CVE-2026-31448 (GCVE-0-2026-31448)
Vulnerability from cvelistv5
Published
2026-04-22 13:53
Modified
2026-04-27 14:03
Severity ?
9.4 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H
Summary
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]
References
Impacted products
Vendor Product Version
Linux Linux Version: 315054f023d28ee64f308adf8b5737831541776b
Version: 315054f023d28ee64f308adf8b5737831541776b
Version: 315054f023d28ee64f308adf8b5737831541776b
Version: 315054f023d28ee64f308adf8b5737831541776b
Version: 315054f023d28ee64f308adf8b5737831541776b
Version: 315054f023d28ee64f308adf8b5737831541776b
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{
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: avoid infinite loops caused by residual data\n\nOn the mkdir/mknod path, when mapping logical blocks to physical blocks,\nif inserting a new extent into the extent tree fails (in this example,\nbecause the file system disabled the huge file feature when marking the\ninode as dirty), ext4_ext_map_blocks() only calls ext4_free_blocks() to\nreclaim the physical block without deleting the corresponding data in\nthe extent tree. This causes subsequent mkdir operations to reference\nthe previously reclaimed physical block number again, even though this\nphysical block is already being used by the xattr block. Therefore, a\nsituation arises where both the directory and xattr are using the same\nbuffer head block in memory simultaneously.\n\nThe above causes ext4_xattr_block_set() to enter an infinite loop about\n\"inserted\" and cannot release the inode lock, ultimately leading to the\n143s blocking problem mentioned in [1].\n\nIf the metadata is corrupted, then trying to remove some extent space\ncan do even more harm. Also in case EXT4_GET_BLOCKS_DELALLOC_RESERVE\nwas passed, remove space wrongly update quota information.\nJan Kara suggests distinguishing between two cases:\n\n1) The error is ENOSPC or EDQUOT - in this case the filesystem is fully\nconsistent and we must maintain its consistency including all the\naccounting. However these errors can happen only early before we\u0027ve\ninserted the extent into the extent tree. So current code works correctly\nfor this case.\n\n2) Some other error - this means metadata is corrupted. We should strive to\ndo as few modifications as possible to limit damage. So I\u0027d just skip\nfreeing of allocated blocks.\n\n[1]\nINFO: task syz.0.17:5995 blocked for more than 143 seconds.\nCall Trace:\n inode_lock_nested include/linux/fs.h:1073 [inline]\n __start_dirop fs/namei.c:2923 [inline]\n start_dirop fs/namei.c:2934 [inline]"
        }
      ],
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            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H",
            "version": "3.1"
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      "providerMetadata": {
        "dateUpdated": "2026-04-27T14:03:13.864Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/c66545e83a802c3851d9be27a41c0479dd29ff0c"
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          "url": "https://git.kernel.org/stable/c/ecc50bfca9b5c2ee6aeef998181689b80477367b"
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          "url": "https://git.kernel.org/stable/c/416c86f30f91b4fb2642ef6b102596ca898f41a5"
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        {
          "url": "https://git.kernel.org/stable/c/5422fe71d26d42af6c454ca9527faaad4e677d6c"
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      ],
      "title": "ext4: avoid infinite loops caused by residual data",
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  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31448",
    "datePublished": "2026-04-22T13:53:44.129Z",
    "dateReserved": "2026-03-09T15:48:24.091Z",
    "dateUpdated": "2026-04-27T14:03:13.864Z",
    "state": "PUBLISHED"
  },
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}


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