb_region_inc_user o2hb_register_callback dlm_register_domain_handlers … ocfs2_dlm_init ocfs2_mount_volume ocfs2_fill_super

Rework o2hb_region_pin() to pin one region at a time with the lock dropped across the sleeping call: under o2hb_live_lock find the next eligible region and take a config_item reference to keep it alive, drop the lock, call o2nm_depend_item(), then retake the lock and record the pin. The config_item_put() is done with the lock released as well, since o2hb_region_release() also acquires o2hb_live_lock and can sleep. The region list may change while unlocked, so the scan restarts from the top after each pin. Local heartbeat still pins only the matching region; global heartbeat pins all eligible regions.

The unpin path is unaffected: configfs_undepend_item() only takes a spinlock and does not sleep.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/49002acc520c61002ad195894ac391c94317d3ba
• https://git.kernel.org/stable/c/ce035f208d68b812d83e5482980f2b1c88a9cd94
• https://git.kernel.org/stable/c/470212a5eefabcc16b8e2f7fe2844b8737fe571c
• https://git.kernel.org/stable/c/af09df89db9a68a1d76df0f75667998135bc8d65

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