In the Linux kernel, the following vulnerability has been resolved: Revert "libfs: fix infinite directory reads for offset dir" The current directory offset allocator (based on mtree_alloc_cyclic) stores the next offset value to return in octx->next_offset. This mechanism typically returns values that increase monotonically over time. Eventually, though, the newly allocated offset value wraps back to a low number (say, 2) which is smaller than other already- allocated offset values. Yu Kuai <yukuai3@huawei.com> reports that, after commit 64a7ce76fb90 ("libfs: fix infinite directory reads for offset dir"), if a directory's offset allocator wraps, existing entries are no longer visible via readdir/getdents because offset_readdir() stops listing entries once an entry's offset is larger than octx->next_offset. These entries vanish persistently -- they can be looked up, but will never again appear in readdir(3) output. The reason for this is that the commit treats directory offsets as monotonically increasing integer values rather than opaque cookies, and introduces this comparison: if (dentry2offset(dentry) >= last_index) { On 64-bit platforms, the directory offset value upper bound is 2^63 - 1. Directory offsets will monotonically increase for millions of years without wrapping. On 32-bit platforms, however, LONG_MAX is 2^31 - 1. The allocator can wrap after only a few weeks (at worst). Revert commit 64a7ce76fb90 ("libfs: fix infinite directory reads for offset dir") to prepare for a fix that can work properly on 32-bit systems and might apply to recent LTS kernels where shmem employs the simple_offset mechanism.
History

Fri, 14 Feb 2025 16:15:00 +0000

Type Values Removed Values Added
First Time appeared Linux
Linux linux Kernel
Weaknesses NVD-CWE-noinfo
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.13:-:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.13:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.13:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.13:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.13:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.13:rc5:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.13:rc6:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.13:rc7:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
Metrics 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'}


Wed, 12 Feb 2025 14:00:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: Revert "libfs: fix infinite directory reads for offset dir" The current directory offset allocator (based on mtree_alloc_cyclic) stores the next offset value to return in octx->next_offset. This mechanism typically returns values that increase monotonically over time. Eventually, though, the newly allocated offset value wraps back to a low number (say, 2) which is smaller than other already- allocated offset values. Yu Kuai <yukuai3@huawei.com> reports that, after commit 64a7ce76fb90 ("libfs: fix infinite directory reads for offset dir"), if a directory's offset allocator wraps, existing entries are no longer visible via readdir/getdents because offset_readdir() stops listing entries once an entry's offset is larger than octx->next_offset. These entries vanish persistently -- they can be looked up, but will never again appear in readdir(3) output. The reason for this is that the commit treats directory offsets as monotonically increasing integer values rather than opaque cookies, and introduces this comparison: if (dentry2offset(dentry) >= last_index) { On 64-bit platforms, the directory offset value upper bound is 2^63 - 1. Directory offsets will monotonically increase for millions of years without wrapping. On 32-bit platforms, however, LONG_MAX is 2^31 - 1. The allocator can wrap after only a few weeks (at worst). Revert commit 64a7ce76fb90 ("libfs: fix infinite directory reads for offset dir") to prepare for a fix that can work properly on 32-bit systems and might apply to recent LTS kernels where shmem employs the simple_offset mechanism.
Title Revert "libfs: fix infinite directory reads for offset dir"
References

cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2025-02-13T15:37:47.855Z

Reserved: 2025-01-19T11:50:08.381Z

Link: CVE-2024-57952

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Analyzed

Published: 2025-02-12T14:15:31.540

Modified: 2025-02-14T15:52:04.957

Link: CVE-2024-57952

cve-icon Redhat

No data.