CVE-2024-57952: Revert "libfs: fix infinite directory reads for offset dir"
First published: Wed Feb 12 2025(Updated: )
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.
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux Kernel | ||
| Linux Kernel | >=6.11<6.12.12 | |
| Linux Kernel | =6.13 | |
| Linux Kernel | =6.13-rc1 | |
| Linux Kernel | =6.13-rc2 | |
| Linux Kernel | =6.13-rc3 | |
| Linux Kernel | =6.13-rc4 | |
| Linux Kernel | =6.13-rc5 | |
| Linux Kernel | =6.13-rc6 | |
| Linux Kernel | =6.13-rc7 |
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Reference Links
Frequently Asked Questions
What is the severity of CVE-2024-57952?
CVE-2024-57952 has been classified with a moderate severity level due to potential risks associated with infinite directory reads.
How do I fix CVE-2024-57952?
To fix CVE-2024-57952, ensure that your Linux kernel is updated with the latest patches that address this vulnerability.
What systems are affected by CVE-2024-57952?
CVE-2024-57952 affects the Linux Kernel, particularly versions that include the vulnerable implementation of the directory offset allocator.
What potential impact does CVE-2024-57952 have on systems?
CVE-2024-57952 could lead to resource exhaustion due to infinite directory read operations, potentially disrupting normal system operations.
Is CVE-2024-57952 relevant for all Linux users?
Yes, CVE-2024-57952 is relevant for all Linux users as it impacts the underlying kernel functionality used by various applications.
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