CVE-2021-46958

btrfs: fix race between transaction aborts and fsyncs leading to use-after-free

Severity Score

"-"

*CVSS v-

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

*Multiple Sources

Exploited in Wild

*KEV

Decision

Track

*SSVC

Descriptions

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---

En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: btrfs: corrige la ejecución entre transacciones abortadas y fsyncs que conducen a use-after-free. Hay una carrera entre una tarea que aborta una transacción durante un commit, una tarea que realiza una fsync y la transacción. kthread, lo que conduce a un use-after-free del árbol raíz del registro. Cuando esto sucede, se genera un seguimiento de pila como el siguiente: Información BTRFS (dispositivo dm-0): solo lectura forzada Advertencia BTRFS (dispositivo dm-0): omitir confirmación de transacción abortada. BTRFS: error (dispositivo dm-0) en cleanup_transaction:1958: errno=-5 falla de IO Advertencia de BTRFS (dispositivo dm-0): escritura de página perdida debido a un error de IO en /dev/mapper/error-test (-5) BTRFS Advertencia (dispositivo dm-0): omitir confirmación de transacción abortada. Advertencia BTRFS (dispositivo dm-0): IO directa falló 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 protección general, probablemente para la dirección no canónica 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 estándar QEMU (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 01/04/2014 RIP: 0010:__mutex_lock+ 0x139/0xa40 Código: 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 Código : 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 Módulos 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 transacción N; 2) Tenemos dos tareas con un identificador de transacción adjunto a la transacción N. Tarea A y Tarea B. La tarea B está realizando una sincronización f; 3) La tarea B está en btrfs_sync_log() y ha guardado fs_info->log_root_tree en una variable local llamada 'log_root_tree' en la parte superior de btrfs_sync_log().---truncado---

*Credits: N/A

CVSS Scores

Attack Vector

Attack Complexity

Privileges Required

User Interaction

Scope

Confidentiality

Integrity

Availability

* Common Vulnerability Scoring System

SSVC

Decision:Track

Exploitation

None

Automatable

Tech. Impact

Partial

* Organization's Worst-case Scenario

Timeline

2024-02-27 CVE Reserved
2024-02-27 CVE Published
2024-02-28 EPSS Updated
2024-08-15 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CAPEC

References (5)

URL	Tag	Source
https://git.kernel.org/stable/c/ef67963dac255b293e19815ea3d440567be4626f	Vuln. Introduced

URL	Date	SRC

URL	Date	SRC
https://git.kernel.org/stable/c/a4794be7b00b7eda4b45fffd283ab7d76df7e5d6	2021-05-11
https://git.kernel.org/stable/c/633f7f216663587f17601eaa1cf2ac3d5654874c	2021-05-12
https://git.kernel.org/stable/c/e2da98788369bfba1138bada72765c47989a4338	2021-05-12
https://git.kernel.org/stable/c/061dde8245356d8864d29e25207aa4daa0be4d3c	2021-04-19

URL	Date	SRC

Affected Vendors, Products, and Versions

Vendor		Product				Version		Other		Status
Vendor	Product	Version	Other	Status	<-- -->	Vendor	Product	Version	Other	Status
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.7 < 5.10.36 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.7 < 5.10.36"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.7 < 5.11.20 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.7 < 5.11.20"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.7 < 5.12.3 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.7 < 5.12.3"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.7 < 5.13 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.7 < 5.13"		en		Affected