CVE-2026-53040

ocfs2: validate bg_bits during freefrag scan

State: Published
Severity: 7.1 High
Published: Jun 24, 2026
Updated: Aug 5, 2026
Reserved: Jun 9, 2026

Description

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.

Scores

CVSS	Score	Vector	Source
3.1	7.1 High	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H	Linux

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before bb2906a1065ec28de021bac2ed03f2624edd7d07Affected d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before 3e167e230d19cd273108bab2e4c61800fc335ae8Affected d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before 0998674eec138c55e9e349b9cbd9dbc5129a9cc8Affected d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before bb3c54d1e71578521111f1a1ee7d5f4761a242b8Affected d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before 05d0cbea41167b6b061c6ba5b70ee5a9a7a24c9eAffected d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before 4c2d62ddde8928db12f4608950b67a20e67deab2Affected d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before e0dcf12665d6dde37facf790803cdad44d5c328cAffected d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before 8f687eeed3da3012152b0f9473f578869de0cd7bAffected
LinuxLinux	3.0Affected before 3.0Not affected 5.10.258 through 5.10.Not affected 5.15.209 through 5.15.Not affected 6.1.175 through 6.1.Not affected 6.6.141 through 6.6.Not affected 6.12.91 through 6.12.Not affected 6.18.33 through 6.18.Not affected 7.0.10 through 7.0.*Not affected 7.1 and laterNot affected

Product

Versions

LinuxLinux

d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before bb2906a1065ec28de021bac2ed03f2624edd7d07Affected
d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before 3e167e230d19cd273108bab2e4c61800fc335ae8Affected
d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before 0998674eec138c55e9e349b9cbd9dbc5129a9cc8Affected
d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before bb3c54d1e71578521111f1a1ee7d5f4761a242b8Affected
d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before 05d0cbea41167b6b061c6ba5b70ee5a9a7a24c9eAffected
d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before 4c2d62ddde8928db12f4608950b67a20e67deab2Affected
d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before e0dcf12665d6dde37facf790803cdad44d5c328cAffected
d24a10b9f8ed548981696cd36e2b4f16e6f360b1 to before 8f687eeed3da3012152b0f9473f578869de0cd7bAffected

LinuxLinux

3.0Affected
before 3.0Not affected
5.10.258 through 5.10.*Not affected
5.15.209 through 5.15.*Not affected
6.1.175 through 6.1.*Not affected
6.6.141 through 6.6.*Not affected
6.12.91 through 6.12.*Not affected
6.18.33 through 6.18.*Not affected
7.0.10 through 7.0.*Not affected
7.1 and laterNot affected

References

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