// For flags

CVE-2021-47099

veth: ensure skb entering GRO are not cloned.

Severity Score

6.0
*CVSS v3.1

Exploit Likelihood

*EPSS

Affected Versions

*CPE

Public Exploits

0
*Multiple Sources

Exploited in Wild

-
*KEV

Decision

Track
*SSVC
Descriptions

In the Linux kernel, the following vulnerability has been resolved:

veth: ensure skb entering GRO are not cloned.

After commit d3256efd8e8b ("veth: allow enabling NAPI even without XDP"),
if GRO is enabled on a veth device and TSO is disabled on the peer
device, TCP skbs will go through the NAPI callback. If there is no XDP
program attached, the veth code does not perform any share check, and
shared/cloned skbs could enter the GRO engine.

Ignat reported a BUG triggered later-on due to the above condition:

[ 53.970529][ C1] kernel BUG at net/core/skbuff.c:3574!
[ 53.981755][ C1] invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
[ 53.982634][ C1] CPU: 1 PID: 19 Comm: ksoftirqd/1 Not tainted 5.16.0-rc5+ #25
[ 53.982634][ C1] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
[ 53.982634][ C1] RIP: 0010:skb_shift+0x13ef/0x23b0
[ 53.982634][ C1] Code: ea 03 0f b6 04 02 48 89 fa 83 e2 07 38 d0
7f 08 84 c0 0f 85 41 0c 00 00 41 80 7f 02 00 4d 8d b5 d0 00 00 00 0f
85 74 f5 ff ff <0f> 0b 4d 8d 77 20 be 04 00 00 00 4c 89 44 24 78 4c 89
f7 4c 89 8c
[ 53.982634][ C1] RSP: 0018:ffff8881008f7008 EFLAGS: 00010246
[ 53.982634][ C1] RAX: 0000000000000000 RBX: ffff8881180b4c80 RCX: 0000000000000000
[ 53.982634][ C1] RDX: 0000000000000002 RSI: ffff8881180b4d3c RDI: ffff88810bc9cac2
[ 53.982634][ C1] RBP: ffff8881008f70b8 R08: ffff8881180b4cf4 R09: ffff8881180b4cf0
[ 53.982634][ C1] R10: ffffed1022999e5c R11: 0000000000000002 R12: 0000000000000590
[ 53.982634][ C1] R13: ffff88810f940c80 R14: ffff88810f940d50 R15: ffff88810bc9cac0
[ 53.982634][ C1] FS: 0000000000000000(0000) GS:ffff888235880000(0000) knlGS:0000000000000000
[ 53.982634][ C1] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 53.982634][ C1] CR2: 00007ff5f9b86680 CR3: 0000000108ce8004 CR4: 0000000000170ee0
[ 53.982634][ C1] Call Trace:
[ 53.982634][ C1] <TASK>
[ 53.982634][ C1] tcp_sacktag_walk+0xaba/0x18e0
[ 53.982634][ C1] tcp_sacktag_write_queue+0xe7b/0x3460
[ 53.982634][ C1] tcp_ack+0x2666/0x54b0
[ 53.982634][ C1] tcp_rcv_established+0x4d9/0x20f0
[ 53.982634][ C1] tcp_v4_do_rcv+0x551/0x810
[ 53.982634][ C1] tcp_v4_rcv+0x22ed/0x2ed0
[ 53.982634][ C1] ip_protocol_deliver_rcu+0x96/0xaf0
[ 53.982634][ C1] ip_local_deliver_finish+0x1e0/0x2f0
[ 53.982634][ C1] ip_sublist_rcv_finish+0x211/0x440
[ 53.982634][ C1] ip_list_rcv_finish.constprop.0+0x424/0x660
[ 53.982634][ C1] ip_list_rcv+0x2c8/0x410
[ 53.982634][ C1] __netif_receive_skb_list_core+0x65c/0x910
[ 53.982634][ C1] netif_receive_skb_list_internal+0x5f9/0xcb0
[ 53.982634][ C1] napi_complete_done+0x188/0x6e0
[ 53.982634][ C1] gro_cell_poll+0x10c/0x1d0
[ 53.982634][ C1] __napi_poll+0xa1/0x530
[ 53.982634][ C1] net_rx_action+0x567/0x1270
[ 53.982634][ C1] __do_softirq+0x28a/0x9ba
[ 53.982634][ C1] run_ksoftirqd+0x32/0x60
[ 53.982634][ C1] smpboot_thread_fn+0x559/0x8c0
[ 53.982634][ C1] kthread+0x3b9/0x490
[ 53.982634][ C1] ret_from_fork+0x22/0x30
[ 53.982634][ C1] </TASK>

Address the issue by skipping the GRO stage for shared or cloned skbs.
To reduce the chance of OoO, try to unclone the skbs before giving up.

v1 -> v2:
- use avoid skb_copy and fallback to netif_receive_skb - Eric

En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: veth: asegúrese de que los skb que ingresan a GRO no estén clonados. Después de confirmar d3256efd8e8b ("veth: permitir habilitar NAPI incluso sin XDP"), si GRO está habilitado en un dispositivo veth y TSO está deshabilitado en el dispositivo par, los skbs TCP pasarán por la devolución de llamada de NAPI. Si no hay ningún programa XDP adjunto, el código veth no realiza ninguna verificación compartida y los skbs compartidos/clonados podrían ingresar al motor GRO. Ignat informó de un ERROR que se activó más tarde debido a la condición anterior: [53.970529][C1] ERROR del kernel en net/core/skbuff.c:3574. [ 53.981755][ C1] código de operación no válido: 0000 [#1] PREEMPT SMP KASAN PTI [ 53.982634][ C1] CPU: 1 PID: 19 Comm: ksoftirqd/1 No contaminado 5.16.0-rc5+ #25 [ 53.982634][ C1] Nombre del hardware: PC estándar QEMU (Q35 + ICH9, 2009), BIOS 0.0.0 06/02/2015 [ 53.982634][ C1] RIP: 0010:skb_shift+0x13ef/0x23b0 [ 53.982634][ C1] Código: ea 03 0f b6 04 02 48 89 fa 83 e2 07 38 d0 7f 08 84 c0 0f 85 41 0c 00 00 41 80 7f 02 00 4d 8d b5 d0 00 00 00 0f 85 74 f5 ff ff &lt;0f&gt; 0b 4d 8d 77 20 be 04 00 00 00 4c 89 44 24 78 4c 89 f7 4c 89 8c [ 53.982634][ C1] RSP: 0018:ffff8881008f7008 EFLAGS: 00010246 [ 53.982634][ C1] RAX: 0000000000000000000000 RB X: ffff8881180b4c80 RCX: 0000000000000000 [ 53.982634][ C1] RDX: 00000000000000002 RSI: ffff8881180b4d3c RDI: ffff88810bc9cac2 [ 53.982634][ C1] RBP: ffff8881008f70b8 R08: ffff8881180b4cf4 R09: ffff8881180b4cf0 [ 53.982634][ C1] R10: ff ffed1022999e5c R11: 0000000000000002 R12: 0000000000000590 [ 53.982634][ C1] R13: ffff88810f940c80 R14: ffff88810f940d50 R15: ffff88810bc9cac0 [ 53.982634][ C1] FS: 00000000000000000(0000) GS:ffff888235880000(0000) knlGS:00000000000000000 [ 53.982634][ C1] CS: 0010 DS: 00 00 ES: 0000 CR0: 0000000080050033 [ 53.982634][ C1] CR2: 00007ff5f9b86680 CR3 : 0000000108ce8004 CR4: 0000000000170ee0 [ 53.982634][ C1] Seguimiento de llamadas: [ 53.982634][ C1] [ 53.982634][ C1] tcp_sacktag_walk+0xaba/0x18e0 [ 53.982634][ C1] t cp_sacktag_write_queue+0xe7b/0x3460 [ 53.982634][ C1 ] tcp_ack+0x2666/0x54b0 [ 53.982634][ C1] tcp_rcv_establecido+0x4d9/0x20f0 [ 53.982634][ C1] tcp_v4_do_rcv+0x551/0x810 [ 53.982634][ C1] tcp_v4_rcv+0x 22ed/0x2ed0 [ 53.982634][ C1] ip_protocol_deliver_rcu+0x96/0xaf0 [ 53.982634][ C1] ip_local_deliver_finish+0x1e0/0x2f0 [ 53.982634][ C1] ip_sublist_rcv_finish+0x211/0x440 [ 53.982634][ C1] ip_list_rcv_finish.constprop.0+0x424/0x660 [ 53.9 82634][C1] ip_list_rcv+0x2c8/0x410 [ 53.982634 ][ C1] __netif_receive_skb_list_core+0x65c/0x910 [ 53.982634][ C1] netif_receive_skb_list_internal+0x5f9/0xcb0 [ 53.982634][ C1] napi_complete_done+0x188/0x6e0 [ 53.982634][ C1] gro_cell_ encuesta+0x10c/0x1d0 [ 53.982634][ C1] __napi_poll+ 0xa1/0x530 [ 53.982634][ C1] net_rx_action+0x567/0x1270 [ 53.982634][ C1] __do_softirq+0x28a/0x9ba [ 53.982634][ C1] run_ksoftirqd+0x32/0x60 [ 53.982634][ C1] smpboot_thread_fn+0x559/0x8c0 [53.982634] [ C1] kthread+0x3b9/0x490 [ 53.982634][ C1] ret_from_fork+0x22/0x30 [ 53.982634][ C1] Solucione el problema omitiendo la etapa GRO para skbs compartidos o clonados. Para reducir la posibilidad de OoO, intente desbloquear los skbs antes de darse por vencido. v1 -&gt; v2: - use evitar skb_copy y recurra a netif_receive_skb - Eric

*Credits: N/A
CVSS Scores
Attack Vector
Local
Attack Complexity
Low
Privileges Required
High
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High
* Common Vulnerability Scoring System
SSVC
  • Decision:Track
Exploitation
None
Automatable
No
Tech. Impact
Partial
* Organization's Worst-case Scenario
Timeline
  • 2024-02-29 CVE Reserved
  • 2024-03-04 CVE Published
  • 2024-03-05 EPSS Updated
  • 2024-08-04 CVE Updated
  • ---------- Exploited in Wild
  • ---------- KEV Due Date
  • ---------- First Exploit
CWE
  • CWE-20: Improper Input Validation
CAPEC
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"
 >= 5.13 < 5.15.12
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.13 < 5.15.12"
en
Affected
Linux
Search vendor "Linux"
 Linux Kernel
Search vendor "Linux" for product "Linux Kernel"
 >= 5.13 < 5.16
Search vendor "Linux" for product "Linux Kernel" and version " >= 5.13 < 5.16"
en
Affected