CVE-2025-40167

Summary

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

ext4: detect invalid INLINE_DATA + EXTENTS flag combination

syzbot reported a BUG_ON in ext4_es_cache_extent() when opening a verity file on a corrupted ext4 filesystem mounted without a journal.

The issue is that the filesystem has an inode with both the INLINE_DATA and EXTENTS flags set:

EXT4-fs error (device loop0): ext4_cache_extents:545: inode #15:
comm syz.0.17: corrupted extent tree: lblk 0 < prev 66

Investigation revealed that the inode has both flags set: DEBUG: inode 15 - flag=1, i_inline_off=164, has_inline=1, extents_flag=1

This is an invalid combination since an inode should have either:

• INLINE_DATA: data stored directly in the inode
• EXTENTS: data stored in extent-mapped blocks

Having both flags causes ext4_has_inline_data() to return true, skipping extent tree validation in __ext4_iget(). The unvalidated out-of-order extents then trigger a BUG_ON in ext4_es_cache_extent() due to integer underflow when calculating hole sizes.

Fix this by detecting this invalid flag combination early in ext4_iget() and rejecting the corrupted inode.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/4954d297c91d292630ab43ba4d195dc371ce65d3
• https://git.kernel.org/stable/c/f061f7c331fc16250fc82aa68964f35821687217
• https://git.kernel.org/stable/c/2e9e10657b04152ed0d6ecae8d0c02a3405e28f5
• https://git.kernel.org/stable/c/1437c95ab2a28b138d4521653583729f61ccb48b
• https://git.kernel.org/stable/c/cb6039b68efa547b676a8a10fc4618d9d1865c23
• https://git.kernel.org/stable/c/de985264eef64be8a90595908f2e6a87946dad34
• https://git.kernel.org/stable/c/1f5ccd22ff482639133f2a0fe08f6d19d0e68717
• https://git.kernel.org/stable/c/1d3ad183943b38eec2acf72a0ae98e635dc8456b

• ←Previous
• Next→