CVE-2026-97416 (GCVE-0-2026-97416)
Vulnerability from cvelistv5
Published
2026-09-24 16:03
Modified
2026-10-03 10:58
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: balance: fix potential bg lookup failure in btrfs_may_alloc_data_chunk() [BUG] Running btrfs balance can trigger a null-ptr-deref before relocating a data chunk when metadata corruption leaves a chunk in the chunk tree without a corresponding block group in the in-memory cache: KASAN: null-ptr-deref in range [0x0000000000000088-0x000000000000008f] RIP: 0010:btrfs_may_alloc_data_chunk+0x40/0x1c0 fs/btrfs/volumes.c:3601 Call Trace: __btrfs_balance fs/btrfs/volumes.c:4217 [inline] btrfs_balance+0x2516/0x42b0 fs/btrfs/volumes.c:4604 btrfs_ioctl_balance fs/btrfs/ioctl.c:3577 [inline] btrfs_ioctl+0x25cf/0x5b90 fs/btrfs/ioctl.c:5313 ... [CAUSE] __btrfs_balance() iterates the on-disk chunk tree and passes the chunk logical bytenr to btrfs_may_alloc_data_chunk() before relocating a data chunk. That helper then queries the in-memory block group cache: cache = btrfs_lookup_block_group(fs_info, chunk_offset); chunk_type = cache->flags; /* cache may be NULL */ A corrupt image can contain a chunk item whose matching block group item is missing, so no block group is ever inserted into the cache. In that case btrfs_lookup_block_group() returns NULL. The code only guards this with ASSERT(cache), which becomes a no-op when CONFIG_BTRFS_ASSERT is disabled. The subsequent dereference of cache->flags therefore crashes the kernel. [FIX] Add a NULL check after btrfs_lookup_block_group() in btrfs_may_alloc_data_chunk() and print and error message for clarity.
References
Impacted products
Vendor Product Version
Linux Linux Version: a6f93c71d412ba8ed743152c3a54ad0b78dcd9c7
Version: a6f93c71d412ba8ed743152c3a54ad0b78dcd9c7
Version: a6f93c71d412ba8ed743152c3a54ad0b78dcd9c7
Version: a6f93c71d412ba8ed743152c3a54ad0b78dcd9c7
Version: a6f93c71d412ba8ed743152c3a54ad0b78dcd9c7
Version: a6f93c71d412ba8ed743152c3a54ad0b78dcd9c7
Version: a6f93c71d412ba8ed743152c3a54ad0b78dcd9c7
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/btrfs/volumes.c"
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            },
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              "version": "6.1.189",
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            },
            {
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              "status": "unaffected",
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              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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              "negate": false,
              "operator": "OR"
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: balance: fix potential bg lookup failure in btrfs_may_alloc_data_chunk()\n\n[BUG]\nRunning btrfs balance can trigger a null-ptr-deref before relocating a\ndata chunk when metadata corruption leaves a chunk in the chunk tree\nwithout a corresponding block group in the in-memory cache:\n\n  KASAN: null-ptr-deref in range [0x0000000000000088-0x000000000000008f]\n  RIP: 0010:btrfs_may_alloc_data_chunk+0x40/0x1c0 fs/btrfs/volumes.c:3601\n  Call Trace:\n    __btrfs_balance fs/btrfs/volumes.c:4217 [inline]\n    btrfs_balance+0x2516/0x42b0 fs/btrfs/volumes.c:4604\n    btrfs_ioctl_balance fs/btrfs/ioctl.c:3577 [inline]\n    btrfs_ioctl+0x25cf/0x5b90 fs/btrfs/ioctl.c:5313\n    ...\n\n[CAUSE]\n__btrfs_balance() iterates the on-disk chunk tree and passes the chunk\nlogical bytenr to btrfs_may_alloc_data_chunk() before relocating a data\nchunk. That helper then queries the in-memory block group cache:\n\n  cache = btrfs_lookup_block_group(fs_info, chunk_offset);\n  chunk_type = cache-\u003eflags;   /* cache may be NULL */\n\nA corrupt image can contain a chunk item whose matching block group\nitem is missing, so no block group is ever inserted into the cache. In\nthat case btrfs_lookup_block_group() returns NULL.\n\nThe code only guards this with ASSERT(cache), which becomes a no-op when\nCONFIG_BTRFS_ASSERT is disabled. The subsequent dereference of\ncache-\u003eflags therefore crashes the kernel.\n\n[FIX]\nAdd a NULL check after btrfs_lookup_block_group() in\nbtrfs_may_alloc_data_chunk() and print and error message for clarity."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-03T10:58:07.862Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/9f37a6d6ae9e998232e2ba091ab4999cdf967e1b"
        },
        {
          "url": "https://git.kernel.org/stable/c/e479236a8f4d85c4fb6b3f7c2556c21f583e2bf2"
        },
        {
          "url": "https://git.kernel.org/stable/c/322f891b4d4fe64acb3351a0ffa62a7fa5ba7256"
        },
        {
          "url": "https://git.kernel.org/stable/c/81a664ed8b1a44c76b204c4bd0d751317a02c5cd"
        },
        {
          "url": "https://git.kernel.org/stable/c/9740dd0c17a4be8cc47a06c5ca5293471a7e286e"
        },
        {
          "url": "https://git.kernel.org/stable/c/59f75e0c8724d4adebc08c7dd3ff2358b80c21f7"
        },
        {
          "url": "https://git.kernel.org/stable/c/18d32b0013efba19f7ad3e5b08d7aee813d604a6"
        }
      ],
      "title": "btrfs: balance: fix potential bg lookup failure in btrfs_may_alloc_data_chunk()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-97416",
    "datePublished": "2026-09-24T16:03:23.731Z",
    "dateReserved": "2026-09-24T14:53:16.867Z",
    "dateUpdated": "2026-10-03T10:58:07.862Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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