# CVE-2022-50021: ext4: block range must be validated before use in ext4_mb_clear_bb()

Status: published. Published: 2025-06-18. Updated: 2026-11-05.

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

ext4: block range must be validated before use in ext4_mb_clear_bb()

Block range to free is validated in ext4_free_blocks() using
ext4_inode_block_valid() and then it's passed to ext4_mb_clear_bb().
However in some situations on bigalloc file system the range might be
adjusted after the validation in ext4_free_blocks() which can lead to
troubles on corrupted file systems such as one found by syzkaller that
resulted in the following BUG

kernel BUG at fs/ext4/ext4.h:3319!
PREEMPT SMP NOPTI
CPU: 28 PID: 4243 Comm: repro Kdump: loaded Not tainted 5.19.0-rc6+ #1
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1.fc35 04/01/2014
RIP: 0010:ext4_free_blocks+0x95e/0xa90
Call Trace:
 <TASK>
 ? lock_timer_base+0x61/0x80
 ? __es_remove_extent+0x5a/0x760
 ? __mod_timer+0x256/0x380
 ? ext4_ind_truncate_ensure_credits+0x90/0x220
 ext4_clear_blocks+0x107/0x1b0
 ext4_free_data+0x15b/0x170
 ext4_ind_truncate+0x214/0x2c0
 ? _raw_spin_unlock+0x15/0x30
 ? ext4_discard_preallocations+0x15a/0x410
 ? ext4_journal_check_start+0xe/0x90
 ? __ext4_journal_start_sb+0x2f/0x110
 ext4_truncate+0x1b5/0x460
 ? __ext4_journal_start_sb+0x2f/0x110
 ext4_evict_inode+0x2b4/0x6f0
 evict+0xd0/0x1d0
 ext4_enable_quotas+0x11f/0x1f0
 ext4_orphan_cleanup+0x3de/0x430
 ? proc_create_seq_private+0x43/0x50
 ext4_fill_super+0x295f/0x3ae0
 ? snprintf+0x39/0x40
 ? sget_fc+0x19c/0x330
 ? ext4_reconfigure+0x850/0x850
 get_tree_bdev+0x16d/0x260
 vfs_get_tree+0x25/0xb0
 path_mount+0x431/0xa70
 __x64_sys_mount+0xe2/0x120
 do_syscall_64+0x5b/0x80
 ? do_user_addr_fault+0x1e2/0x670
 ? exc_page_fault+0x70/0x170
 entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7fdf4e512ace

Fix it by making sure that the block range is properly validated before
used every time it changes in ext4_free_blocks() or ext4_mb_clear_bb().

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 84130193e0e6568dfdfb823f0e1e19aec80aff6e; < 7550aade978371ac582f6d43b14c4cb89ca54463 (affected, git); ≥ 84130193e0e6568dfdfb823f0e1e19aec80aff6e; < 560a2744cbbf03cac65a6394f9b0d99aa437c867 (affected, git); ≥ 84130193e0e6568dfdfb823f0e1e19aec80aff6e; < a2522041d248a8c969cbbc97e1fc2cd8b4de120d (affected, git); ≥ 84130193e0e6568dfdfb823f0e1e19aec80aff6e; < 1e1c2b86ef86a8477fd9b9a4f48a6bfe235606f6 (affected, git). Source: CNA: Linux
- Linux / Linux: 3.2 (affected); ≥ 0; < 3.2 (unaffected, semver); ≥ 5.10.175; ≤ 5.10.* (unaffected, semver); ≥ 5.15.103; ≤ 5.15.* (unaffected, semver); ≥ 5.19.4; ≤ 5.19.* (unaffected, semver); ≥ 6.0; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.20% as of 2026-11-05; percentile 10.42%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/7550aade978371ac582f6d43b14c4cb89ca54463 (CNA: Linux)

- https://git.kernel.org/stable/c/560a2744cbbf03cac65a6394f9b0d99aa437c867 (CNA: Linux)

- https://git.kernel.org/stable/c/a2522041d248a8c969cbbc97e1fc2cd8b4de120d (CNA: Linux)

- https://git.kernel.org/stable/c/1e1c2b86ef86a8477fd9b9a4f48a6bfe235606f6 (CNA: Linux)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2022-50021; retrieved 2026-11-05; source updated 2026-11-05

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2022-50021; retrieved 2026-11-05; source updated Not reported

Revision: 3a7a883e4e8ae59252bdfb92c259437a645dcd8193981d1994b27cd20677378d

Canonical: https://y2.dev/cve/CVE-2022-50021

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