CVE-2024-49868 (GCVE-0-2024-49868)

Vulnerability from cvelistv5 – Published: 2024-10-21 18:01 – Updated: 2026-01-05 10:54
VLAI?
Title
btrfs: fix a NULL pointer dereference when failed to start a new trasacntion
Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix a NULL pointer dereference when failed to start a new trasacntion [BUG] Syzbot reported a NULL pointer dereference with the following crash: FAULT_INJECTION: forcing a failure. start_transaction+0x830/0x1670 fs/btrfs/transaction.c:676 prepare_to_relocate+0x31f/0x4c0 fs/btrfs/relocation.c:3642 relocate_block_group+0x169/0xd20 fs/btrfs/relocation.c:3678 ... BTRFS info (device loop0): balance: ended with status: -12 Oops: general protection fault, probably for non-canonical address 0xdffffc00000000cc: 0000 [#1] PREEMPT SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000660-0x0000000000000667] RIP: 0010:btrfs_update_reloc_root+0x362/0xa80 fs/btrfs/relocation.c:926 Call Trace: <TASK> commit_fs_roots+0x2ee/0x720 fs/btrfs/transaction.c:1496 btrfs_commit_transaction+0xfaf/0x3740 fs/btrfs/transaction.c:2430 del_balance_item fs/btrfs/volumes.c:3678 [inline] reset_balance_state+0x25e/0x3c0 fs/btrfs/volumes.c:3742 btrfs_balance+0xead/0x10c0 fs/btrfs/volumes.c:4574 btrfs_ioctl_balance+0x493/0x7c0 fs/btrfs/ioctl.c:3673 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f [CAUSE] The allocation failure happens at the start_transaction() inside prepare_to_relocate(), and during the error handling we call unset_reloc_control(), which makes fs_info->balance_ctl to be NULL. Then we continue the error path cleanup in btrfs_balance() by calling reset_balance_state() which will call del_balance_item() to fully delete the balance item in the root tree. However during the small window between set_reloc_contrl() and unset_reloc_control(), we can have a subvolume tree update and created a reloc_root for that subvolume. Then we go into the final btrfs_commit_transaction() of del_balance_item(), and into btrfs_update_reloc_root() inside commit_fs_roots(). That function checks if fs_info->reloc_ctl is in the merge_reloc_tree stage, but since fs_info->reloc_ctl is NULL, it results a NULL pointer dereference. [FIX] Just add extra check on fs_info->reloc_ctl inside btrfs_update_reloc_root(), before checking fs_info->reloc_ctl->merge_reloc_tree. That DEAD_RELOC_TREE handling is to prevent further modification to the reloc tree during merge stage, but since there is no reloc_ctl at all, we do not need to bother that.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 3fd0a5585eb98e074fb9934549c8d85c49756c0d , < 1282f001cbf56e5dd6e90a18e205a566793f4be0 (git)
Affected: 3fd0a5585eb98e074fb9934549c8d85c49756c0d , < d73d48acf36f57362df7e4f9d76568168bf5e944 (git)
Affected: 3fd0a5585eb98e074fb9934549c8d85c49756c0d , < 37fee9c220b92c3b7bf22b51c51dde5364e7590b (git)
Affected: 3fd0a5585eb98e074fb9934549c8d85c49756c0d , < d13249c0df7aab885acb149695f82c54c0822a70 (git)
Affected: 3fd0a5585eb98e074fb9934549c8d85c49756c0d , < 7ad0c5868f2f0418619089513d95230c66cb7eb4 (git)
Affected: 3fd0a5585eb98e074fb9934549c8d85c49756c0d , < dc02c1440705e3451abd1c2c8114a5c1bb188e9f (git)
Affected: 3fd0a5585eb98e074fb9934549c8d85c49756c0d , < 39356ec0e319ed07627b3a0f402d0608546509e6 (git)
Affected: 3fd0a5585eb98e074fb9934549c8d85c49756c0d , < c3b47f49e83197e8dffd023ec568403bcdbb774b (git)
Create a notification for this product.
    Linux Linux Affected: 2.6.35
Unaffected: 0 , < 2.6.35 (semver)
Unaffected: 5.4.285 , ≤ 5.4.* (semver)
Unaffected: 5.10.227 , ≤ 5.10.* (semver)
Unaffected: 5.15.168 , ≤ 5.15.* (semver)
Unaffected: 6.1.113 , ≤ 6.1.* (semver)
Unaffected: 6.6.55 , ≤ 6.6.* (semver)
Unaffected: 6.10.14 , ≤ 6.10.* (semver)
Unaffected: 6.11.3 , ≤ 6.11.* (semver)
Unaffected: 6.12 , ≤ * (original_commit_for_fix)
Create a notification for this product.
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\"unaffected\", \"version\": \"5.4.285\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.4.*\"}, {\"status\": \"unaffected\", \"version\": \"5.10.227\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.15.168\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.15.*\"}, {\"status\": \"unaffected\", \"version\": \"6.1.113\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.1.*\"}, {\"status\": \"unaffected\", \"version\": \"6.6.55\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.6.*\"}, {\"status\": \"unaffected\", \"version\": \"6.10.14\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.10.*\"}, {\"status\": \"unaffected\", \"version\": \"6.11.3\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"6.11.*\"}, {\"status\": \"unaffected\", \"version\": \"6.12\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"fs/btrfs/relocation.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/1282f001cbf56e5dd6e90a18e205a566793f4be0\"}, {\"url\": \"https://git.kernel.org/stable/c/d73d48acf36f57362df7e4f9d76568168bf5e944\"}, {\"url\": \"https://git.kernel.org/stable/c/37fee9c220b92c3b7bf22b51c51dde5364e7590b\"}, {\"url\": \"https://git.kernel.org/stable/c/d13249c0df7aab885acb149695f82c54c0822a70\"}, {\"url\": \"https://git.kernel.org/stable/c/7ad0c5868f2f0418619089513d95230c66cb7eb4\"}, {\"url\": \"https://git.kernel.org/stable/c/dc02c1440705e3451abd1c2c8114a5c1bb188e9f\"}, {\"url\": \"https://git.kernel.org/stable/c/39356ec0e319ed07627b3a0f402d0608546509e6\"}, {\"url\": \"https://git.kernel.org/stable/c/c3b47f49e83197e8dffd023ec568403bcdbb774b\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nbtrfs: fix a NULL pointer dereference when failed to start a new trasacntion\\n\\n[BUG]\\nSyzbot reported a NULL pointer dereference with the following crash:\\n\\n  FAULT_INJECTION: forcing a failure.\\n   start_transaction+0x830/0x1670 fs/btrfs/transaction.c:676\\n   prepare_to_relocate+0x31f/0x4c0 fs/btrfs/relocation.c:3642\\n   relocate_block_group+0x169/0xd20 fs/btrfs/relocation.c:3678\\n  ...\\n  BTRFS info (device loop0): balance: ended with status: -12\\n  Oops: general protection fault, probably for non-canonical address 0xdffffc00000000cc: 0000 [#1] PREEMPT SMP KASAN NOPTI\\n  KASAN: null-ptr-deref in range [0x0000000000000660-0x0000000000000667]\\n  RIP: 0010:btrfs_update_reloc_root+0x362/0xa80 fs/btrfs/relocation.c:926\\n  Call Trace:\\n   \u003cTASK\u003e\\n   commit_fs_roots+0x2ee/0x720 fs/btrfs/transaction.c:1496\\n   btrfs_commit_transaction+0xfaf/0x3740 fs/btrfs/transaction.c:2430\\n   del_balance_item fs/btrfs/volumes.c:3678 [inline]\\n   reset_balance_state+0x25e/0x3c0 fs/btrfs/volumes.c:3742\\n   btrfs_balance+0xead/0x10c0 fs/btrfs/volumes.c:4574\\n   btrfs_ioctl_balance+0x493/0x7c0 fs/btrfs/ioctl.c:3673\\n   vfs_ioctl fs/ioctl.c:51 [inline]\\n   __do_sys_ioctl fs/ioctl.c:907 [inline]\\n   __se_sys_ioctl+0xf9/0x170 fs/ioctl.c:893\\n   do_syscall_x64 arch/x86/entry/common.c:52 [inline]\\n   do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83\\n   entry_SYSCALL_64_after_hwframe+0x77/0x7f\\n\\n[CAUSE]\\nThe allocation failure happens at the start_transaction() inside\\nprepare_to_relocate(), and during the error handling we call\\nunset_reloc_control(), which makes fs_info-\u003ebalance_ctl to be NULL.\\n\\nThen we continue the error path cleanup in btrfs_balance() by calling\\nreset_balance_state() which will call del_balance_item() to fully delete\\nthe balance item in the root tree.\\n\\nHowever during the small window between set_reloc_contrl() and\\nunset_reloc_control(), we can have a subvolume tree update and created a\\nreloc_root for that subvolume.\\n\\nThen we go into the final btrfs_commit_transaction() of\\ndel_balance_item(), and into btrfs_update_reloc_root() inside\\ncommit_fs_roots().\\n\\nThat function checks if fs_info-\u003ereloc_ctl is in the merge_reloc_tree\\nstage, but since fs_info-\u003ereloc_ctl is NULL, it results a NULL pointer\\ndereference.\\n\\n[FIX]\\nJust add extra check on fs_info-\u003ereloc_ctl inside\\nbtrfs_update_reloc_root(), before checking\\nfs_info-\u003ereloc_ctl-\u003emerge_reloc_tree.\\n\\nThat DEAD_RELOC_TREE handling is to prevent further modification to the\\nreloc tree during merge stage, but since there is no reloc_ctl at all,\\nwe do not need to bother that.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.4.285\", \"versionStartIncluding\": \"2.6.35\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.227\", \"versionStartIncluding\": \"2.6.35\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.168\", \"versionStartIncluding\": \"2.6.35\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.1.113\", \"versionStartIncluding\": \"2.6.35\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.6.55\", \"versionStartIncluding\": \"2.6.35\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.10.14\", \"versionStartIncluding\": \"2.6.35\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.11.3\", \"versionStartIncluding\": \"2.6.35\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"6.12\", \"versionStartIncluding\": \"2.6.35\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-01-05T10:54:10.554Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2024-49868\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-01-05T10:54:10.554Z\", \"dateReserved\": \"2024-10-21T12:17:06.019Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-10-21T18:01:10.722Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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Sightings

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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.