GHSA-G466-9RMR-2M23
Vulnerability from github – Published: 2026-02-04 18:30 – Updated: 2026-02-06 18:30In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix deadlock in wait_current_trans() due to ignored transaction type
When wait_current_trans() is called during start_transaction(), it currently waits for a blocked transaction without considering whether the given transaction type actually needs to wait for that particular transaction state. The btrfs_blocked_trans_types[] array already defines which transaction types should wait for which transaction states, but this check was missing in wait_current_trans().
This can lead to a deadlock scenario involving two transactions and pending ordered extents:
-
Transaction A is in TRANS_STATE_COMMIT_DOING state
-
A worker processing an ordered extent calls start_transaction() with TRANS_JOIN
-
join_transaction() returns -EBUSY because Transaction A is in TRANS_STATE_COMMIT_DOING
-
Transaction A moves to TRANS_STATE_UNBLOCKED and completes
-
A new Transaction B is created (TRANS_STATE_RUNNING)
-
The ordered extent from step 2 is added to Transaction B's pending ordered extents
-
Transaction B immediately starts commit by another task and enters TRANS_STATE_COMMIT_START
-
The worker finally reaches wait_current_trans(), sees Transaction B in TRANS_STATE_COMMIT_START (a blocked state), and waits unconditionally
-
However, TRANS_JOIN should NOT wait for TRANS_STATE_COMMIT_START according to btrfs_blocked_trans_types[]
-
Transaction B is waiting for pending ordered extents to complete
-
Deadlock: Transaction B waits for ordered extent, ordered extent waits for Transaction B
This can be illustrated by the following call stacks: CPU0 CPU1 btrfs_finish_ordered_io() start_transaction(TRANS_JOIN) join_transaction() # -EBUSY (Transaction A is # TRANS_STATE_COMMIT_DOING) # Transaction A completes # Transaction B created # ordered extent added to # Transaction B's pending list btrfs_commit_transaction() # Transaction B enters # TRANS_STATE_COMMIT_START # waiting for pending ordered # extents wait_current_trans() # waits for Transaction B # (should not wait!)
Task bstore_kv_sync in btrfs_commit_transaction waiting for ordered extents:
__schedule+0x2e7/0x8a0 schedule+0x64/0xe0 btrfs_commit_transaction+0xbf7/0xda0 [btrfs] btrfs_sync_file+0x342/0x4d0 [btrfs] __x64_sys_fdatasync+0x4b/0x80 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9
Task kworker in wait_current_trans waiting for transaction commit:
Workqueue: btrfs-syno_nocow btrfs_work_helper [btrfs] __schedule+0x2e7/0x8a0 schedule+0x64/0xe0 wait_current_trans+0xb0/0x110 [btrfs] start_transaction+0x346/0x5b0 [btrfs] btrfs_finish_ordered_io.isra.0+0x49b/0x9c0 [btrfs] btrfs_work_helper+0xe8/0x350 [btrfs] process_one_work+0x1d3/0x3c0 worker_thread+0x4d/0x3e0 kthread+0x12d/0x150 ret_from_fork+0x1f/0x30
Fix this by passing the transaction type to wait_current_trans() and checking btrfs_blocked_trans_types[cur_trans->state] against the given type before deciding to wait. This ensures that transaction types which are allowed to join during certain blocked states will not unnecessarily wait and cause deadlocks.
{
"affected": [],
"aliases": [
"CVE-2025-71194"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-02-04T17:16:11Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix deadlock in wait_current_trans() due to ignored transaction type\n\nWhen wait_current_trans() is called during start_transaction(), it\ncurrently waits for a blocked transaction without considering whether\nthe given transaction type actually needs to wait for that particular\ntransaction state. The btrfs_blocked_trans_types[] array already defines\nwhich transaction types should wait for which transaction states, but\nthis check was missing in wait_current_trans().\n\nThis can lead to a deadlock scenario involving two transactions and\npending ordered extents:\n\n 1. Transaction A is in TRANS_STATE_COMMIT_DOING state\n\n 2. A worker processing an ordered extent calls start_transaction()\n with TRANS_JOIN\n\n 3. join_transaction() returns -EBUSY because Transaction A is in\n TRANS_STATE_COMMIT_DOING\n\n 4. Transaction A moves to TRANS_STATE_UNBLOCKED and completes\n\n 5. A new Transaction B is created (TRANS_STATE_RUNNING)\n\n 6. The ordered extent from step 2 is added to Transaction B\u0027s\n pending ordered extents\n\n 7. Transaction B immediately starts commit by another task and\n enters TRANS_STATE_COMMIT_START\n\n 8. The worker finally reaches wait_current_trans(), sees Transaction B\n in TRANS_STATE_COMMIT_START (a blocked state), and waits\n unconditionally\n\n 9. However, TRANS_JOIN should NOT wait for TRANS_STATE_COMMIT_START\n according to btrfs_blocked_trans_types[]\n\n 10. Transaction B is waiting for pending ordered extents to complete\n\n 11. Deadlock: Transaction B waits for ordered extent, ordered extent\n waits for Transaction B\n\nThis can be illustrated by the following call stacks:\n CPU0 CPU1\n btrfs_finish_ordered_io()\n start_transaction(TRANS_JOIN)\n join_transaction()\n # -EBUSY (Transaction A is\n # TRANS_STATE_COMMIT_DOING)\n # Transaction A completes\n # Transaction B created\n # ordered extent added to\n # Transaction B\u0027s pending list\n btrfs_commit_transaction()\n # Transaction B enters\n # TRANS_STATE_COMMIT_START\n # waiting for pending ordered\n # extents\n wait_current_trans()\n # waits for Transaction B\n # (should not wait!)\n\nTask bstore_kv_sync in btrfs_commit_transaction waiting for ordered\nextents:\n\n __schedule+0x2e7/0x8a0\n schedule+0x64/0xe0\n btrfs_commit_transaction+0xbf7/0xda0 [btrfs]\n btrfs_sync_file+0x342/0x4d0 [btrfs]\n __x64_sys_fdatasync+0x4b/0x80\n do_syscall_64+0x33/0x40\n entry_SYSCALL_64_after_hwframe+0x44/0xa9\n\nTask kworker in wait_current_trans waiting for transaction commit:\n\n Workqueue: btrfs-syno_nocow btrfs_work_helper [btrfs]\n __schedule+0x2e7/0x8a0\n schedule+0x64/0xe0\n wait_current_trans+0xb0/0x110 [btrfs]\n start_transaction+0x346/0x5b0 [btrfs]\n btrfs_finish_ordered_io.isra.0+0x49b/0x9c0 [btrfs]\n btrfs_work_helper+0xe8/0x350 [btrfs]\n process_one_work+0x1d3/0x3c0\n worker_thread+0x4d/0x3e0\n kthread+0x12d/0x150\n ret_from_fork+0x1f/0x30\n\nFix this by passing the transaction type to wait_current_trans() and\nchecking btrfs_blocked_trans_types[cur_trans-\u003estate] against the given\ntype before deciding to wait. This ensures that transaction types which\nare allowed to join during certain blocked states will not unnecessarily\nwait and cause deadlocks.",
"id": "GHSA-g466-9rmr-2m23",
"modified": "2026-02-06T18:30:29Z",
"published": "2026-02-04T18:30:42Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-71194"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5037b342825df7094a4906d1e2a9674baab50cb2"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8b0bb145d3bc264360f525c9717653be3522e528"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/99da896614d17e8a84aeb2b2d464ac046cc8633d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9ac63333d600732a56b35ee1fa46836da671eb50"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d7b04b40ac8e6d814e35202a0e1568809b818295"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/dc84036c173cff6a432d9ab926298850b1d2a659"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/e563f59395981fcd69d130761290929806e728d6"
}
],
"schema_version": "1.4.0",
"severity": []
}
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