CVE-2026-45892
ext4: drop extent cache after doing PARTIAL_VALID1 zeroout
In the Linux kernel, the following vulnerability has been resolved: ext4: drop extent cache after doing PARTIAL_VALID1 zeroout When splitting an unwritten extent in the middle and converting it to initialized in ext4_split_extent() with the EXT4_EXT_MAY_ZEROOUT and EXT4_EXT_DATA_VALID2 flags set, it could leave a stale unwritten extent. Assume we have an unwritten file and buffered write in the middle of it without dioread_nolock enabled, it will allocate blocks as written extent. 0 A B N [UUUUUUUUUUUU] on-disk extent U: unwritten extent [UUUUUUUUUUUU] extent status tree [--DDDDDDDD--] D: valid data |<- ->| ----> this range needs to be initialized ext4_split_extent() first try to split this extent at B with EXT4_EXT_DATA_PARTIAL_VALID1 and EXT4_EXT_MAY_ZEROOUT flag set, but ext4_split_extent_at() failed to split this extent due to temporary lack of space. It zeroout B to N and leave the entire extent as unwritten. 0 A B N [UUUUUUUUUUUU] on-disk extent [UUUUUUUUUUUU] extent status tree [--DDDDDDDDZZ] Z: zeroed data ext4_split_extent() then try to split this extent at A with EXT4_EXT_DATA_VALID2 flag set. This time, it split successfully and leave an written extent from A to N. 0 A B N [UUWWWWWWWWWW] on-disk extent W: written extent [UUUUUUUUUUUU] extent status tree [--DDDDDDDDZZ] Finally ext4_map_create_blocks() only insert extent A to B to the extent status tree, and leave an stale unwritten extent in the status tree. 0 A B N [UUWWWWWWWWWW] on-disk extent W: written extent [UUWWWWWWWWUU] extent status tree [--DDDDDDDDZZ] Fix this issue by always cached extent status entry after zeroing out the second part.
Fixes and workarounds
No remediation reported in collected sources.
Missing remediation information is not evidence that no patch exists.
Affected products and versions
| Product | Versions | Authority |
|---|---|---|
| Linux Linux |
≥ ddf854e59166533b0f46ba32cd6cd9aca3197d1b; < 28db4bfc6f82fd20e2aadb7fc162244109a4eb31 (affected, git) ≥ 58ddae5d77b1db3a27b891c75a8fa120239ac092; < f0931a5c17005a0c4fc35bd1a001245effc3354b (affected, git) ≥ d17857b4fb9ba5745b59be0ef38fd532991fccbf; < d8ee559fccdef713f058cfe5f2c03dc9b18be3b1 (affected, git) ≥ d67c8ecf3d8fda9b8ef80e6f665d84b6d6ac9d88; < c2ee51d684adca7645e4aa74adca13f6750390bc (affected, git) ≥ 7015fcf473796e1d2d876f241bd9e0c36f3d4eef; < a1b962a821e7a52d48212ae269b45808b4411267 (affected, git) ≥ 1bf6974822d1dba86cf11b5f05498581cf3488a2; < 6d882ea3b0931b43530d44149b79fcd4ffc13030 (affected, git) Other versions: unaffected |
CNA: Linux |
| Linux Linux |
≥ 6.1.167; < 6.1.168 (affected, semver)
Other versions: unaffected |
CNA: Linux |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
No CVSS assessment reported. An unscored record is not a low-severity determination.
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://git.kernel.org/stable/c/28db4bfc6f82fd20e2aadb7fc162244109a4eb31CNA: Linux
- https://git.kernel.org/stable/c/f0931a5c17005a0c4fc35bd1a001245effc3354bCNA: Linux
- https://git.kernel.org/stable/c/d8ee559fccdef713f058cfe5f2c03dc9b18be3b1CNA: Linux
- https://git.kernel.org/stable/c/c2ee51d684adca7645e4aa74adca13f6750390bcCNA: Linux
- https://git.kernel.org/stable/c/a1b962a821e7a52d48212ae269b45808b4411267CNA: Linux
- https://git.kernel.org/stable/c/6d882ea3b0931b43530d44149b79fcd4ffc13030CNA: Linux
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