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]

Weaknesses 1

Affected Products 15

References 6

• git.kernel.org https://git.kernel.org/stable/c/3a7667595bcad84da53fc156a418e110267c3412
  Patch
• git.kernel.org https://git.kernel.org/stable/c/416c86f30f91b4fb2642ef6b102596ca898f41a5
  Patch
• git.kernel.org https://git.kernel.org/stable/c/5422fe71d26d42af6c454ca9527faaad4e677d6c
  Patch
• git.kernel.org https://git.kernel.org/stable/c/64f425b06b3bea9abc8977fd3982779b3ad070c9
  Patch
• git.kernel.org https://git.kernel.org/stable/c/c66545e83a802c3851d9be27a41c0479dd29ff0c
  Patch
• git.kernel.org https://git.kernel.org/stable/c/ecc50bfca9b5c2ee6aeef998181689b80477367b
  Patch

Remediation

• git.kernel.org https://git.kernel.org/stable/c/3a7667595bcad84da53fc156a418e110267c3412
  Patch
• git.kernel.org https://git.kernel.org/stable/c/416c86f30f91b4fb2642ef6b102596ca898f41a5
  Patch
• git.kernel.org https://git.kernel.org/stable/c/5422fe71d26d42af6c454ca9527faaad4e677d6c
  Patch
• git.kernel.org https://git.kernel.org/stable/c/64f425b06b3bea9abc8977fd3982779b3ad070c9
  Patch
• git.kernel.org https://git.kernel.org/stable/c/c66545e83a802c3851d9be27a41c0479dd29ff0c
  Patch
• git.kernel.org https://git.kernel.org/stable/c/ecc50bfca9b5c2ee6aeef998181689b80477367b
  Patch