CVE-2023-54281
Description
In the Linux kernel, the following vulnerability has been resolved:
btrfs: release path before inode lookup during the ino lookup ioctl
During the ino lookup ioctl we can end up calling btrfs_iget() to get an inode reference while we are holding on a root's btree. If btrfs_iget() needs to lookup the inode from the root's btree, because it's not currently loaded in memory, then it will need to lock another or the same path in the same root btree. This may result in a deadlock and trigger the following lockdep splat:
WARNING: possible circular locking dependency detected 6.5.0-rc7-syzkaller-00004-gf7757129e3de #0 Not tainted ------------------------------------------------------ syz-executor277/5012 is trying to acquire lock: ffff88802df41710 (btrfs-tree-01){++++}-{3:3}, at: __btrfs_tree_read_lock+0x2f/0x220 fs/btrfs/locking.c:136
but task is already holding lock: ffff88802df418e8 (btrfs-tree-00){++++}-{3:3}, at: __btrfs_tree_read_lock+0x2f/0x220 fs/btrfs/locking.c:136
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (btrfs-tree-00){++++}-{3:3}: down_read_nested+0x49/0x2f0 kernel/locking/rwsem.c:1645 __btrfs_tree_read_lock+0x2f/0x220 fs/btrfs/locking.c:136 btrfs_search_slot+0x13a4/0x2f80 fs/btrfs/ctree.c:2302 btrfs_init_root_free_objectid+0x148/0x320 fs/btrfs/disk-io.c:4955 btrfs_init_fs_root fs/btrfs/disk-io.c:1128 [inline] btrfs_get_root_ref+0x5ae/0xae0 fs/btrfs/disk-io.c:1338 btrfs_get_fs_root fs/btrfs/disk-io.c:1390 [inline] open_ctree+0x29c8/0x3030 fs/btrfs/disk-io.c:3494 btrfs_fill_super+0x1c7/0x2f0 fs/btrfs/super.c:1154 btrfs_mount_root+0x7e0/0x910 fs/btrfs/super.c:1519 legacy_get_tree+0xef/0x190 fs/fs_context.c:611 vfs_get_tree+0x8c/0x270 fs/super.c:1519 fc_mount fs/namespace.c:1112 [inline] vfs_kern_mount+0xbc/0x150 fs/namespace.c:1142 btrfs_mount+0x39f/0xb50 fs/btrfs/super.c:1579 legacy_get_tree+0xef/0x190 fs/fs_context.c:611 vfs_get_tree+0x8c/0x270 fs/super.c:1519 do_new_mount+0x28f/0xae0 fs/namespace.c:3335 do_mount fs/namespace.c:3675 [inline] __do_sys_mount fs/namespace.c:3884 [inline] __se_sys_mount+0x2d9/0x3c0 fs/namespace.c:3861 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
-> #0 (btrfs-tree-01){++++}-{3:3}: check_prev_add kernel/locking/lockdep.c:3142 [inline] check_prevs_add kernel/locking/lockdep.c:3261 [inline] validate_chain kernel/locking/lockdep.c:3876 [inline] __lock_acquire+0x39ff/0x7f70 kernel/locking/lockdep.c:5144 lock_acquire+0x1e3/0x520 kernel/locking/lockdep.c:5761 down_read_nested+0x49/0x2f0 kernel/locking/rwsem.c:1645 __btrfs_tree_read_lock+0x2f/0x220 fs/btrfs/locking.c:136 btrfs_tree_read_lock fs/btrfs/locking.c:142 [inline] btrfs_read_lock_root_node+0x292/0x3c0 fs/btrfs/locking.c:281 btrfs_search_slot_get_root fs/btrfs/ctree.c:1832 [inline] btrfs_search_slot+0x4ff/0x2f80 fs/btrfs/ctree.c:2154 btrfs_lookup_inode+0xdc/0x480 fs/btrfs/inode-item.c:412 btrfs_read_locked_inode fs/btrfs/inode.c:3892 [inline] btrfs_iget_path+0x2d9/0x1520 fs/btrfs/inode.c:5716 btrfs_search_path_in_tree_user fs/btrfs/ioctl.c:1961 [inline] btrfs_ioctl_ino_lookup_user+0x77a/0xf50 fs/btrfs/ioctl.c:2105 btrfs_ioctl+0xb0b/0xd40 fs/btrfs/ioctl.c:4683 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl+0xf8/0x170 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
other info ---truncated---
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
A locking deadlock in the btrfs ino lookup ioctl is fixed by releasing the btree path before calling btrfs_iget().
Root
Cause
During the btrfs ino lookup ioctl, the kernel held a read lock on a root's btree path and then called btrfs_iget() to get an inode reference. If the inode was not in memory, btrfs_iget() would attempt to lock another (or the same) btree path to read the inode from disk, creating a potential deadlock. This violates lock ordering and can trigger a lockdep warning about a circular locking dependency [Description].
Exploitation
An attacker with local access and the ability to invoke the BTRFS_IOC_INO_LOOKUP ioctl can trigger this deadlock condition. The vulnerability does not require special privileges beyond the ability to open a btrfs file descriptor and call the ioctl. By causing a specific sequence of operations—such as forcing an inode cache miss while holding the btree path—the attacker can hang the filesystem, leading to a denial of service [Description].
Impact
A successful exploit results in a deadlock that causes the system to become unresponsive. The filesystem operations stall, potentially affecting all processes relying on btrfs. This is a denial-of-service vulnerability with a CVSS v3 score of 5.5 (medium severity) [Header].
Mitigation
Patches have been backported to stable kernel branches to release the btree path before performing the inode lookup. Linux distributions incorporating the fix (e.g., commit 380bbd46d61c or 7390bb377b5b) are no longer vulnerable. Users should update their kernel to the latest stable release containing the backport [1], [2].
AI Insight generated on May 19, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.
Affected products
1Patches
57390bb377b5f380bbd46d61c50e385d98b2a6fdce81e425bee34a82e890aVulnerability mechanics
Generated on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.
References
5- git.kernel.org/stable/c/380bbd46d61c894a8dcaace09e54bc7426d81014nvd
- git.kernel.org/stable/c/50e385d98b2a52480836ea41c142b81eeeb277afnvd
- git.kernel.org/stable/c/6fdce81e425be112f1ca129776f4041afeaad413nvd
- git.kernel.org/stable/c/7390bb377b5fb3be23cb021e0f184d1f576be7d6nvd
- git.kernel.org/stable/c/ee34a82e890a7babb5585daf1a6dd7d4d1cf142anvd
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