CVE-2021-47572

net: nexthop: fix null pointer dereference when IPv6 is not enabled

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:

net: nexthop: fix null pointer dereference when IPv6 is not enabled

When we try to add an IPv6 nexthop and IPv6 is not enabled
(!CONFIG_IPV6) we'll hit a NULL pointer dereference[1] in the error path
of nh_create_ipv6() due to calling ipv6_stub->fib6_nh_release. The bug
has been present since the beginning of IPv6 nexthop gateway support.
Commit 1aefd3de7bc6 ("ipv6: Add fib6_nh_init and release to stubs") tells
us that only fib6_nh_init has a dummy stub because fib6_nh_release should
not be called if fib6_nh_init returns an error, but the commit below added
a call to ipv6_stub->fib6_nh_release in its error path. To fix it return
the dummy stub's -EAFNOSUPPORT error directly without calling
ipv6_stub->fib6_nh_release in nh_create_ipv6()'s error path.

[1]
Output is a bit truncated, but it clearly shows the error.
BUG: kernel NULL pointer dereference, address: 000000000000000000
#PF: supervisor instruction fetch in kernel modede
#PF: error_code(0x0010) - not-present pagege
PGD 0 P4D 0
Oops: 0010 [#1] PREEMPT SMP NOPTI
CPU: 4 PID: 638 Comm: ip Kdump: loaded Not tainted 5.16.0-rc1+ #446
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 04/01/2014
RIP: 0010:0x0
Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6.
RSP: 0018:ffff888109f5b8f0 EFLAGS: 00010286^Ac
RAX: 0000000000000000 RBX: ffff888109f5ba28 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8881008a2860
RBP: ffff888109f5b9d8 R08: 0000000000000000 R09: 0000000000000000
R10: ffff888109f5b978 R11: ffff888109f5b948 R12: 00000000ffffff9f
R13: ffff8881008a2a80 R14: ffff8881008a2860 R15: ffff8881008a2840
FS: 00007f98de70f100(0000) GS:ffff88822bf00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 0000000100efc000 CR4: 00000000000006e0
Call Trace:
<TASK>
nh_create_ipv6+0xed/0x10c
rtm_new_nexthop+0x6d7/0x13f3
? check_preemption_disabled+0x3d/0xf2
? lock_is_held_type+0xbe/0xfd
rtnetlink_rcv_msg+0x23f/0x26a
? check_preemption_disabled+0x3d/0xf2
? rtnl_calcit.isra.0+0x147/0x147
netlink_rcv_skb+0x61/0xb2
netlink_unicast+0x100/0x187
netlink_sendmsg+0x37f/0x3a0
? netlink_unicast+0x187/0x187
sock_sendmsg_nosec+0x67/0x9b
____sys_sendmsg+0x19d/0x1f9
? copy_msghdr_from_user+0x4c/0x5e
? rcu_read_lock_any_held+0x2a/0x78
___sys_sendmsg+0x6c/0x8c
? asm_sysvec_apic_timer_interrupt+0x12/0x20
? lockdep_hardirqs_on+0xd9/0x102
? sockfd_lookup_light+0x69/0x99
__sys_sendmsg+0x50/0x6e
do_syscall_64+0xcb/0xf2
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f98dea28914
Code: 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b5 0f 1f 80 00 00 00 00 48 8d 05 e9 5d 0c 00 8b 00 85 c0 75 13 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 41 54 41 89 d4 55 48 89 f5 53
RSP: 002b:00007fff859f5e68 EFLAGS: 00000246 ORIG_RAX: 000000000000002e2e
RAX: ffffffffffffffda RBX: 00000000619cb810 RCX: 00007f98dea28914
RDX: 0000000000000000 RSI: 00007fff859f5ed0 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000008
R10: fffffffffffffce6 R11: 0000000000000246 R12: 0000000000000001
R13: 000055c0097ae520 R14: 000055c0097957fd R15: 00007fff859f63a0
</TASK>
Modules linked in: bridge stp llc bonding virtio_net

En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: net: nexthop: corrige la desreferencia del puntero nulo cuando IPv6 no está habilitado Cuando intentamos agregar un nexthop IPv6 y IPv6 no está habilitado (!CONFIG_IPV6) alcanzaremos una desreferencia del puntero NULL [1] en la ruta de error de nh_create_ipv6() debido a la llamada a ipv6_stub->fib6_nh_release. El error ha estado presente desde el comienzo del soporte de la puerta de enlace IPv6 nexthop. El commit 1aefd3de7bc6 ("ipv6: Agregar fib6_nh_init y liberar a los stubs") nos dice que solo fib6_nh_init tiene un stub ficticio porque no se debe llamar a fib6_nh_release si fib6_nh_init devuelve un error, pero el commit a continuación agregó una llamada a ipv6_stub->fib6_nh_release en su error camino. Para solucionarlo, devuelva el error -EAFNOSUPPORT del código auxiliar ficticio directamente sin llamar a ipv6_stub->fib6_nh_release en la ruta de error de nh_create_ipv6(). [1] La salida está un poco truncada, pero muestra claramente el error. ERROR: desreferencia del puntero NULL del kernel, dirección: 0000000000000000000 #PF: búsqueda de instrucciones del supervisor en modo kernel #PF: código_error(0x0010) - página no presente PGD 0 P4D 0 Ups: 0010 [#1] PREEMPT SMP NOPTI CPU: 4 PID: 638 Comm: ip Kdump: cargado No contaminado 5.16.0-rc1+ #446 Nombre del hardware: PC estándar QEMU (i440FX + PIIX, 1996), BIOS 1.14.0-4.fc34 01/04/2014 RIP: 0010:0x0 Código: No se puede acceder a los bytes del código de operación en RIP 0xffffffffffffffd6. RSP: 0018:ffff888109f5b8f0 EFLAGS: 00010286^Ac RAX: 0000000000000000 RBX: ffff888109f5ba28 RCX: 00000000000000000 RDX: 0000000000000000 RSI: 000000000000000 RDI: ffff8881008a2860 RBP: ffff888109f5b9d8 R08: 0000000000000000 R09: 00000000000000000 R10: ffff888109f5b978 R11: 9f5b948 R12: 00000000ffffff9f R13: ffff8881008a2a80 R14 : ffff8881008a2860 R15: ffff8881008a2840 FS: 00007f98de70f100(0000) GS:ffff88822bf00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0 CR0: 0000000080050033 CR2: ffffffffffffffd6 CR3: 0000000100efc000 CR4: 00000000000006e0 Seguimiento de llamadas: nh_create_ipv6+0xed /0x10c rtm_new_nexthop+0x6d7/0x13f3 ? check_preemption_disabled+0x3d/0xf2? lock_is_held_type+0xbe/0xfd rtnetlink_rcv_msg+0x23f/0x26a? check_preemption_disabled+0x3d/0xf2? rtnl_calcit.isra.0+0x147/0x147 netlink_rcv_skb+0x61/0xb2 netlink_unicast+0x100/0x187 netlink_sendmsg+0x37f/0x3a0 ? netlink_unicast+0x187/0x187 sock_sendmsg_nosec+0x67/0x9b ____sys_sendmsg+0x19d/0x1f9 ? copy_msghdr_from_user+0x4c/0x5e? rcu_read_lock_any_held+0x2a/0x78 ___sys_sendmsg+0x6c/0x8c? asm_sysvec_apic_timer_interrupt+0x12/0x20? lockdep_hardirqs_on+0xd9/0x102? sockfd_lookup_light+0x69/0x99 __sys_sendmsg+0x50/0x6e do_syscall_64+0xcb/0xf2 Entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f98dea28914 Código: 00 f7 d8 64 89 02 c7 c0 ff ff ff ff eb b5 0f 1f 80 00 00 00 00 48 8d 05 e9 5d 0c 00 8b 00 85 c0 75 13 b8 2e 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 54 c3 0f 1f 00 41 54 41 89 d4 55 48 89 f5 53 RSP: :00007fff859f5e68 EFLAGS: 00000246 ORIG_RAX: 000000000000002e2e RAX: ffffffffffffffda RBX: 00000000619cb810 RCX: 00007f98dea28914 RDX: 0000000000000000 RSI: 00007fff859f5ed0 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000008 R10: fffffffffffffce6 R11: 0000000000000246 R12: 0000000000001 R13: 000055c0097ae520 R14: 000055c0097957fd R15: 00007fff859f63a0 < /TASK> Módulos vinculados en: bridge stp llc bonding virtio_net

*Credits: N/A

CVSS Scores

NISTv3.1 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

2024-05-24 CVE Reserved
2024-05-24 CVE Published
2024-06-11 EPSS Updated
2024-12-19 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-476: NULL Pointer Dereference

CAPEC

References (5)

URL	Tag	Source
https://git.kernel.org/stable/c/53010f991a9f5e4ed2db705ddde6ff32709192a2	Vuln. Introduced

URL	Date	SRC

URL	Date	SRC
https://git.kernel.org/stable/c/7b6f44856da5ba0b1aa61403eb9fddd272156503	2021-12-01
https://git.kernel.org/stable/c/b70ff391deeec35cdd8a05f5f63f5fe28bc4f225	2021-12-01
https://git.kernel.org/stable/c/39509d76a9a3d02f379d52cb4b1449469c56c0e0	2021-12-01
https://git.kernel.org/stable/c/1c743127cc54b112b155f434756bd4b5fa565a99	2021-11-23

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"				>= 5.3 < 5.4.163 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.3 < 5.4.163"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.3 < 5.10.83 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.3 < 5.10.83"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.3 < 5.15.6 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.3 < 5.15.6"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.3 < 5.16 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.3 < 5.16"		en		Affected