CVE-2021-47435

dm: fix mempool NULL pointer race when completing IO

Severity Score

5.5

*CVSS v3.1

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:

dm: fix mempool NULL pointer race when completing IO

dm_io_dec_pending() calls end_io_acct() first and will then dec md
in-flight pending count. But if a task is swapping DM table at same
time this can result in a crash due to mempool->elements being NULL:

task1 task2
do_resume
->do_suspend
->dm_wait_for_completion
bio_endio
->clone_endio
->dm_io_dec_pending
->end_io_acct
->wakeup task1
->dm_swap_table
->__bind
->__bind_mempools
->bioset_exit
->mempool_exit
->free_io

[ 67.330330] Unable to handle kernel NULL pointer dereference at
virtual address 0000000000000000
......
[ 67.330494] pstate: 80400085 (Nzcv daIf +PAN -UAO)
[ 67.330510] pc : mempool_free+0x70/0xa0
[ 67.330515] lr : mempool_free+0x4c/0xa0
[ 67.330520] sp : ffffff8008013b20
[ 67.330524] x29: ffffff8008013b20 x28: 0000000000000004
[ 67.330530] x27: ffffffa8c2ff40a0 x26: 00000000ffff1cc8
[ 67.330535] x25: 0000000000000000 x24: ffffffdada34c800
[ 67.330541] x23: 0000000000000000 x22: ffffffdada34c800
[ 67.330547] x21: 00000000ffff1cc8 x20: ffffffd9a1304d80
[ 67.330552] x19: ffffffdada34c970 x18: 000000b312625d9c
[ 67.330558] x17: 00000000002dcfbf x16: 00000000000006dd
[ 67.330563] x15: 000000000093b41e x14: 0000000000000010
[ 67.330569] x13: 0000000000007f7a x12: 0000000034155555
[ 67.330574] x11: 0000000000000001 x10: 0000000000000001
[ 67.330579] x9 : 0000000000000000 x8 : 0000000000000000
[ 67.330585] x7 : 0000000000000000 x6 : ffffff80148b5c1a
[ 67.330590] x5 : ffffff8008013ae0 x4 : 0000000000000001
[ 67.330596] x3 : ffffff80080139c8 x2 : ffffff801083bab8
[ 67.330601] x1 : 0000000000000000 x0 : ffffffdada34c970
[ 67.330609] Call trace:
[ 67.330616] mempool_free+0x70/0xa0
[ 67.330627] bio_put+0xf8/0x110
[ 67.330638] dec_pending+0x13c/0x230
[ 67.330644] clone_endio+0x90/0x180
[ 67.330649] bio_endio+0x198/0x1b8
[ 67.330655] dec_pending+0x190/0x230
[ 67.330660] clone_endio+0x90/0x180
[ 67.330665] bio_endio+0x198/0x1b8
[ 67.330673] blk_update_request+0x214/0x428
[ 67.330683] scsi_end_request+0x2c/0x300
[ 67.330688] scsi_io_completion+0xa0/0x710
[ 67.330695] scsi_finish_command+0xd8/0x110
[ 67.330700] scsi_softirq_done+0x114/0x148
[ 67.330708] blk_done_softirq+0x74/0xd0
[ 67.330716] __do_softirq+0x18c/0x374
[ 67.330724] irq_exit+0xb4/0xb8
[ 67.330732] __handle_domain_irq+0x84/0xc0
[ 67.330737] gic_handle_irq+0x148/0x1b0
[ 67.330744] el1_irq+0xe8/0x190
[ 67.330753] lpm_cpuidle_enter+0x4f8/0x538
[ 67.330759] cpuidle_enter_state+0x1fc/0x398
[ 67.330764] cpuidle_enter+0x18/0x20
[ 67.330772] do_idle+0x1b4/0x290
[ 67.330778] cpu_startup_entry+0x20/0x28
[ 67.330786] secondary_start_kernel+0x160/0x170

Fix this by:
1) Establishing pointers to 'struct dm_io' members in
dm_io_dec_pending() so that they may be passed into end_io_acct()
_after_ free_io() is called.
2) Moving end_io_acct() after free_io().

En el kernel de Linux, se resolvió la siguiente vulnerabilidad: dm: corrige la ejecución del puntero NULL de mempool al completar IO dm_io_dec_pending() llama a end_io_acct() primero y luego dec md en vuelo conteo pendiente. Pero si una tarea intercambia la tabla DM al mismo tiempo, esto puede provocar un bloqueo debido a que mempool->elementos son NULL: tarea1 tarea2 do_resume ->do_suspend ->dm_wait_for_completion bio_endio ->clone_endio ->dm_io_dec_pending ->end_io_acct ->wakeup task1 - >dm_swap_table ->__bind ->__bind_mempools ->bioset_exit ->mempool_exit ->free_io [67.330330] No se puede manejar la desreferencia del puntero NULL del kernel en la dirección virtual 00000000000000000 ...... [67.330494] pstate: 80400085 (Nzcv daIf +PAN -UAO ) [67.330510] pc: mempool_free+0x70/0xa0 [67.330515] lr: mempool_free+0x4c/0xa0 [67.330520] sp: ffffff8008013b20 [67.330524] x29: ffffff8008013b20 x28: 000000000000004 [ 67.330530] x27: fffffa8c2ff40a0 x26: 00000000ffff1cc8 [ 67.330535] x25: 0000000000000000 x24: ffffffdada34c800 [ 67.330541] x23: 0000000000000000 x22: ffffffdada34c800 [ 67.330547] x21: 00000000ffff1cc8 x20: 1304d80 [ 67.330552] x19: ffffffdada34c970 x18: 000000b312625d9c [ 67.330558] x17: 00000000002dcfbf x16: 00000000000006dd [ 67.330563] 000000000093b41e x14: 0000000000000010 [ 67.330569] x13: 0000000000007f7a x12: 0000000034155555 [ 67.330574] x11: 00000000000000001 x10: 0000000000000001 [ 67.330579] x9 : 0000000000000000 x8: 0000000000000000 [67.330585] x7: 0000000000000000 x6: ffffff80148b5c1a [67.330590] x5: ffffff8008013ae0 x4: 000000001 [67.330596] x3: ffffff80080139c8 x2: ffffff801083bab8 [67.330601] x1: 0000000000000000 x0: ffffffdada34c970 [67.330609] Rastreo de llamadas: [67.330616] mempool_free+0x70/0xa0 [67.330627] 8/0x110 [67.330638] dec_pending+0x13c/0x230 [67.330644] clone_endio+0x90/0x180 [ 67.330649] bio_endio+0x198/0x1b8 [ 67.330655] dec_pending+0x190/0x230 [ 67.330660] clone_endio+0x90/0x180 [ 67.330665] bio_endio+0x198/0x1b8 [ 67.330673 ] blk_update_request+0x214/0x428 [ 67.330683] scsi_end_request+0x2c/0x300 [ 67.330688 ] scsi_io_completion+0xa0/0x710 [ 67.330695] scsi_finish_command+0xd8/0x110 [ 67.330700] scsi_softirq_done+0x114/0x148 [ 67.330708] blk_done_softirq+0x74/0xd0 [ 67.3307 16] __do_softirq+0x18c/0x374 [ 67.330724] irq_exit+0xb4/0xb8 [ 67.330732] __handle_domain_irq +0x84/0xc0 [ 67.330737] gic_handle_irq+0x148/0x1b0 [ 67.330744] el1_irq+0xe8/0x190 [ 67.330753] lpm_cpuidle_enter+0x4f8/0x538 [ 67.330759] +0x1fc/0x398 [ 67.330764] cpuidle_enter+0x18/0x20 [ 67.330772] do_idle+0x1b4 /0x290 [ 67.330778] cpu_startup_entry+0x20/0x28 [ 67.330786] second_start_kernel+0x160/0x170 Solucione este problema de la siguiente manera: 1) Estableciendo punteros a los miembros 'struct dm_io' en dm_io_dec_pending() para que puedan pasarse a end_io_acct() _después_ free_io() se llama. 2) Mover end_io_acct() después de free_io().

*Credits: N/A

CVSS Scores

Red Hatv3.1 5.5

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

* Common Vulnerability Scoring System

SSVC

Decision:Track

Exploitation

None

Automatable

Tech. Impact

Partial

* Organization's Worst-case Scenario

Timeline

2024-05-21 CVE Reserved
2024-05-22 CVE Published
2024-05-22 EPSS Updated
2024-11-04 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-476: NULL Pointer Dereference

CAPEC

References (9)

URL	Tag	Source

URL	Date	SRC

URL	Date	SRC
https://git.kernel.org/stable/c/9fb7cd5c7fef0f1c982e3cd27745a0dec260eaed	2022-05-12
https://git.kernel.org/stable/c/d35aef9c60d310eff3eaddacce301efe877e2b7c	2022-05-12
https://git.kernel.org/stable/c/9e07272cca2ed76f7f6073f4444b1143828c8d87	2022-05-12
https://git.kernel.org/stable/c/ad1393b92e5059218d055bfec8f4946d85ad04c4	2022-05-12
https://git.kernel.org/stable/c/d29c78d3f9c5d2604548c1065bf1ec212728ea61	2022-04-27
https://git.kernel.org/stable/c/6e506f07c5b561d673dd0b0d8f7f420cc48024fb	2021-10-20
https://git.kernel.org/stable/c/d208b89401e073de986dc891037c5a668f5d5d95	2021-10-12

URL	Date	SRC
https://access.redhat.com/security/cve/CVE-2021-47435	2022-07-19
https://bugzilla.redhat.com/show_bug.cgi?id=2282879	2022-07-19

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"				< 4.9.313 Search vendor "Linux" for product "Linux Kernel" and version " < 4.9.313"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 4.14.278 Search vendor "Linux" for product "Linux Kernel" and version " < 4.14.278"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 4.19.242 Search vendor "Linux" for product "Linux Kernel" and version " < 4.19.242"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 5.4.193 Search vendor "Linux" for product "Linux Kernel" and version " < 5.4.193"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 5.10.113 Search vendor "Linux" for product "Linux Kernel" and version " < 5.10.113"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 5.14.14 Search vendor "Linux" for product "Linux Kernel" and version " < 5.14.14"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				< 5.15 Search vendor "Linux" for product "Linux Kernel" and version " < 5.15"		en		Affected