CVE-2021-46981

nbd: Fix NULL pointer in flush_workqueue

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:

nbd: Fix NULL pointer in flush_workqueue

Open /dev/nbdX first, the config_refs will be 1 and
the pointers in nbd_device are still null. Disconnect
/dev/nbdX, then reference a null recv_workq. The
protection by config_refs in nbd_genl_disconnect is useless.

[ 656.366194] BUG: kernel NULL pointer dereference, address: 0000000000000020
[ 656.368943] #PF: supervisor write access in kernel mode
[ 656.369844] #PF: error_code(0x0002) - not-present page
[ 656.370717] PGD 10cc87067 P4D 10cc87067 PUD 1074b4067 PMD 0
[ 656.371693] Oops: 0002 [#1] SMP
[ 656.372242] CPU: 5 PID: 7977 Comm: nbd-client Not tainted 5.11.0-rc5-00040-g76c057c84d28 #1
[ 656.373661] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014
[ 656.375904] RIP: 0010:mutex_lock+0x29/0x60
[ 656.376627] Code: 00 0f 1f 44 00 00 55 48 89 fd 48 83 05 6f d7 fe 08 01 e8 7a c3 ff ff 48 83 05 6a d7 fe 08 01 31 c0 65 48 8b 14 25 00 6d 01 00 <f0> 48 0f b1 55 d
[ 656.378934] RSP: 0018:ffffc900005eb9b0 EFLAGS: 00010246
[ 656.379350] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
[ 656.379915] RDX: ffff888104cf2600 RSI: ffffffffaae8f452 RDI: 0000000000000020
[ 656.380473] RBP: 0000000000000020 R08: 0000000000000000 R09: ffff88813bd6b318
[ 656.381039] R10: 00000000000000c7 R11: fefefefefefefeff R12: ffff888102710b40
[ 656.381599] R13: ffffc900005eb9e0 R14: ffffffffb2930680 R15: ffff88810770ef00
[ 656.382166] FS: 00007fdf117ebb40(0000) GS:ffff88813bd40000(0000) knlGS:0000000000000000
[ 656.382806] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 656.383261] CR2: 0000000000000020 CR3: 0000000100c84000 CR4: 00000000000006e0
[ 656.383819] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 656.384370] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[ 656.384927] Call Trace:
[ 656.385111] flush_workqueue+0x92/0x6c0
[ 656.385395] nbd_disconnect_and_put+0x81/0xd0
[ 656.385716] nbd_genl_disconnect+0x125/0x2a0
[ 656.386034] genl_family_rcv_msg_doit.isra.0+0x102/0x1b0
[ 656.386422] genl_rcv_msg+0xfc/0x2b0
[ 656.386685] ? nbd_ioctl+0x490/0x490
[ 656.386954] ? genl_family_rcv_msg_doit.isra.0+0x1b0/0x1b0
[ 656.387354] netlink_rcv_skb+0x62/0x180
[ 656.387638] genl_rcv+0x34/0x60
[ 656.387874] netlink_unicast+0x26d/0x590
[ 656.388162] netlink_sendmsg+0x398/0x6c0
[ 656.388451] ? netlink_rcv_skb+0x180/0x180
[ 656.388750] ____sys_sendmsg+0x1da/0x320
[ 656.389038] ? ____sys_recvmsg+0x130/0x220
[ 656.389334] ___sys_sendmsg+0x8e/0xf0
[ 656.389605] ? ___sys_recvmsg+0xa2/0xf0
[ 656.389889] ? handle_mm_fault+0x1671/0x21d0
[ 656.390201] __sys_sendmsg+0x6d/0xe0
[ 656.390464] __x64_sys_sendmsg+0x23/0x30
[ 656.390751] do_syscall_64+0x45/0x70
[ 656.391017] entry_SYSCALL_64_after_hwframe+0x44/0xa9

To fix it, just add if (nbd->recv_workq) to nbd_disconnect_and_put().

En el kernel de Linux, se resolvió la siguiente vulnerabilidad: nbd: corrija el puntero NULL en flush_workqueue Abra /dev/nbdX primero, config_refs será 1 y los punteros en nbd_device seguirán siendo nulos. Desconecte /dev/nbdX, luego haga referencia a un recv_workq nulo. La protección de config_refs en nbd_genl_disconnect es inútil. [656.366194] ERROR: desreferencia del puntero NULL del kernel, dirección: 00000000000000020 [656.368943] #PF: acceso de escritura del supervisor en modo kernel [656.369844] #PF: código_error(0x0002) - página no presente [656.370717] PGD 10cc87067 P 4D 10cc87067 PUD 1074b4067 PMD 0 [656.371693] Ups: 0002 [#1] SMP [656.372242] CPU: 5 PID: 7977 Comm: nbd-client No contaminado 5.11.0-rc5-00040-g76c057c84d28 #1 [656.373661] Nombre de hardware: PC estándar QEMU (i 440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 01/04/2014 [ 656.375904] RIP: 0010:mutex_lock+0x29/0x60 [ 656.376627] Código: 00 0f 1f 44 00 00 55 48 89 fd 48 83 05 6f d7 fe 08 01 e8 7a c3 ff ff 48 83 05 6a d7 fe 08 01 31 c0 65 48 8b 14 25 00 6d 01 00 48 0f b1 55 d [ 656.378934 ] RSP: 0018:ffffc900005eb9b0 EFLAGS: 00010246 [ 656.379350] RAX: 0000000000000000 RBX: 00000000000000000 RCX: 0000000000000000 [ 656.379915 ] RDX: ffff888104cf2600 RSI: fffffffaae8f452 RDI: 0000000000000020 [ 656.380473] RBP: 00000000000000020 R08: 00000000000000000 R09: ffff88813bd6b31 8 [656.381039] R10: 00000000000000c7 R11: fefefefefefefeff R12: ffff888102710b40 [ 656.381599] R13: ffffc900005eb9e0 R14: ffffffffb2930680 R15: ffff88810770ef00 [ 656.3821 66] FS: 00007fdf117ebb40(0000) GS:ffff88813bd40000(0000) knlGS:0000000000000000 [ 656.382806] CS: 0010 DS: 0000 ES: 0000 CR0 : 0000000080050033 [ 656.383261] CR2: 0000000000000020 CR3: 0000000100c84000 CR4: 00000000000006e0 [ 656.383819] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 656.384370] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 656.384927] Seguimiento de llamadas : [656.385111] flux_workqueue+0x92 /0x6c0 [ 656.385395] nbd_disconnect_and_put+0x81/0xd0 [ 656.385716] nbd_genl_disconnect+0x125/0x2a0 [ 656.386034] genl_family_rcv_msg_doit.isra.0+0x102/0x1b0 [ 656 .386422] genl_rcv_msg+0xfc/0x2b0 [656.386685]? nbd_ioctl+0x490/0x490 [656.386954]? genl_family_rcv_msg_doit.isra.0+0x1b0/0x1b0 [ 656.387354] netlink_rcv_skb+0x62/0x180 [ 656.387638] genl_rcv+0x34/0x60 [ 656.387874] netlink_unicast+0x26d/0x590 [ 6 56.388162] netlink_sendmsg+0x398/0x6c0 [656.388451]? netlink_rcv_skb+0x180/0x180 [656.388750] ____sys_sendmsg+0x1da/0x320 [656.389038] ? ____sys_recvmsg+0x130/0x220 [ 656.389334] ___sys_sendmsg+0x8e/0xf0 [ 656.389605] ? ___sys_recvmsg+0xa2/0xf0 [656.389889] ? handle_mm_fault+0x1671/0x21d0 [ 656.390201] __sys_sendmsg+0x6d/0xe0 [ 656.390464] __x64_sys_sendmsg+0x23/0x30 [ 656.390751] do_syscall_64+0x45/0x70 [656.391017] Entry_SYSCALL_64_after_hwframe+0x44/0xa9 Para solucionarlo, simplemente agregue if (nbd->recv_workq) a nbd_disconnect_and_put().

*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
2024-02-28 CVE Published
2024-12-17 EPSS Updated
2024-12-19 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CAPEC

References (12)

URL	Tag	Source
https://git.kernel.org/stable/c/e9e006f5fcf2bab59149cb38a48a4817c1b538b4	Vuln. Introduced
https://git.kernel.org/stable/c/0b584bf573ae59021069c056c22d65d5721910cb	Vuln. Introduced
https://git.kernel.org/stable/c/d1db913b044f0a0693d8ee283d26b81d536efcd5	Vuln. Introduced
https://git.kernel.org/stable/c/9f0f39c92e4f50189155dfb13bb5524372e40eba	Vuln. Introduced
https://git.kernel.org/stable/c/e83a26a49356a3dbd4f54102abe17fc594643698	Vuln. Introduced
https://git.kernel.org/stable/c/92ec11cccb7fc14331e000ab2337f60aa433433e	Vuln. Introduced
https://git.kernel.org/stable/c/b3ead320dce6c7d7206103deca766b317591c286	Vuln. Introduced

URL	Date	SRC

URL	Date	SRC
https://git.kernel.org/stable/c/1c4962df938891af9ab4775f5224ef8601764107	2021-05-19
https://git.kernel.org/stable/c/cde4b55cfb24522dcbba80bbdb0c082303e76c43	2021-05-19
https://git.kernel.org/stable/c/b31d237796fd618379ec8e0f4de3370b5e4aeee7	2021-05-19
https://git.kernel.org/stable/c/54b78ba7e96e5fe1edb8054e375d31a6c0dc60dc	2021-05-19
https://git.kernel.org/stable/c/79ebe9110fa458d58f1fceb078e2068d7ad37390	2021-05-12

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"				>= 5.4 < 5.4.120 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 5.4.120"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.4 < 5.10.38 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 5.10.38"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.4 < 5.11.22 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 5.11.22"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.4 < 5.12.5 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 5.12.5"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.4 < 5.13 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.4 < 5.13"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				4.14.149 Search vendor "Linux" for product "Linux Kernel" and version "4.14.149"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				4.14.161 Search vendor "Linux" for product "Linux Kernel" and version "4.14.161"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				4.19.79 Search vendor "Linux" for product "Linux Kernel" and version "4.19.79"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				4.19.92 Search vendor "Linux" for product "Linux Kernel" and version "4.19.92"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				5.3.6 Search vendor "Linux" for product "Linux Kernel" and version "5.3.6"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				5.4.7 Search vendor "Linux" for product "Linux Kernel" and version "5.4.7"		en		Affected