CVE-2021-46954

net/sched: sch_frag: fix stack OOB read while fragmenting IPv4 packets

Severity Score

7.1

*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/sched: sch_frag: fix stack OOB read while fragmenting IPv4 packets

when 'act_mirred' tries to fragment IPv4 packets that had been previously
re-assembled using 'act_ct', splats like the following can be observed on
kernels built with KASAN:

BUG: KASAN: stack-out-of-bounds in ip_do_fragment+0x1b03/0x1f60
Read of size 1 at addr ffff888147009574 by task ping/947

CPU: 0 PID: 947 Comm: ping Not tainted 5.12.0-rc6+ #418
Hardware name: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 04/01/2014
Call Trace:
<IRQ>
dump_stack+0x92/0xc1
print_address_description.constprop.7+0x1a/0x150
kasan_report.cold.13+0x7f/0x111
ip_do_fragment+0x1b03/0x1f60
sch_fragment+0x4bf/0xe40
tcf_mirred_act+0xc3d/0x11a0 [act_mirred]
tcf_action_exec+0x104/0x3e0
fl_classify+0x49a/0x5e0 [cls_flower]
tcf_classify_ingress+0x18a/0x820
__netif_receive_skb_core+0xae7/0x3340
__netif_receive_skb_one_core+0xb6/0x1b0
process_backlog+0x1ef/0x6c0
__napi_poll+0xaa/0x500
net_rx_action+0x702/0xac0
__do_softirq+0x1e4/0x97f
do_softirq+0x71/0x90
</IRQ>
__local_bh_enable_ip+0xdb/0xf0
ip_finish_output2+0x760/0x2120
ip_do_fragment+0x15a5/0x1f60
__ip_finish_output+0x4c2/0xea0
ip_output+0x1ca/0x4d0
ip_send_skb+0x37/0xa0
raw_sendmsg+0x1c4b/0x2d00
sock_sendmsg+0xdb/0x110
__sys_sendto+0x1d7/0x2b0
__x64_sys_sendto+0xdd/0x1b0
do_syscall_64+0x33/0x40
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f82e13853eb
Code: 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 f3 0f 1e fa 48 8d 05 75 42 2c 00 41 89 ca 8b 00 85 c0 75 14 b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 75 c3 0f 1f 40 00 41 57 4d 89 c7 41 56 41 89
RSP: 002b:00007ffe01fad888 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00005571aac13700 RCX: 00007f82e13853eb
RDX: 0000000000002330 RSI: 00005571aac13700 RDI: 0000000000000003
RBP: 0000000000002330 R08: 00005571aac10500 R09: 0000000000000010
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe01faefb0
R13: 00007ffe01fad890 R14: 00007ffe01fad980 R15: 00005571aac0f0a0

The buggy address belongs to the page:
page:000000001dff2e03 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x147009
flags: 0x17ffffc0001000(reserved)
raw: 0017ffffc0001000 ffffea00051c0248 ffffea00051c0248 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff888147009400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888147009480: f1 f1 f1 f1 04 f2 f2 f2 f2 f2 f2 f2 00 00 00 00
>ffff888147009500: 00 00 00 00 00 00 00 00 00 00 f2 f2 f2 f2 f2 f2
^
ffff888147009580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888147009600: 00 00 00 00 00 00 00 00 00 00 00 00 00 f2 f2 f2

for IPv4 packets, sch_fragment() uses a temporary struct dst_entry. Then,
in the following call graph:

ip_do_fragment()
ip_skb_dst_mtu()
ip_dst_mtu_maybe_forward()
ip_mtu_locked()

the pointer to struct dst_entry is used as pointer to struct rtable: this
turns the access to struct members like rt_mtu_locked into an OOB read in
the stack. Fix this changing the temporary variable used for IPv4 packets
in sch_fragment(), similarly to what is done for IPv6 few lines below.

En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: net/sched: sch_frag: corrige la lectura OOB de la pila al fragmentar paquetes IPv4 cuando 'act_mirred' intenta fragmentar paquetes IPv4 que se habían reensamblado previamente usando 'act_ct', símbolos como el Se puede observar lo siguiente en los núcleos creados con KASAN: ERROR: KASAN: pila fuera de los límites en ip_do_fragment+0x1b03/0x1f60 Lectura de tamaño 1 en la dirección ffff888147009574 mediante tarea ping/947 CPU: 0 PID: 947 Comm: ping no contaminado 5.12.0-rc6+ #418 Nombre de hardware: Red Hat KVM, BIOS 1.11.1-4.module+el8.1.0+4066+0f1aadab 01/04/2014 Seguimiento de llamadas: dump_stack+0x92/0xc1 print_address_description.constprop. 7+0x1a/0x150 kasan_report.cold.13+0x7f/0x111 ip_do_fragment+0x1b03/0x1f60 sch_fragment+0x4bf/0xe40 tcf_mirred_act+0xc3d/0x11a0 [act_mirred] tcf_action_exec+0x104/0x3e0 fl_classify+0 x49a/0x5e0 [cls_flower] tcf_classify_ingress+0x18a/0x820 __netif_receive_skb_core+0xae7/0x3340 __netif_receive_skb_one_core+0xb6/0x1b0 Process_backlog+0x1ef/0x6c0 __napi_poll+0xaa/0x500 net_rx_action+0x702/0xac0 __do_softirq+0x1e4/0x97f do_softirq +0x71/0x90 __local_bh_enable_ip+0xdb/0xf0 ip_finish_output2+0x760/0x2120 ip_do_fragment +0x15a5/0x1f60 __ip_finish_output+0x4c2/0xea0 ip_output+0x1ca/0x4d0 ip_send_skb+0x37/0xa0 raw_sendmsg+0x1c4b/0x2d00 sock_sendmsg+0xdb/0x110 __sys_sendto+0x1d7/0x 2b0 __x64_sys_sendto+0xdd/0x1b0 do_syscall_64+0x33/0x40 Entry_SYSCALL_64_after_hwframe+0x44/0xae RIP : 0033:0x7f82e13853eb Código: 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 f3 0f 1e fa 48 8d 05 75 42 2c 00 41 89 ca 8b 00 85 c0 75 14 b8 2c 00 00 00 0f 05 <48 > 3d 00 f0 ff ff 77 75 c3 0f 1f 40 00 41 57 4d 89 c7 41 56 41 89 RSP: 002b:00007ffe01fad888 EFLAGS: 00000246 ORIG_RAX: 000000000000002c RAX: ffff ffffffffffda RBX: 00005571aac13700 RCX: 00007f82e13853eb RDX: 0000000000002330 RSI: 00005571aac13700 RDI: 0000000000000003 RBP: 0000000000002330 R08: 00005571aac10500 R09: 0000000000000010 R10: 00000000000000000 R11: 0000000000000246 R12: 00007ffe01faefb0 R13: 00007ffe01fad890 R14: 00007ffe01fad980 R15: 00005571aac0f0a0 La dirección del error pertenece a la página: página:000000001dff2e03 refcount:1 mapcount:0 mapeo:0000000000000000 índice: 0x0 pfn:0x147009 banderas: 0x17ffffc0001000(reservado) raw: 0017ffffc0001000 ffffea00051c0248 ffffea00051c0248 0000000000000000 raw: 0000000000000000 0000 000000000000 00000001ffffffff 00000000000000000 página volcada porque: kasan: se detectó mal acceso Estado de la memoria alrededor de la dirección con errores: ffff888147009400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888147009480: f1 f1 f1 f1 04 f2 f2 f2 f2 f2 f2 f2 00 00 00 00 >ffff888147009500: 00 00 00 00 00 00 00 00 00 00 f2 f2 f2 f 2 f2 f2^ffff888147009580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff888147009600: 00 00 00 00 00 00 00 00 00 00 00 00 00 f2 f2 f2 para paquetes IPv4, sch_fragment() utiliza una estructura temporal dst_entry. Luego, en el siguiente gráfico de llamadas: ip_do_fragment() ip_skb_dst_mtu() ip_dst_mtu_maybe_forward() ip_mtu_locked() el puntero a struct dst_entry se usa como puntero a struct rtable: esto convierte el acceso a miembros de estructura como rt_mtu_locked en una lectura OOB en la pila. Solucione este problema cambiando la variable temporal utilizada para los paquetes IPv4 en sch_fragment(), de manera similar a lo que se hace para IPv6 unas líneas más abajo.

*Credits: N/A

CVSS Scores

NISTv3.1 7.1

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

High

* 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
2024-04-21 EPSS Updated
2024-08-04 CVE Updated
---------- Exploited in Wild
---------- KEV Due Date
---------- First Exploit

CWE

CWE-125: Out-of-bounds Read

CAPEC

References (4)

URL	Tag	Source
https://git.kernel.org/stable/c/c129412f74e99b609f0a8e95fc3915af1fd40f34	Vuln. Introduced

URL	Date	SRC

URL	Date	SRC
https://git.kernel.org/stable/c/018bb8da5b5888e19585f9b802f036afe643fcef	2021-05-12
https://git.kernel.org/stable/c/8e6dfb7beeb6489ac1365b8a71052e737f5da76e	2021-05-12
https://git.kernel.org/stable/c/31fe34a0118e0acc958c802e830ad5d37ef6b1d3	2021-04-29

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"				>= 5.11 < 5.11.20 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.11 < 5.11.20"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.11 < 5.12.3 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.11 < 5.12.3"		en		Affected
Linux Search vendor "Linux"		Linux Kernel Search vendor "Linux" for product "Linux Kernel"				>= 5.11 < 5.13 Search vendor "Linux" for product "Linux Kernel" and version " >= 5.11 < 5.13"		en		Affected