High 7.1Published Jun 24, 2026

CVE-2026-53040ocfs2: validate bg_bits during freefrag scan

Updated under an hour ago (Oct 28, 2026, 3:10 PM ET)

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In the Linux kernel, the following vulnerability has been resolved: ocfs2: validate bg_bits during freefrag scan [BUG] A crafted filesystem can trigger an out-of-bounds bitmap walk when OCFS2_IOC_INFO is issued with OCFS2_INFO_FL_NON_COHERENT. BUG: KASAN: use-after-free in instrument_atomic_read include/linux/instrumented.h:68 [inline] BUG: KASAN: use-after-free in _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] BUG: KASAN: use-after-free in test_bit_le include/asm-generic/bitops/le.h:21 [inline] BUG: KASAN: use-after-free in ocfs2_info_freefrag_scan_chain fs/ocfs2/ioctl.c:495 [inline] BUG: KASAN: use-after-free in ocfs2_info_freefrag_scan_bitmap fs/ocfs2/ioctl.c:588 [inline] BUG: KASAN: use-after-free in ocfs2_info_handle_freefrag fs/ocfs2/ioctl.c:662 [inline] BUG: KASAN: use-after-free in ocfs2_info_handle_request+0x1c66/0x3370 fs/ocfs2/ioctl.c:754 Read of size 8 at addr ffff888031bce000 by task syz.0.636/1435 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0xbe/0x130 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xd1/0x650 mm/kasan/report.c:482 kasan_report+0xfb/0x140 mm/kasan/report.c:595 check_region_inline mm/kasan/generic.c:186 [inline] kasan_check_range+0x11c/0x200 mm/kasan/generic.c:200 __kasan_check_read+0x11/0x20 mm/kasan/shadow.c:31 instrument_atomic_read include/linux/instrumented.h:68 [inline] _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] test_bit_le include/asm-generic/bitops/le.h:21 [inline] ocfs2_info_freefrag_scan_chain fs/ocfs2/ioctl.c:495 [inline] ocfs2_info_freefrag_scan_bitmap fs/ocfs2/ioctl.c:588 [inline] ocfs2_info_handle_freefrag fs/ocfs2/ioctl.c:662 [inline] ocfs2_info_handle_request+0x1c66/0x3370 fs/ocfs2/ioctl.c:754 ocfs2_info_handle+0x18d/0x2a0 fs/ocfs2/ioctl.c:828 ocfs2_ioctl+0x632/0x6e0 fs/ocfs2/ioctl.c:913 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl fs/ioctl.c:583 [inline] __x64_sys_ioctl+0x197/0x1e0 fs/ioctl.c:583 ... [CAUSE] ocfs2_info_freefrag_scan_chain() uses on-disk bg_bits directly as the bitmap scan limit. The coherent path reads group descriptors through ocfs2_read_group_descriptor(), which validates the descriptor before use. The non-coherent path uses ocfs2_read_blocks_sync() instead and skips that validation, so an impossible bg_bits value can drive the bitmap walk past the end of the block. [FIX] Compute the bitmap capacity from the filesystem format with ocfs2_group_bitmap_size(), report descriptors whose bg_bits exceeds that limit, and clamp the scan to the computed capacity. This keeps the freefrag report going while avoiding reads beyond the buffer.

CVSS: 7.1 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Weakness (CWE): Not given
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Analyzed
Record last updated: Aug 5, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from d24a10b9f8ed548981696cd36e2b4f16e6f360b1 before bb2906a1065ec28de021bac2ed03f2624edd7d07; from d24a10b9f8ed548981696cd36e2b4f16e6f360b1 before 3e167e230d19cd273108bab2e4c61800fc335ae8; from d24a10b9f8ed548981696cd36e2b4f16e6f360b1 before 0998674eec138c55e9e349b9cbd9dbc5129a9cc8; from d24a10b9f8ed548981696cd36e2b4f16e6f360b1 before bb3c54d1e71578521111f1a1ee7d5f4761a242b8; from d24a10b9f8ed548981696cd36e2b4f16e6f360b1 before 05d0cbea41167b6b061c6ba5b70ee5a9a7a24c9e; from d24a10b9f8ed548981696cd36e2b4f16e6f360b1 before 4c2d62ddde8928db12f4608950b67a20e67deab2; from d24a10b9f8ed548981696cd36e2b4f16e6f360b1 before e0dcf12665d6dde37facf790803cdad44d5c328c; from d24a10b9f8ed548981696cd36e2b4f16e6f360b1 before 8f687eeed3da3012152b0f9473f578869de0cd7b	CNA record
linux linux_kernel linux:linux_kernel	from 3.0 before 5.10.258; from 5.11 before 5.15.209; from 5.16 before 6.1.175; from 6.2 before 6.6.141; from 6.7 before 6.12.91; from 6.13 before 6.18.33; from 6.19 before 7.0.10	NVD

References

References

https://git.kernel.org/stable/c/bb2906a1065ec28de021bac2ed03f2624edd7d07	patch
https://git.kernel.org/stable/c/3e167e230d19cd273108bab2e4c61800fc335ae8	patch
https://git.kernel.org/stable/c/0998674eec138c55e9e349b9cbd9dbc5129a9cc8	patch
https://git.kernel.org/stable/c/bb3c54d1e71578521111f1a1ee7d5f4761a242b8	patch
https://git.kernel.org/stable/c/05d0cbea41167b6b061c6ba5b70ee5a9a7a24c9e	patch
https://git.kernel.org/stable/c/4c2d62ddde8928db12f4608950b67a20e67deab2	patch
https://git.kernel.org/stable/c/e0dcf12665d6dde37facf790803cdad44d5c328c	patch
https://git.kernel.org/stable/c/8f687eeed3da3012152b0f9473f578869de0cd7b	patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.