CVE-2026-43068: ext4: avoid allocate block from corrupted group in ext4_mb_find_by_goal()

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

ext4: avoid allocate block from corrupted group in ext4mbfindbygoal()

There's issue as follows: ... EXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 206 at logical offset 0 with max blocks 1 with error 117 EXT4-fs (mmcblk0p1): This should not happen!! Data will be lost

EXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 206 at logical offset 0 with max blocks 1 with error 117 EXT4-fs (mmcblk0p1): This should not happen!! Data will be lost

EXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 206 at logical offset 0 with max blocks 1 with error 117 EXT4-fs (mmcblk0p1): This should not happen!! Data will be lost

EXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 206 at logical offset 0 with max blocks 1 with error 117 EXT4-fs (mmcblk0p1): This should not happen!! Data will be lost

EXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 2243 at logical offset 0 with max blocks 1 with error 117 EXT4-fs (mmcblk0p1): This should not happen!! Data will be lost

EXT4-fs (mmcblk0p1): Delayed block allocation failed for inode 2239 at logical offset 0 with max blocks 1 with error 117 EXT4-fs (mmcblk0p1): This should not happen!! Data will be lost

EXT4-fs (mmcblk0p1): error count since last fsck: 1 EXT4-fs (mmcblk0p1): initial error at time 1765597433: ext4mbgeneratebuddy:760 EXT4-fs (mmcblk0p1): last error at time 1765597433: ext4mbgeneratebuddy:760 ...

According to the log analysis, blocks are always requested from the corrupted block group. This may happen as follows: ext4mbfindbygoal ext4mbloadbuddy ext4mbloadbuddygfp ext4mbinitcache ext4readblockbitmapnowait ext4waitblockbitmap ext4validateblockbitmap if (!grp || EXT4MBGRPBBITMAPCORRUPT(grp)) return -EFSCORRUPTED; // There's no logs. if (err) return err; // Will return error ext4lockgroup(ac->acsb, group); if (unlikely(EXT4MBGRPBBITMAPCORRUPT(e4b->bdinfo))) // Unreachable goto out;

After commit 9008a58e5dce ("ext4: make the bitmap read routines return real error codes") merged, Commit 163a203ddb36 ("ext4: mark block group as corrupt on block bitmap error") is no real solution for allocating blocks from corrupted block groups. This is because if 'EXT4MBGRPBBITMAPCORRUPT(e4b->bdinfo)' is true, then 'ext4mbloadbuddy()' may return an error. This means that the block allocation will fail. Therefore, check block group if corrupted when ext4mbloadbuddy() returns error.