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

btrfs: fix block group refcount race in btrfs_create_pending_block_groups()

Block group creation is done in two phases, which results in a slightly
unintuitive property: a block group can be allocated/deallocated from
after btrfs_make_block_group() adds it to the space_info with
btrfs_add_bg_to_space_info(), but before creation is completely completed
in btrfs_create_pending_block_groups(). As a result, it is possible for a
block group to go unused and have 'btrfs_mark_bg_unused' called on it
concurrently with 'btrfs_create_pending_block_groups'. This causes a
number of issues, which were fixed with the block group flag
'BLOCK_GROUP_FLAG_NEW'.

However, this fix is not quite complete. Since it does not use the
unused_bg_lock, it is possible for the following race to occur:

btrfs_create_pending_block_groups btrfs_mark_bg_unused
if list_empty // false
list_del_init
clear_bit
else if (test_bit) // true
list_move_tail

And we get into the exact same broken ref count and invalid new_bgs
state for transaction cleanup that BLOCK_GROUP_FLAG_NEW was designed to
prevent.

The broken refcount aspect will result in a warning like:

[1272.943527] refcount_t: underflow; use-after-free.
[1272.943967] WARNING: CPU: 1 PID: 61 at lib/refcount.c:28 refcount_warn_saturate+0xba/0x110
[1272.944731] Modules linked in: btrfs virtio_net xor zstd_compress raid6_pq null_blk [last unloaded: btrfs]
[1272.945550] CPU: 1 UID: 0 PID: 61 Comm: kworker/u32:1 Kdump: loaded Tainted: G W 6.14.0-rc5+ #108
[1272.946368] Tainted: [W]=WARN
[1272.946585] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014
[1272.947273] Workqueue: btrfs_discard btrfs_discard_workfn [btrfs]
[1272.947788] RIP: 0010:refcount_warn_saturate+0xba/0x110
[1272.949532] RSP: 0018:ffffbf1200247df0 EFLAGS: 00010282
[1272.949901] RAX: 0000000000000000 RBX: ffffa14b00e3f800 RCX: 0000000000000000
[1272.950437] RDX: 0000000000000000 RSI: ffffbf1200247c78 RDI: 00000000ffffdfff
[1272.950986] RBP: ffffa14b00dc2860 R08: 00000000ffffdfff R09: ffffffff90526268
[1272.951512] R10: ffffffff904762c0 R11: 0000000063666572 R12: ffffa14b00dc28c0
[1272.952024] R13: 0000000000000000 R14: ffffa14b00dc2868 R15: 000001285dcd12c0
[1272.952850] FS: 0000000000000000(0000) GS:ffffa14d33c40000(0000) knlGS:0000000000000000
[1272.953458] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[1272.953931] CR2: 00007f838cbda000 CR3: 000000010104e000 CR4: 00000000000006f0
[1272.954474] Call Trace:
[1272.954655] <TASK>
[1272.954812] ? refcount_warn_saturate+0xba/0x110
[1272.955173] ? __warn.cold+0x93/0xd7
[1272.955487] ? refcount_warn_saturate+0xba/0x110
[1272.955816] ? report_bug+0xe7/0x120
[1272.956103] ? handle_bug+0x53/0x90
[1272.956424] ? exc_invalid_op+0x13/0x60
[1272.956700] ? asm_exc_invalid_op+0x16/0x20
[1272.957011] ? refcount_warn_saturate+0xba/0x110
[1272.957399] btrfs_discard_cancel_work.cold+0x26/0x2b [btrfs]
[1272.957853] btrfs_put_block_group.cold+0x5d/0x8e [btrfs]
[1272.958289] btrfs_discard_workfn+0x194/0x380 [btrfs]
[1272.958729] process_one_work+0x130/0x290
[1272.959026] worker_thread+0x2ea/0x420
[1272.959335] ? __pfx_worker_thread+0x10/0x10
[1272.959644] kthread+0xd7/0x1c0
[1272.959872] ? __pfx_kthread+0x10/0x10
[1272.960172] ret_from_fork+0x30/0x50
[1272.960474] ? __pfx_kthread+0x10/0x10
[1272.960745] ret_from_fork_asm+0x1a/0x30
[1272.961035] </TASK>
[1272.961238] ---[ end trace 0000000000000000 ]---

Though we have seen them in the async discard workfn as well. It is
most likely to happen after a relocation finishes which cancels discard,
tears down the block group, etc.

Fix this fully by taking the lock arou
---truncated---

Metrics

No CVSS v4.0

Attack Vector Local

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00025.

Key SSVC decision points have not yet been added.

Affected Vendors & Products

No data.

No data.

No data.

No data.

Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://git.kernel.org/stable/c/2d8e5168d48a91e7a802d3003e72afb4304bebfa cve-icon cve-icon
https://git.kernel.org/stable/c/9d383a6fc59271aaaf07a33b23b2eac5b9268b7a cve-icon cve-icon
https://git.kernel.org/stable/c/ee56da95f8962b86fec4ef93f866e64c8d025a58 cve-icon cve-icon
https://lore.kernel.org/linux-cve-announce/2025041626-CVE-2025-22115-857c@gregkh/T cve-icon
https://nvd.nist.gov/vuln/detail/CVE-2025-22115 cve-icon
https://www.cve.org/CVERecord?id=CVE-2025-22115 cve-icon
History

Thu, 24 Jul 2025 07:15:00 +0000

Type Values Removed Values Added
References

Thu, 17 Apr 2025 14:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

 cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

threat_severity

Low

Wed, 16 Apr 2025 14:30:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: btrfs: fix block group refcount race in btrfs_create_pending_block_groups() Block group creation is done in two phases, which results in a slightly unintuitive property: a block group can be allocated/deallocated from after btrfs_make_block_group() adds it to the space_info with btrfs_add_bg_to_space_info(), but before creation is completely completed in btrfs_create_pending_block_groups(). As a result, it is possible for a block group to go unused and have 'btrfs_mark_bg_unused' called on it concurrently with 'btrfs_create_pending_block_groups'. This causes a number of issues, which were fixed with the block group flag 'BLOCK_GROUP_FLAG_NEW'. However, this fix is not quite complete. Since it does not use the unused_bg_lock, it is possible for the following race to occur: btrfs_create_pending_block_groups btrfs_mark_bg_unused if list_empty // false list_del_init clear_bit else if (test_bit) // true list_move_tail And we get into the exact same broken ref count and invalid new_bgs state for transaction cleanup that BLOCK_GROUP_FLAG_NEW was designed to prevent. The broken refcount aspect will result in a warning like: [1272.943527] refcount_t: underflow; use-after-free. [1272.943967] WARNING: CPU: 1 PID: 61 at lib/refcount.c:28 refcount_warn_saturate+0xba/0x110 [1272.944731] Modules linked in: btrfs virtio_net xor zstd_compress raid6_pq null_blk [last unloaded: btrfs] [1272.945550] CPU: 1 UID: 0 PID: 61 Comm: kworker/u32:1 Kdump: loaded Tainted: G W 6.14.0-rc5+ #108 [1272.946368] Tainted: [W]=WARN [1272.946585] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014 [1272.947273] Workqueue: btrfs_discard btrfs_discard_workfn [btrfs] [1272.947788] RIP: 0010:refcount_warn_saturate+0xba/0x110 [1272.949532] RSP: 0018:ffffbf1200247df0 EFLAGS: 00010282 [1272.949901] RAX: 0000000000000000 RBX: ffffa14b00e3f800 RCX: 0000000000000000 [1272.950437] RDX: 0000000000000000 RSI: ffffbf1200247c78 RDI: 00000000ffffdfff [1272.950986] RBP: ffffa14b00dc2860 R08: 00000000ffffdfff R09: ffffffff90526268 [1272.951512] R10: ffffffff904762c0 R11: 0000000063666572 R12: ffffa14b00dc28c0 [1272.952024] R13: 0000000000000000 R14: ffffa14b00dc2868 R15: 000001285dcd12c0 [1272.952850] FS: 0000000000000000(0000) GS:ffffa14d33c40000(0000) knlGS:0000000000000000 [1272.953458] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [1272.953931] CR2: 00007f838cbda000 CR3: 000000010104e000 CR4: 00000000000006f0 [1272.954474] Call Trace: [1272.954655] <TASK> [1272.954812] ? refcount_warn_saturate+0xba/0x110 [1272.955173] ? __warn.cold+0x93/0xd7 [1272.955487] ? refcount_warn_saturate+0xba/0x110 [1272.955816] ? report_bug+0xe7/0x120 [1272.956103] ? handle_bug+0x53/0x90 [1272.956424] ? exc_invalid_op+0x13/0x60 [1272.956700] ? asm_exc_invalid_op+0x16/0x20 [1272.957011] ? refcount_warn_saturate+0xba/0x110 [1272.957399] btrfs_discard_cancel_work.cold+0x26/0x2b [btrfs] [1272.957853] btrfs_put_block_group.cold+0x5d/0x8e [btrfs] [1272.958289] btrfs_discard_workfn+0x194/0x380 [btrfs] [1272.958729] process_one_work+0x130/0x290 [1272.959026] worker_thread+0x2ea/0x420 [1272.959335] ? __pfx_worker_thread+0x10/0x10 [1272.959644] kthread+0xd7/0x1c0 [1272.959872] ? __pfx_kthread+0x10/0x10 [1272.960172] ret_from_fork+0x30/0x50 [1272.960474] ? __pfx_kthread+0x10/0x10 [1272.960745] ret_from_fork_asm+0x1a/0x30 [1272.961035] </TASK> [1272.961238] ---[ end trace 0000000000000000 ]--- Though we have seen them in the async discard workfn as well. It is most likely to happen after a relocation finishes which cancels discard, tears down the block group, etc. Fix this fully by taking the lock arou ---truncated---
Title btrfs: fix block group refcount race in btrfs_create_pending_block_groups()
References
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2025-07-24T07:07:18.253Z

Reserved: 2024-12-29T08:45:45.823Z

Link: CVE-2025-22115

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Awaiting Analysis

Published: 2025-04-16T15:16:05.710

Modified: 2025-07-24T07:15:52.840

Link: CVE-2025-22115

cve-icon Redhat

Severity : Low

Publid Date: 2025-04-16T00:00:00Z

Links: CVE-2025-22115 - Bugzilla

cve-icon OpenCVE Enrichment

No data.