# CVE-2025-22115: btrfs: fix block group refcount race in btrfs_create_pending_block_groups() > A race condition in the Linux kernel's btrfs filesystem can cause a use-after-free warning and potential system instability. - **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Any signed-in user - **Attackable:** Local or same network only - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 16 Apr 2025 - **Updated:** 21 Oct 2026 - **Also known as:** AZL-62693, BELL-CVE-2025-22115, DEBIAN-CVE-2025-22115, GHSA-h52v-87c4-f7qg, ROOT-OS-DEBIAN-12-CVE-2025-22115, ROOT-OS-UBUNTU-2404-CVE-2025-22115, SUSE-SU-2025:02439-1, SUSE-SU-2025:02514-1, SUSE-SU-2025:20521-1, SUSE-SU-2025:20524-1, SUSE-SU-2025:20529-1, SUSE-SU-2025:20543-1, SUSE-SU-2025:20547-1, SUSE-SU-2025:20548-1, UBUNTU-CVE-2025-22115 ## What is CVE-2025-22115? CVE-2025-22115 is a high-severity vulnerability in Linux kernel, published on 16 Apr 2025. It can only be exploited from the same machine or local network, with no action from the victim. ### Official 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] [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] [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--- Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization) ## Which versions are affected by CVE-2025-22115? It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `kernel-livepatch-SLE15-SP6-RT_Update_10` | SUSE:Linux Enterprise Live Patching 15 SP6 | All versions | 2-150600.2.1 | | `kernel-livepatch-SLE15-SP6_Update_10` | SUSE:Linux Enterprise Live Patching 15 SP6 | All versions | 2-150600.2.1 | | `kernel-livepatch-MICRO-6-0-RT_Update_6` | SUSE:Linux Micro 6.0 | All versions | 2-3.1 | | `kernel-livepatch-MICRO-6-0-RT_Update_7` | SUSE:Linux Micro 6.0 | All versions | 2-1.3 | | `kernel-livepatch-MICRO-6-0_Update_6` | SUSE:Linux Micro 6.0 | All versions | 2-3.1 | | `kernel-livepatch-MICRO-6-0-RT_Update_6` | SUSE:Linux Micro 6.1 | All versions | 2-3.1 | | `kernel-livepatch-MICRO-6-0-RT_Update_7` | SUSE:Linux Micro 6.1 | All versions | 2-1.3 | | `kernel-livepatch-MICRO-6-0_Update_6` | SUSE:Linux Micro 6.1 | All versions | 2-3.1 | Products: Linux kernel. ## How do I fix CVE-2025-22115? Apply the vendor's patch. ## Is CVE-2025-22115 being exploited? There is no known exploitation of CVE-2025-22115 in the wild and no public exploit code. ## Other vulnerabilities in Linux kernel - [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild) - [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild) - [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild) - [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild) - [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2025-22115 and fix it if it is affected. What it is: CVE-2025-22115 is a high-severity vulnerability in Linux kernel, published on 16 Apr 2025. It can only be exploited from the same machine or local network, with no action from the victim. Exploitation: There is no known exploitation of CVE-2025-22115 in the wild and no public exploit code. Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2025-22115/ (Markdown: https://insights.sbomify.com/CVE-2025-22115/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2025-22115 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-22115 - OSV: https://osv.dev/vulnerability/CVE-2025-22115 --- From sbomify Insights: https://insights.sbomify.com/CVE-2025-22115/ Summaries are generated and may contain mistakes; the official description above is the record.