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CVE PROGRAM SOURCE RECORD9.4 Critical

CVE-2026-31448

ext4: avoid infinite loops caused by residual data

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In the Linux kernel, the following vulnerability has been resolved: ext4: avoid infinite loops caused by residual data On the mkdir/mknod path, when mapping logical blocks to physical blocks, if inserting a new extent into the extent tree fails (in this example, because the file system disabled the huge file feature when marking the inode as dirty), ext4_ext_map_blocks() only calls ext4_free_blocks() to reclaim the physical block without deleting the corresponding data in the extent tree. This causes subsequent mkdir operations to reference the previously reclaimed physical block number again, even though this physical block is already being used by the xattr block. Therefore, a situation arises where both the directory and xattr are using the same buffer head block in memory simultaneously. The above causes ext4_xattr_block_set() to enter an infinite loop about "inserted" and cannot release the inode lock, ultimately leading to the 143s blocking problem mentioned in [1]. If the metadata is corrupted, then trying to remove some extent space can do even more harm. Also in case EXT4_GET_BLOCKS_DELALLOC_RESERVE was passed, remove space wrongly update quota information. Jan Kara suggests distinguishing between two cases: 1) The error is ENOSPC or EDQUOT - in this case the filesystem is fully consistent and we must maintain its consistency including all the accounting. However these errors can happen only early before we've inserted the extent into the extent tree. So current code works correctly for this case. 2) Some other error - this means metadata is corrupted. We should strive to do as few modifications as possible to limit damage. So I'd just skip freeing of allocated blocks. [1] INFO: task syz.0.17:5995 blocked for more than 143 seconds. Call Trace: inode_lock_nested include/linux/fs.h:1073 [inline] __start_dirop fs/namei.c:2923 [inline] start_dirop fs/namei.c:2934 [inline]

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 315054f023d28ee64f308adf8b5737831541776b to < c66545e83a802c3851d9be27a41c0479dd29ff0caffected
  • 315054f023d28ee64f308adf8b5737831541776b to < ecc50bfca9b5c2ee6aeef998181689b80477367baffected
  • 315054f023d28ee64f308adf8b5737831541776b to < 3a7667595bcad84da53fc156a418e110267c3412affected
  • 315054f023d28ee64f308adf8b5737831541776b to < 416c86f30f91b4fb2642ef6b102596ca898f41a5affected
  • 315054f023d28ee64f308adf8b5737831541776b to < 64f425b06b3bea9abc8977fd3982779b3ad070c9affected
  • 315054f023d28ee64f308adf8b5737831541776b to < 5422fe71d26d42af6c454ca9527faaad4e677d6caffected

Linux Linux

Default version status: affected

  • 2.6.22affected
  • 0 to < 2.6.22unaffected
  • 6.1.168 to ≤ 6.1.*unaffected
  • 6.6.131 to ≤ 6.6.*unaffected
  • 6.12.80 to ≤ 6.12.*unaffected
  • 6.18.21 to ≤ 6.18.*unaffected
  • 6.19.11 to ≤ 6.19.*unaffected
  • 7.0 to ≤ *unaffected

References