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Incorrect Calculation of Buffer Size Affecting kernel-debug-modules package, versions *

Severity

 Recommended
0.0
high
0
10

Based on CentOS security rating.

Threat Intelligence

EPSS
0.02% (7th percentile)

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  • Snyk IDSNYK-CENTOS10-KERNELDEBUGMODULES-16460071
  • published7 May 2026
  • disclosed6 May 2026
Report a new vulnerability Found a mistake?

Introduced: 6 May 2026

NewCVE-2026-43158  (opens in a new tab)
CWE-131  (opens in a new tab)

How to fix?

There is no fixed version for Centos:10 kernel-debug-modules.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-debug-modules package and not the kernel-debug-modules package as distributed by Centos. See How to fix? for Centos:10 relevant fixed versions and status.

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

xfs: fix freemap adjustments when adding xattrs to leaf blocks

xfs/592 and xfs/794 both trip this assertion in the leaf block freemap adjustment code after ~20 minutes of running on my test VMs:

ASSERT(ichdr->firstused >= ichdr->count * sizeof(xfs_attr_leaf_entry_t) + xfs_attr3_leaf_hdr_size(leaf));

Upon enabling quite a lot more debugging code, I narrowed this down to fsstress trying to set a local extended attribute with namelen=3 and valuelen=71. This results in an entry size of 80 bytes.

At the start of xfs_attr3_leaf_add_work, the freemap looks like this:

i 0 base 448 size 0 rhs 448 count 46 i 1 base 388 size 132 rhs 448 count 46 i 2 base 2120 size 4 rhs 448 count 46 firstused = 520

where "rhs" is the first byte past the end of the leaf entry array. This is inconsistent -- the entries array ends at byte 448, but freemap[1] says there's free space starting at byte 388!

By the end of the function, the freemap is in worse shape:

i 0 base 456 size 0 rhs 456 count 47 i 1 base 388 size 52 rhs 456 count 47 i 2 base 2120 size 4 rhs 456 count 47 firstused = 440

Important note: 388 is not aligned with the entries array element size of 8 bytes.

Based on the incorrect freemap, the name area starts at byte 440, which is below the end of the entries array! That's why the assertion triggers and the filesystem shuts down.

How did we end up here? First, recall from the previous patch that the freemap array in an xattr leaf block is not intended to be a comprehensive map of all free space in the leaf block. In other words, it's perfectly legal to have a leaf block with:

  • 376 bytes in use by the entries array
  • freemap[0] has [base = 376, size = 8]
  • freemap[1] has [base = 388, size = 1500]
  • the space between 376 and 388 is free, but the freemap stopped tracking that some time ago

If we add one xattr, the entries array grows to 384 bytes, and freemap[0] becomes [base = 384, size = 0]. So far, so good. But if we add a second xattr, the entries array grows to 392 bytes, and freemap[0] gets pushed up to [base = 392, size = 0]. This is bad, because freemap[1] hasn't been updated, and now the entries array and the free space claim the same space.

The fix here is to adjust all freemap entries so that none of them collide with the entries array. Note that this fix relies on commit 2a2b5932db6758 ("xfs: fix attr leaf header freemap.size underflow") and the previous patch that resets zero length freemap entries to have base = 0.

CVSS Base Scores

version 3.1