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CVE-2021-46958 (GCVE-0-2021-46958)

Vulnerability from cvelistv5 – Published: 2024-02-27 18:46 – Updated: 2026-08-05 08:45
VLAI
Title
btrfs: fix race between transaction aborts and fsyncs leading to use-after-free
Summary
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix race between transaction aborts and fsyncs leading to use-after-free There is a race between a task aborting a transaction during a commit, a task doing an fsync and the transaction kthread, which leads to an use-after-free of the log root tree. When this happens, it results in a stack trace like the following: BTRFS info (device dm-0): forced readonly BTRFS warning (device dm-0): Skipping commit of aborted transaction. BTRFS: error (device dm-0) in cleanup_transaction:1958: errno=-5 IO failure BTRFS warning (device dm-0): lost page write due to IO error on /dev/mapper/error-test (-5) BTRFS warning (device dm-0): Skipping commit of aborted transaction. BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0xa4e8 len 4096 err no 10 BTRFS error (device dm-0): error writing primary super block to device 1 BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e000 len 4096 err no 10 BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e008 len 4096 err no 10 BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e010 len 4096 err no 10 BTRFS: error (device dm-0) in write_all_supers:4110: errno=-5 IO failure (1 errors while writing supers) BTRFS: error (device dm-0) in btrfs_sync_log:3308: errno=-5 IO failure general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b68: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI CPU: 2 PID: 2458471 Comm: fsstress Not tainted 5.12.0-rc5-btrfs-next-84 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014 RIP: 0010:__mutex_lock+0x139/0xa40 Code: c0 74 19 (...) RSP: 0018:ffff9f18830d7b00 EFLAGS: 00010202 RAX: 6b6b6b6b6b6b6b68 RBX: 0000000000000001 RCX: 0000000000000002 RDX: ffffffffb9c54d13 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffff9f18830d7bc0 R08: 0000000000000000 R09: 0000000000000000 R10: ffff9f18830d7be0 R11: 0000000000000001 R12: ffff8c6cd199c040 R13: ffff8c6c95821358 R14: 00000000fffffffb R15: ffff8c6cbcf01358 FS: 00007fa9140c2b80(0000) GS:ffff8c6fac600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fa913d52000 CR3: 000000013d2b4003 CR4: 0000000000370ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: ? __btrfs_handle_fs_error+0xde/0x146 [btrfs] ? btrfs_sync_log+0x7c1/0xf20 [btrfs] ? btrfs_sync_log+0x7c1/0xf20 [btrfs] btrfs_sync_log+0x7c1/0xf20 [btrfs] btrfs_sync_file+0x40c/0x580 [btrfs] do_fsync+0x38/0x70 __x64_sys_fsync+0x10/0x20 do_syscall_64+0x33/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7fa9142a55c3 Code: 8b 15 09 (...) RSP: 002b:00007fff26278d48 EFLAGS: 00000246 ORIG_RAX: 000000000000004a RAX: ffffffffffffffda RBX: 0000563c83cb4560 RCX: 00007fa9142a55c3 RDX: 00007fff26278cb0 RSI: 00007fff26278cb0 RDI: 0000000000000005 RBP: 0000000000000005 R08: 0000000000000001 R09: 00007fff26278d5c R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000340 R13: 00007fff26278de0 R14: 00007fff26278d96 R15: 0000563c83ca57c0 Modules linked in: btrfs dm_zero dm_snapshot dm_thin_pool (...) ---[ end trace ee2f1b19327d791d ]--- The steps that lead to this crash are the following: 1) We are at transaction N; 2) We have two tasks with a transaction handle attached to transaction N. Task A and Task B. Task B is doing an fsync; 3) Task B is at btrfs_sync_log(), and has saved fs_info->log_root_tree into a local variable named 'log_root_tree' at the top of btrfs_sync_log(). Task B is about to call write_all_supers(), but before that... 4) Task A calls btrfs_commit_transaction(), and after it sets the transaction state to TRANS_STATE_COMMIT_START, an error happens before it w ---truncated---
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-08-15 19:27 UTC
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: ef67963dac255b293e19815ea3d440567be4626f , < a4794be7b00b7eda4b45fffd283ab7d76df7e5d6 (git)
Affected: ef67963dac255b293e19815ea3d440567be4626f , < 633f7f216663587f17601eaa1cf2ac3d5654874c (git)
Affected: ef67963dac255b293e19815ea3d440567be4626f , < e2da98788369bfba1138bada72765c47989a4338 (git)
Affected: ef67963dac255b293e19815ea3d440567be4626f , < 061dde8245356d8864d29e25207aa4daa0be4d3c (git)
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Linux Linux Affected: 5.7
Unaffected: 0 , < 5.7 (semver)
Unaffected: 5.10.36 , ≤ 5.10.* (semver)
Unaffected: 5.11.20 , ≤ 5.11.* (semver)
Unaffected: 5.12.3 , ≤ 5.12.* (semver)
Unaffected: 5.13 , ≤ * (original_commit_for_fix)
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix race between transaction aborts and fsyncs leading to use-after-free\n\nThere is a race between a task aborting a transaction during a commit,\na task doing an fsync and the transaction kthread, which leads to an\nuse-after-free of the log root tree. When this happens, it results in a\nstack trace like the following:\n\n  BTRFS info (device dm-0): forced readonly\n  BTRFS warning (device dm-0): Skipping commit of aborted transaction.\n  BTRFS: error (device dm-0) in cleanup_transaction:1958: errno=-5 IO failure\n  BTRFS warning (device dm-0): lost page write due to IO error on /dev/mapper/error-test (-5)\n  BTRFS warning (device dm-0): Skipping commit of aborted transaction.\n  BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0xa4e8 len 4096 err no 10\n  BTRFS error (device dm-0): error writing primary super block to device 1\n  BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e000 len 4096 err no 10\n  BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e008 len 4096 err no 10\n  BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e010 len 4096 err no 10\n  BTRFS: error (device dm-0) in write_all_supers:4110: errno=-5 IO failure (1 errors while writing supers)\n  BTRFS: error (device dm-0) in btrfs_sync_log:3308: errno=-5 IO failure\n  general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b68: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI\n  CPU: 2 PID: 2458471 Comm: fsstress Not tainted 5.12.0-rc5-btrfs-next-84 #1\n  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014\n  RIP: 0010:__mutex_lock+0x139/0xa40\n  Code: c0 74 19 (...)\n  RSP: 0018:ffff9f18830d7b00 EFLAGS: 00010202\n  RAX: 6b6b6b6b6b6b6b68 RBX: 0000000000000001 RCX: 0000000000000002\n  RDX: ffffffffb9c54d13 RSI: 0000000000000000 RDI: 0000000000000000\n  RBP: ffff9f18830d7bc0 R08: 0000000000000000 R09: 0000000000000000\n  R10: ffff9f18830d7be0 R11: 0000000000000001 R12: ffff8c6cd199c040\n  R13: ffff8c6c95821358 R14: 00000000fffffffb R15: ffff8c6cbcf01358\n  FS:  00007fa9140c2b80(0000) GS:ffff8c6fac600000(0000) knlGS:0000000000000000\n  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\n  CR2: 00007fa913d52000 CR3: 000000013d2b4003 CR4: 0000000000370ee0\n  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\n  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\n  Call Trace:\n   ? __btrfs_handle_fs_error+0xde/0x146 [btrfs]\n   ? btrfs_sync_log+0x7c1/0xf20 [btrfs]\n   ? btrfs_sync_log+0x7c1/0xf20 [btrfs]\n   btrfs_sync_log+0x7c1/0xf20 [btrfs]\n   btrfs_sync_file+0x40c/0x580 [btrfs]\n   do_fsync+0x38/0x70\n   __x64_sys_fsync+0x10/0x20\n   do_syscall_64+0x33/0x80\n   entry_SYSCALL_64_after_hwframe+0x44/0xae\n  RIP: 0033:0x7fa9142a55c3\n  Code: 8b 15 09 (...)\n  RSP: 002b:00007fff26278d48 EFLAGS: 00000246 ORIG_RAX: 000000000000004a\n  RAX: ffffffffffffffda RBX: 0000563c83cb4560 RCX: 00007fa9142a55c3\n  RDX: 00007fff26278cb0 RSI: 00007fff26278cb0 RDI: 0000000000000005\n  RBP: 0000000000000005 R08: 0000000000000001 R09: 00007fff26278d5c\n  R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000340\n  R13: 00007fff26278de0 R14: 00007fff26278d96 R15: 0000563c83ca57c0\n  Modules linked in: btrfs dm_zero dm_snapshot dm_thin_pool (...)\n  ---[ end trace ee2f1b19327d791d ]---\n\nThe steps that lead to this crash are the following:\n\n1) We are at transaction N;\n\n2) We have two tasks with a transaction handle attached to transaction N.\n   Task A and Task B. Task B is doing an fsync;\n\n3) Task B is at btrfs_sync_log(), and has saved fs_info-\u003elog_root_tree\n   into a local variable named \u0027log_root_tree\u0027 at the top of\n   btrfs_sync_log(). Task B is about to call write_all_supers(), but\n   before that...\n\n4) Task A calls btrfs_commit_transaction(), and after it sets the\n   transaction state to TRANS_STATE_COMMIT_START, an error happens before\n   it w\n---truncated---"
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    "nvd": "{\"cve\":{\"id\":\"CVE-2021-46958\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2024-02-27T19:04:06.813\",\"lastModified\":\"2026-08-04T10:16:38.230\",\"vulnStatus\":\"Modified\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nbtrfs: fix race between transaction aborts and fsyncs leading to use-after-free\\n\\nThere is a race between a task aborting a transaction during a commit,\\na task doing an fsync and the transaction kthread, which leads to an\\nuse-after-free of the log root tree. When this happens, it results in a\\nstack trace like the following:\\n\\n  BTRFS info (device dm-0): forced readonly\\n  BTRFS warning (device dm-0): Skipping commit of aborted transaction.\\n  BTRFS: error (device dm-0) in cleanup_transaction:1958: errno=-5 IO failure\\n  BTRFS warning (device dm-0): lost page write due to IO error on /dev/mapper/error-test (-5)\\n  BTRFS warning (device dm-0): Skipping commit of aborted transaction.\\n  BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0xa4e8 len 4096 err no 10\\n  BTRFS error (device dm-0): error writing primary super block to device 1\\n  BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e000 len 4096 err no 10\\n  BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e008 len 4096 err no 10\\n  BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e010 len 4096 err no 10\\n  BTRFS: error (device dm-0) in write_all_supers:4110: errno=-5 IO failure (1 errors while writing supers)\\n  BTRFS: error (device dm-0) in btrfs_sync_log:3308: errno=-5 IO failure\\n  general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b68: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI\\n  CPU: 2 PID: 2458471 Comm: fsstress Not tainted 5.12.0-rc5-btrfs-next-84 #1\\n  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014\\n  RIP: 0010:__mutex_lock+0x139/0xa40\\n  Code: c0 74 19 (...)\\n  RSP: 0018:ffff9f18830d7b00 EFLAGS: 00010202\\n  RAX: 6b6b6b6b6b6b6b68 RBX: 0000000000000001 RCX: 0000000000000002\\n  RDX: ffffffffb9c54d13 RSI: 0000000000000000 RDI: 0000000000000000\\n  RBP: ffff9f18830d7bc0 R08: 0000000000000000 R09: 0000000000000000\\n  R10: ffff9f18830d7be0 R11: 0000000000000001 R12: ffff8c6cd199c040\\n  R13: ffff8c6c95821358 R14: 00000000fffffffb R15: ffff8c6cbcf01358\\n  FS:  00007fa9140c2b80(0000) GS:ffff8c6fac600000(0000) knlGS:0000000000000000\\n  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\\n  CR2: 00007fa913d52000 CR3: 000000013d2b4003 CR4: 0000000000370ee0\\n  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\\n  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\\n  Call Trace:\\n   ? __btrfs_handle_fs_error+0xde/0x146 [btrfs]\\n   ? btrfs_sync_log+0x7c1/0xf20 [btrfs]\\n   ? btrfs_sync_log+0x7c1/0xf20 [btrfs]\\n   btrfs_sync_log+0x7c1/0xf20 [btrfs]\\n   btrfs_sync_file+0x40c/0x580 [btrfs]\\n   do_fsync+0x38/0x70\\n   __x64_sys_fsync+0x10/0x20\\n   do_syscall_64+0x33/0x80\\n   entry_SYSCALL_64_after_hwframe+0x44/0xae\\n  RIP: 0033:0x7fa9142a55c3\\n  Code: 8b 15 09 (...)\\n  RSP: 002b:00007fff26278d48 EFLAGS: 00000246 ORIG_RAX: 000000000000004a\\n  RAX: ffffffffffffffda RBX: 0000563c83cb4560 RCX: 00007fa9142a55c3\\n  RDX: 00007fff26278cb0 RSI: 00007fff26278cb0 RDI: 0000000000000005\\n  RBP: 0000000000000005 R08: 0000000000000001 R09: 00007fff26278d5c\\n  R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000340\\n  R13: 00007fff26278de0 R14: 00007fff26278d96 R15: 0000563c83ca57c0\\n  Modules linked in: btrfs dm_zero dm_snapshot dm_thin_pool (...)\\n  ---[ end trace ee2f1b19327d791d ]---\\n\\nThe steps that lead to this crash are the following:\\n\\n1) We are at transaction N;\\n\\n2) We have two tasks with a transaction handle attached to transaction N.\\n   Task A and Task B. Task B is doing an fsync;\\n\\n3) Task B is at btrfs_sync_log(), and has saved fs_info-\u003elog_root_tree\\n   into a local variable named \u0027log_root_tree\u0027 at the top of\\n   btrfs_sync_log(). Task B is about to call write_all_supers(), but\\n   before that...\\n\\n4) Task A calls btrfs_commit_transaction(), and after it sets the\\n   transaction state to TRANS_STATE_COMMIT_START, an error happens before\\n   it w\\n---truncated---\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: btrfs: corrige la ejecuci\u00f3n entre transacciones abortadas y fsyncs que conducen a use-after-free. Hay una carrera entre una tarea que aborta una transacci\u00f3n durante un commit, una tarea que realiza una fsync y la transacci\u00f3n. kthread, lo que conduce a un use-after-free del \u00e1rbol ra\u00edz del registro. Cuando esto sucede, se genera un seguimiento de pila como el siguiente: Informaci\u00f3n BTRFS (dispositivo dm-0): solo lectura forzada Advertencia BTRFS (dispositivo dm-0): omitir confirmaci\u00f3n de transacci\u00f3n abortada. BTRFS: error (dispositivo dm-0) en cleanup_transaction:1958: errno=-5 falla de IO Advertencia de BTRFS (dispositivo dm-0): escritura de p\u00e1gina perdida debido a un error de IO en /dev/mapper/error-test (-5) BTRFS Advertencia (dispositivo dm-0): omitir confirmaci\u00f3n de transacci\u00f3n abortada. Advertencia BTRFS (dispositivo dm-0): IO directa fall\u00f3 en 261 rw 0,0 sector 0xa4e8 len 4096 err no 10 Error BTRFS (dispositivo dm-0): error al escribir el superbloque primario en el dispositivo 1 Advertencia BTRFS (dispositivo dm-0) : error de IO directo ino 261 rw 0,0 sector 0x12e000 len 4096 err no 10 advertencia BTRFS (dispositivo dm-0): error de IO directo ino 261 rw 0,0 sector 0x12e008 len 4096 error no 10 advertencia BTRFS (dispositivo dm-0) : error de IO directo ino 261 rw 0,0 sector 0x12e010 len 4096 error no 10 BTRFS: error (dispositivo dm-0) en write_all_supers:4110: errno=-5 error de IO (1 error al escribir supers) BTRFS: error (dispositivo dm -0) en btrfs_sync_log:3308: errno=-5 Fallo de E/S Fallo de protecci\u00f3n general, probablemente para la direcci\u00f3n no can\u00f3nica 0x6b6b6b6b6b6b6b68: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI CPU: 2 PID: 2458471 Comm: fsstress Not tainted 5.12.0- rc5-btrfs-next-84 #1 Nombre del hardware: PC est\u00e1ndar QEMU (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 01/04/2014 RIP: 0010:__mutex_lock+ 0x139/0xa40 C\u00f3digo: c0 74 19 (...) RSP: 0018:ffff9f18830d7b00 EFLAGS: 00010202 RAX: 6b6b6b6b6b6b6b68 RBX: 0000000000000001 RCX: 00000000000000002 RD X: ffffffffb9c54d13 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffff9f18830d7bc0 R08: 00000000000000000 R09: 0000000000000000 R10: ffff9f18830d7be0 R11: 0000000000000001 R12: ffff8c6cd199c040 R13: ffff8c6c95821358 R14: 00000000fffffffb R15: ffff8c6cbcf01358 FS: 00007fa9140c2b 80(0000) GS:ffff8c6fac600000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fa913d52000 CR3: 000000013d2 b4003 CR4 : 0000000000370ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 00000000000000000 DR6: 00000000fffe0ff0 DR7: 000000 0000000400 Rastreo de llamadas: ? __btrfs_handle_fs_error+0xde/0x146 [btrfs] ? btrfs_sync_log+0x7c1/0xf20 [btrfs]? btrfs_sync_log+0x7c1/0xf20 [btrfs] btrfs_sync_log+0x7c1/0xf20 [btrfs] btrfs_sync_file+0x40c/0x580 [btrfs] do_fsync+0x38/0x70 __x64_sys_fsync+0x10/0x20 do_syscall_64+ 0x33/0x80 Entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7fa9142a55c3 C\u00f3digo : 8b 15 09 (...) RSP: 002b:00007fff26278d48 EFLAGS: 00000246 ORIG_RAX: 000000000000004a RAX: ffffffffffffffda RBX: 0000563c83cb4560 RCX: 00007fa9142a55c 3 RDX: 00007fff26278cb0 RSI: 00007fff26278cb0 RDI: 0000000000000005 RBP: 0000000000000005 R08: 000000000000000001 R09: 00007fff26278d5c R10: 0 000000000000000 R11: 0000000000000246 R12: 0000000000000340 R13: 00007fff26278de0 R14: 00007fff26278d96 R15: 0000563c83ca57c0 M\u00f3dulos vinculados en: btrfs dm_zero dm_snapshot dm _thin_pool (...) ---[ end trace ee2f1b19327d791d ]--- Los pasos que conducen a este bloqueo son los siguientes: 1) Estamos en la transacci\u00f3n N; 2) Tenemos dos tareas con un identificador de transacci\u00f3n adjunto a la transacci\u00f3n N. Tarea A y Tarea B. La tarea B est\u00e1 realizando una sincronizaci\u00f3n f; 3) La tarea B est\u00e1 en btrfs_sync_log() y ha guardado fs_info-\u0026gt;log_root_tree en una variable local llamada \u0027log_root_tree\u0027 en la parte superior de btrfs_sync_log().---truncado---\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"fs/btrfs/transaction.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"ef67963dac255b293e19815ea3d440567be4626f\",\"lessThan\":\"a4794be7b00b7eda4b45fffd283ab7d76df7e5d6\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"ef67963dac255b293e19815ea3d440567be4626f\",\"lessThan\":\"633f7f216663587f17601eaa1cf2ac3d5654874c\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"ef67963dac255b293e19815ea3d440567be4626f\",\"lessThan\":\"e2da98788369bfba1138bada72765c47989a4338\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"ef67963dac255b293e19815ea3d440567be4626f\",\"lessThan\":\"061dde8245356d8864d29e25207aa4daa0be4d3c\",\"versionType\":\"git\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"fs/btrfs/transaction.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.7\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.7\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.10.36\",\"lessThanOrEqual\":\"5.10.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.11.20\",\"lessThanOrEqual\":\"5.11.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.12.3\",\"lessThanOrEqual\":\"5.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.13\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.8,\"impactScore\":5.9},{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H\",\"baseScore\":4.7,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.0,\"impactScore\":3.6}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2024-08-15T19:27:46.078537Z\",\"id\":\"CVE-2021-46958\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"partial\"}],\"role\":\"CISA 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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-04T21:37:50+00:00",
      "cve": "CVE-2021-46958",
      "id": "CVE-2021-46958",
      "initial_release_date": "2021-01-01T00:00:00+00:00",
      "product_status:known_not_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: btrfs: fix race between transaction aborts and fsyncs leading to use-after-free",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-46958.json",
      "version": "3"
    },
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      "containers": "{\"adp\": [{\"title\": \"CVE Program Container\", \"references\": [{\"url\": \"https://git.kernel.org/stable/c/a4794be7b00b7eda4b45fffd283ab7d76df7e5d6\", \"tags\": [\"x_transferred\"]}, {\"url\": \"https://git.kernel.org/stable/c/633f7f216663587f17601eaa1cf2ac3d5654874c\", \"tags\": [\"x_transferred\"]}, {\"url\": \"https://git.kernel.org/stable/c/e2da98788369bfba1138bada72765c47989a4338\", \"tags\": [\"x_transferred\"]}, {\"url\": \"https://git.kernel.org/stable/c/061dde8245356d8864d29e25207aa4daa0be4d3c\", \"tags\": [\"x_transferred\"]}], \"providerMetadata\": {\"orgId\": \"af854a3a-2127-422b-91ae-364da2661108\", \"shortName\": \"CVE\", \"dateUpdated\": \"2024-08-04T05:17:42.988Z\"}}, {\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2021-46958\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2024-08-15T19:27:46.078537Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2024-08-15T19:28:02.844Z\"}}], \"cna\": {\"title\": \"btrfs: fix race between transaction aborts and fsyncs leading to use-after-free\", \"metrics\": [{\"cvssV3_1\": {\"version\": \"3.1\", \"baseScore\": 7.8, \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"AV:L - The vulnerable path is reached through local fsync/fdatasync on a mounted btrfs filesystem (fsync \\u2192 btrfs_sync_file \\u2192 btrfs_sync_log), not via network packet processing or physical device attachment.\\nAC:L - An attacker controls both sides of the race by running concurrent threads that induce a transaction abort (many unprivileged write/create/unlink/ENOSPC abort sites) while another thread calls fsync, and can retry indefinitely until the kthread frees log_root_tree under the racing fsync.\\nPR:L - Any unprivileged local user with access to a file on a mounted btrfs volume can call fsync and perform ordinary file operations that abort transactions; no capabilities or init-namespace root are required.\\nUI:N - btrfs is commonly already mounted (desktops, NAS, Android, containers); the attacker drives writes and fsync from their own processes with no victim mount or open required.\\nS:U - The use-after-free corrupts kernel heap state within the same OS/kernel security authority; there is no VM escape, IOMMU bypass, or sandbox boundary crossing.\\nC:H - The race frees the log_root_tree (struct btrfs_root) while btrfs_sync_log still holds and later dereferences that pointer (mutex_lock on log_mutex), which after slab reclaim/heap spray enables arbitrary kernel memory reads.\\nI:H - Use-after-free of a kernel object with subsequent mutex and list operations on attacker-influenced freed memory yields write and control-flow hijack primitives suitable for privilege escalation.\\nA:H - The demonstrated impact is a general protection fault / kernel oops in __mutex_lock via the freed log_root_tree pointer during fsync, which is a full host availability failure.\"}]}], \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"ef67963dac255b293e19815ea3d440567be4626f\", \"lessThan\": \"a4794be7b00b7eda4b45fffd283ab7d76df7e5d6\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"ef67963dac255b293e19815ea3d440567be4626f\", \"lessThan\": \"633f7f216663587f17601eaa1cf2ac3d5654874c\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"ef67963dac255b293e19815ea3d440567be4626f\", \"lessThan\": \"e2da98788369bfba1138bada72765c47989a4338\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"ef67963dac255b293e19815ea3d440567be4626f\", \"lessThan\": \"061dde8245356d8864d29e25207aa4daa0be4d3c\", \"versionType\": \"git\"}], \"programFiles\": [\"fs/btrfs/transaction.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"5.7\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"5.7\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"5.10.36\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.11.20\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.11.*\"}, {\"status\": \"unaffected\", \"version\": \"5.12.3\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.12.*\"}, {\"status\": \"unaffected\", \"version\": \"5.13\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"fs/btrfs/transaction.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/a4794be7b00b7eda4b45fffd283ab7d76df7e5d6\"}, {\"url\": \"https://git.kernel.org/stable/c/633f7f216663587f17601eaa1cf2ac3d5654874c\"}, {\"url\": \"https://git.kernel.org/stable/c/e2da98788369bfba1138bada72765c47989a4338\"}, {\"url\": \"https://git.kernel.org/stable/c/061dde8245356d8864d29e25207aa4daa0be4d3c\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nbtrfs: fix race between transaction aborts and fsyncs leading to use-after-free\\n\\nThere is a race between a task aborting a transaction during a commit,\\na task doing an fsync and the transaction kthread, which leads to an\\nuse-after-free of the log root tree. When this happens, it results in a\\nstack trace like the following:\\n\\n  BTRFS info (device dm-0): forced readonly\\n  BTRFS warning (device dm-0): Skipping commit of aborted transaction.\\n  BTRFS: error (device dm-0) in cleanup_transaction:1958: errno=-5 IO failure\\n  BTRFS warning (device dm-0): lost page write due to IO error on /dev/mapper/error-test (-5)\\n  BTRFS warning (device dm-0): Skipping commit of aborted transaction.\\n  BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0xa4e8 len 4096 err no 10\\n  BTRFS error (device dm-0): error writing primary super block to device 1\\n  BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e000 len 4096 err no 10\\n  BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e008 len 4096 err no 10\\n  BTRFS warning (device dm-0): direct IO failed ino 261 rw 0,0 sector 0x12e010 len 4096 err no 10\\n  BTRFS: error (device dm-0) in write_all_supers:4110: errno=-5 IO failure (1 errors while writing supers)\\n  BTRFS: error (device dm-0) in btrfs_sync_log:3308: errno=-5 IO failure\\n  general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6b68: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC PTI\\n  CPU: 2 PID: 2458471 Comm: fsstress Not tainted 5.12.0-rc5-btrfs-next-84 #1\\n  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014\\n  RIP: 0010:__mutex_lock+0x139/0xa40\\n  Code: c0 74 19 (...)\\n  RSP: 0018:ffff9f18830d7b00 EFLAGS: 00010202\\n  RAX: 6b6b6b6b6b6b6b68 RBX: 0000000000000001 RCX: 0000000000000002\\n  RDX: ffffffffb9c54d13 RSI: 0000000000000000 RDI: 0000000000000000\\n  RBP: ffff9f18830d7bc0 R08: 0000000000000000 R09: 0000000000000000\\n  R10: ffff9f18830d7be0 R11: 0000000000000001 R12: ffff8c6cd199c040\\n  R13: ffff8c6c95821358 R14: 00000000fffffffb R15: ffff8c6cbcf01358\\n  FS:  00007fa9140c2b80(0000) GS:ffff8c6fac600000(0000) knlGS:0000000000000000\\n  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033\\n  CR2: 00007fa913d52000 CR3: 000000013d2b4003 CR4: 0000000000370ee0\\n  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000\\n  DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400\\n  Call Trace:\\n   ? __btrfs_handle_fs_error+0xde/0x146 [btrfs]\\n   ? btrfs_sync_log+0x7c1/0xf20 [btrfs]\\n   ? btrfs_sync_log+0x7c1/0xf20 [btrfs]\\n   btrfs_sync_log+0x7c1/0xf20 [btrfs]\\n   btrfs_sync_file+0x40c/0x580 [btrfs]\\n   do_fsync+0x38/0x70\\n   __x64_sys_fsync+0x10/0x20\\n   do_syscall_64+0x33/0x80\\n   entry_SYSCALL_64_after_hwframe+0x44/0xae\\n  RIP: 0033:0x7fa9142a55c3\\n  Code: 8b 15 09 (...)\\n  RSP: 002b:00007fff26278d48 EFLAGS: 00000246 ORIG_RAX: 000000000000004a\\n  RAX: ffffffffffffffda RBX: 0000563c83cb4560 RCX: 00007fa9142a55c3\\n  RDX: 00007fff26278cb0 RSI: 00007fff26278cb0 RDI: 0000000000000005\\n  RBP: 0000000000000005 R08: 0000000000000001 R09: 00007fff26278d5c\\n  R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000340\\n  R13: 00007fff26278de0 R14: 00007fff26278d96 R15: 0000563c83ca57c0\\n  Modules linked in: btrfs dm_zero dm_snapshot dm_thin_pool (...)\\n  ---[ end trace ee2f1b19327d791d ]---\\n\\nThe steps that lead to this crash are the following:\\n\\n1) We are at transaction N;\\n\\n2) We have two tasks with a transaction handle attached to transaction N.\\n   Task A and Task B. Task B is doing an fsync;\\n\\n3) Task B is at btrfs_sync_log(), and has saved fs_info-\u003elog_root_tree\\n   into a local variable named \u0027log_root_tree\u0027 at the top of\\n   btrfs_sync_log(). Task B is about to call write_all_supers(), but\\n   before that...\\n\\n4) Task A calls btrfs_commit_transaction(), and after it sets the\\n   transaction state to TRANS_STATE_COMMIT_START, an error happens before\\n   it w\\n---truncated---\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.36\", \"versionStartIncluding\": \"5.7\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.11.20\", \"versionStartIncluding\": \"5.7\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.12.3\", \"versionStartIncluding\": \"5.7\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.13\", \"versionStartIncluding\": \"5.7\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-08-05T08:45:13.853Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-46958\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-05T08:45:13.853Z\", \"dateReserved\": \"2024-02-27T18:42:55.939Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-02-27T18:46:59.315Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • 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.