CVE-2026-74571 (GCVE-0-2026-74571)
Vulnerability from cvelistv5
Published
2026-08-15 12:28
Modified
2026-08-17 05:22
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: skip global block reserve accounting for rescue mounts [BUG] Mounting with rescue=ibadroots after corrupting the block group tree root triggers a NULL pointer dereference: BUG: kernel NULL pointer dereference, address: 0000000000000100 RIP: 0010:btrfs_update_global_block_rsv+0x9d/0x1c0 [btrfs] Call Trace: fill_dummy_bgs+0xd4/0x120 [btrfs] open_ctree+0xc6e/0x1ca0 [btrfs] btrfs_get_tree+0x50d/0xa40 [btrfs] The same crash occurs with a corrupted raid stripe tree root, via btrfs_read_block_groups() instead of fill_dummy_bgs(). [CAUSE] With rescue=ibadroots, btrfs_read_roots() allows the mount to continue when either root cannot be read, leaving the corresponding root pointer NULL while its on-disk feature bit remains set. btrfs_update_global_block_rsv() then dereferences the missing root based on the feature bit alone. [FIX] Rescue mounts are fully read-only and cannot start transactions, so the global reserve is never consumed. Under btrfs_is_full_ro(), mark the reserve as full and return before performing the accounting. And since we need to check if the fs is mount fully RO, export fs_is_full_ro() as btrfs_is_full_ro(), and move it to fs.h. [ Squash the fs_is_full_ro() export commit into this one. ]
References
Impacted products
Vendor Product Version
Linux Linux Version: 8dbfc14fc736eb701089aff09645c3d4ad3decb1
Version: 8dbfc14fc736eb701089aff09645c3d4ad3decb1
Version: cbec34d3021d47007a0334c634f7053dbaf93d02
Version: 1e8087589b5cf6fa17adaf57b64cf1656d77dfec
Version: 6.1.43   ≤
Version: 6.4.8   ≤
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/btrfs/block-rsv.c",
            "fs/btrfs/disk-io.c",
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          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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          "versions": [
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            "fs/btrfs/disk-io.c",
            "fs/btrfs/fs.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
              "version": "6.5"
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              "versionType": "semver"
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              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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              "cpeMatch": [
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                  "versionStartIncluding": "6.5",
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                },
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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: skip global block reserve accounting for rescue mounts\n\n[BUG]\nMounting with rescue=ibadroots after corrupting the block group tree\nroot triggers a NULL pointer dereference:\n\n  BUG: kernel NULL pointer dereference, address: 0000000000000100\n  RIP: 0010:btrfs_update_global_block_rsv+0x9d/0x1c0 [btrfs]\n  Call Trace:\n   fill_dummy_bgs+0xd4/0x120 [btrfs]\n   open_ctree+0xc6e/0x1ca0 [btrfs]\n   btrfs_get_tree+0x50d/0xa40 [btrfs]\n\nThe same crash occurs with a corrupted raid stripe tree root, via\nbtrfs_read_block_groups() instead of fill_dummy_bgs().\n\n[CAUSE]\nWith rescue=ibadroots, btrfs_read_roots() allows the mount to continue\nwhen either root cannot be read, leaving the corresponding root pointer\nNULL while its on-disk feature bit remains set.\n\nbtrfs_update_global_block_rsv() then dereferences the missing root based\non the feature bit alone.\n\n[FIX]\nRescue mounts are fully read-only and cannot start transactions, so the\nglobal reserve is never consumed. Under btrfs_is_full_ro(), mark the\nreserve as full and return before performing the accounting.\n\nAnd since we need to check if the fs is mount fully RO, export\nfs_is_full_ro() as btrfs_is_full_ro(), and move it to fs.h.\n\n[ Squash the fs_is_full_ro() export commit into this one. ]"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:22:00.523Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/076349e4c8d11f6b58c4549976a513b2b4dc6df2"
        },
        {
          "url": "https://git.kernel.org/stable/c/51a0e8399858621442807a26057bcd1cd3ced046"
        }
      ],
      "title": "btrfs: skip global block reserve accounting for rescue mounts",
      "x_generator": {
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      }
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  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74571",
    "datePublished": "2026-08-15T12:28:10.711Z",
    "dateReserved": "2026-08-15T05:44:03.917Z",
    "dateUpdated": "2026-08-17T05:22:00.523Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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