CVE-2021-47508

btrfs: free exchange changeset on failures

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: free exchange changeset on failures

Fstests runs on my VMs have show several kmemleak reports like the following.

unreferenced object 0xffff88811ae59080 (size 64):
comm "xfs_io", pid 12124, jiffies 4294987392 (age 6.368s)
hex dump (first 32 bytes):
00 c0 1c 00 00 00 00 00 ff cf 1c 00 00 00 00 00 ................
90 97 e5 1a 81 88 ff ff 90 97 e5 1a 81 88 ff ff ................
backtrace:
[<00000000ac0176d2>] ulist_add_merge+0x60/0x150 [btrfs]
[<0000000076e9f312>] set_state_bits+0x86/0xc0 [btrfs]
[<0000000014fe73d6>] set_extent_bit+0x270/0x690 [btrfs]
[<000000004f675208>] set_record_extent_bits+0x19/0x20 [btrfs]
[<00000000b96137b1>] qgroup_reserve_data+0x274/0x310 [btrfs]
[<0000000057e9dcbb>] btrfs_check_data_free_space+0x5c/0xa0 [btrfs]
[<0000000019c4511d>] btrfs_delalloc_reserve_space+0x1b/0xa0 [btrfs]
[<000000006d37e007>] btrfs_dio_iomap_begin+0x415/0x970 [btrfs]
[<00000000fb8a74b8>] iomap_iter+0x161/0x1e0
[<0000000071dff6ff>] __iomap_dio_rw+0x1df/0x700
[<000000002567ba53>] iomap_dio_rw+0x5/0x20
[<0000000072e555f8>] btrfs_file_write_iter+0x290/0x530 [btrfs]
[<000000005eb3d845>] new_sync_write+0x106/0x180
[<000000003fb505bf>] vfs_write+0x24d/0x2f0
[<000000009bb57d37>] __x64_sys_pwrite64+0x69/0xa0
[<000000003eba3fdf>] do_syscall_64+0x43/0x90

In case brtfs_qgroup_reserve_data() or btrfs_delalloc_reserve_metadata()
fail the allocated extent_changeset will not be freed.

So in btrfs_check_data_free_space() and btrfs_delalloc_reserve_space()
free the allocated extent_changeset to get rid of the allocated memory.

The issue currently only happens in the direct IO write path, but only
after 65b3c08606e5 ("btrfs: fix ENOSPC failure when attempting direct IO
write into NOCOW range"), and also at defrag_one_locked_target(). Every
other place is always calling extent_changeset_free() even if its call
to btrfs_delalloc_reserve_space() or btrfs_check_data_free_space() has
failed.

En el kernel de Linux, se resolvió la siguiente vulnerabilidad: btrfs: conjunto de cambios de intercambio gratuito en caso de fallas. Las ejecuciones de Fstests en mis VM han mostrado varios informes de kmemleak como el siguiente. objeto sin referencia 0xffff88811ae59080 (tamaño 64): comm "xfs_io", pid 12124, jiffies 4294987392 (edad 6,368 s) volcado hexadecimal (primeros 32 bytes): 00 c0 1c 00 00 00 00 00 ff cf 1c 00 00 00 00... ............. 90 97 e5 1a 81 88 ff ff 90 97 e5 1a 81 88 ff ff ................ retroceso: [<00000000ac0176d2 >] ulist_add_merge+0x60/0x150 [btrfs] [<0000000076e9f312>] set_state_bits+0x86/0xc0 [btrfs] [<0000000014fe73d6>] set_extent_bit+0x270/0x690 [btrfs] [<000000004f 675208>] set_record_extent_bits+0x19/0x20 [btrfs] [ <00000000b96137b1>] qgroup_reserve_data+0x274/0x310 [btrfs] [<0000000057e9dcbb>] btrfs_check_data_free_space+0x5c/0xa0 [btrfs] [<0000000019c4511d>] +0x1b/0xa0 [btrfs] [<000000006d37e007>] btrfs_dio_iomap_begin+0x415/0x970 [btrfs ] [<00000000fb8a74b8>] iomap_iter+0x161/0x1e0 [<0000000071dff6ff>] __iomap_dio_rw+0x1df/0x700 [<000000002567ba53>] iomap_dio_rw+0x5/0x20 [<000000 0072e555f8>] btrfs_file_write_iter+0x290/0x530 [btrfs] [<000000005eb3d845>] new_sync_write +0x106/0x180 [<000000003fb505bf>] vfs_write+0x24d/0x2f0 [<000000009bb57d37>] __x64_sys_pwrite64+0x69/0xa0 [<000000003eba3fdf>] 3/0x90 En caso de que brtfs_qgroup_reserve_data() o btrfs_delalloc_reserve_metadata() fallen, el conjunto de cambios asignado no será liberado. Entonces, en btrfs_check_data_free_space() y btrfs_delalloc_reserve_space() libera el extend_changeset asignado para deshacerte de la memoria asignada. Actualmente, el problema solo ocurre en la ruta de escritura de IO directa, pero solo después de 65b3c08606e5 ("btrfs: corrige la falla de ENOSPC al intentar escribir IO directa en el rango NOCOW"), y también en defrag_one_locked_target(). Todos los demás lugares siempre llaman a extend_changeset_free() incluso si su llamada a btrfs_delalloc_reserve_space() o btrfs_check_data_free_space() ha fallado.

*Credits: N/A

CVSS Scores

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Scope

Confidentiality

Integrity

Availability

* Common Vulnerability Scoring System

SSVC

Decision:Track

Exploitation

None

Automatable

Tech. Impact

Partial

* Organization's Worst-case Scenario

Timeline

2024-05-22 CVE Reserved
2024-05-24 CVE Published
2024-05-25 EPSS Updated
2024-09-11 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CAPEC

References (2)

URL	Tag	Source

URL	Date	SRC

URL	Date	SRC
https://git.kernel.org/stable/c/ca06c5cb1b6dbfe67655b33c02fc394d65824519	2021-12-14
https://git.kernel.org/stable/c/da5e817d9d75422eaaa05490d0b9a5e328fc1a51	2021-12-08

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"				< 5.15.8 Search vendor "Linux" for product "Linux Kernel" and version " < 5.15.8"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 5.16 Search vendor "Linux" for product "Linux Kernel" and version " < 5.16"		en		Affected