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CVE-2026-45858

ext4: don't zero the entire extent if EXT4_EXT_DATA_PARTIAL_VALID1 PUBLISHED

Description (CNA)

In the Linux kernel, the following vulnerability has been resolved: ext4: don't zero the entire extent if EXT4_EXT_DATA_PARTIAL_VALID1 When allocating initialized blocks from a large unwritten extent, or when splitting an unwritten extent during end I/O and converting it to initialized, there is currently a potential issue of stale data if the extent needs to be split in the middle. 0 A B N [UUUUUUUUUUUU] U: unwritten extent [--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_ENTIRE_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 mark the entire extent from 0 to N as written. 0 A B N [WWWWWWWWWWWW] W: written extent [SSDDDDDDDDZZ] Z: zeroed, S: stale 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 left a stale written extent from 0 to A. 0 A B N [WW|WWWWWWWWWW] [SS|DDDDDDDDZZ] Fix this by pass EXT4_EXT_DATA_PARTIAL_VALID1 to ext4_split_extent_at() when splitting at B, don't convert the entire extent to written and left it as unwritten after zeroing out B to N. The remaining work is just like the standard two-part split. ext4_split_extent() will pass the EXT4_EXT_DATA_VALID2 flag when it calls ext4_split_extent_at() for the second time, allowing it to properly handle the split. If the split is successful, it will keep extent from 0 to A as unwritten.

Affected (CNA)

Vendor / productVersions
Linux / Linuxaffected dee1f973ca341c266229faa5a1a5bb268bed3531 before 58ddae5d77b1db3a27b891c75a8fa120239ac092; affected dee1f973ca341c266229faa5a1a5bb268bed3531 before d17857b4fb9ba5745b59be0ef38fd532991fccbf; affected dee1f973ca341c266229faa5a1a5bb268bed3531 before d67c8ecf3d8fda9b8ef80e6f665d84b6d6ac9d88; affected dee1f973ca341c266229faa5a1a5bb268bed3531 before 7015fcf473796e1d2d876f241bd9e0c36f3d4eef; affected dee1f973ca341c266229faa5a1a5bb268bed3531 before 1bf6974822d1dba86cf11b5f05498581cf3488a2; affected 814a7833df19e1de7447f870ae890adb12561627; affected 4319fd00002630a761fa5559a086f11ed7623006; affected e28b27be06c5e6a5236c0c0b370ca0768ab086bb; affected 3.2.33 before 3.3; affected 3.4.16 before 3.5; affected 3.6.4 before 3.7
Linux / Linuxaffected 3.7; unaffected 0 before 3.7; unaffected 6.6.130 through 6.6.*; unaffected 6.12.75 through 6.12.*; unaffected 6.18.14 through 6.18.*; unaffected 6.19.4 through 6.19.*; unaffected 7.0 through *

CWE

No CWE identifiers supplied.

References