cve-2021-47546
Vulnerability from cvelistv5
Published
2024-05-24 15:09
Modified
2024-12-19 07:44
Severity ?
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: fix memory leak in fib6_rule_suppress The kernel leaks memory when a `fib` rule is present in IPv6 nftables firewall rules and a suppress_prefix rule is present in the IPv6 routing rules (used by certain tools such as wg-quick). In such scenarios, every incoming packet will leak an allocation in `ip6_dst_cache` slab cache. After some hours of `bpftrace`-ing and source code reading, I tracked down the issue to ca7a03c41753 ("ipv6: do not free rt if FIB_LOOKUP_NOREF is set on suppress rule"). The problem with that change is that the generic `args->flags` always have `FIB_LOOKUP_NOREF` set[1][2] but the IPv6-specific flag `RT6_LOOKUP_F_DST_NOREF` might not be, leading to `fib6_rule_suppress` not decreasing the refcount when needed. How to reproduce: - Add the following nftables rule to a prerouting chain: meta nfproto ipv6 fib saddr . mark . iif oif missing drop This can be done with: sudo nft create table inet test sudo nft create chain inet test test_chain '{ type filter hook prerouting priority filter + 10; policy accept; }' sudo nft add rule inet test test_chain meta nfproto ipv6 fib saddr . mark . iif oif missing drop - Run: sudo ip -6 rule add table main suppress_prefixlength 0 - Watch `sudo slabtop -o | grep ip6_dst_cache` to see memory usage increase with every incoming ipv6 packet. This patch exposes the protocol-specific flags to the protocol specific `suppress` function, and check the protocol-specific `flags` argument for RT6_LOOKUP_F_DST_NOREF instead of the generic FIB_LOOKUP_NOREF when decreasing the refcount, like this. [1]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L71 [2]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L99
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/209d35ee34e25f9668c404350a1c86d914c54ffaPatch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/8ef8a76a340ebdb2c2eea3f6fb0ebbed09a16383Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/cdef485217d30382f3bf6448c54b4401648fe3f1Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/ee38eb8cf9a7323884c2b8e0adbbeb2192d31e29Patch
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/209d35ee34e25f9668c404350a1c86d914c54ffaPatch
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/8ef8a76a340ebdb2c2eea3f6fb0ebbed09a16383Patch
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/cdef485217d30382f3bf6448c54b4401648fe3f1Patch
af854a3a-2127-422b-91ae-364da2661108https://git.kernel.org/stable/c/ee38eb8cf9a7323884c2b8e0adbbeb2192d31e29Patch
Impacted products
Vendor Product Version
Linux Linux Version: ca7a03c4175366a92cee0ccc4fec0038c3266e26
Version: ca7a03c4175366a92cee0ccc4fec0038c3266e26
Version: ca7a03c4175366a92cee0ccc4fec0038c3266e26
Version: ca7a03c4175366a92cee0ccc4fec0038c3266e26
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   Linux Linux Version: 5.4
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In such scenarios, every\\nincoming packet will leak an allocation in `ip6_dst_cache` slab cache.\\n\\nAfter some hours of `bpftrace`-ing and source code reading, I tracked\\ndown the issue to ca7a03c41753 (\\\"ipv6: do not free rt if\\nFIB_LOOKUP_NOREF is set on suppress rule\\\").\\n\\nThe problem with that change is that the generic `args->flags` always have\\n`FIB_LOOKUP_NOREF` set[1][2] but the IPv6-specific flag\\n`RT6_LOOKUP_F_DST_NOREF` might not be, leading to `fib6_rule_suppress` not\\ndecreasing the refcount when needed.\\n\\nHow to reproduce:\\n - Add the following nftables rule to a prerouting chain:\\n     meta nfproto ipv6 fib saddr . mark . iif oif missing drop\\n   This can be done with:\\n     sudo nft create table inet test\\n     sudo nft create chain inet test test_chain '{ type filter hook prerouting priority filter + 10; policy accept; }'\\n     sudo nft add rule inet test test_chain meta nfproto ipv6 fib saddr . mark . iif oif missing drop\\n - Run:\\n     sudo ip -6 rule add table main suppress_prefixlength 0\\n - Watch `sudo slabtop -o | grep ip6_dst_cache` to see memory usage increase\\n   with every incoming ipv6 packet.\\n\\nThis patch exposes the protocol-specific flags to the protocol\\nspecific `suppress` function, and check the protocol-specific `flags`\\nargument for RT6_LOOKUP_F_DST_NOREF instead of the generic\\nFIB_LOOKUP_NOREF when decreasing the refcount, like this.\\n\\n[1]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L71\\n[2]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L99\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se resolvió la siguiente vulnerabilidad: ipv6: corrige la pérdida de memoria en fib6_rule_suppress El kernel pierde memoria cuando una regla `fib` está presente en las reglas de firewall de nftables de IPv6 y una regla de supresión_prefix está presente en las reglas de enrutamiento de IPv6 (utilizadas por ciertas herramientas como wg-quick). En tales escenarios, cada paquete entrante perderá una asignación en el caché de losa `ip6_dst_cache`. Después de algunas horas de `bpftrace`-ing y lectura del código fuente, rastreé el problema hasta ca7a03c41753 (\\\"ipv6: no libere rt si FIB_LOOKUP_NOREF está configurado en la regla de supresión\\\"). El problema con ese cambio es que los `args->flags` genéricos siempre tienen `FIB_LOOKUP_NOREF` configurado[1][2] pero el indicador específico de IPv6 `RT6_LOOKUP_F_DST_NOREF` podría no estarlo, lo que lleva a que `fib6_rule_suppress` no disminuya el recuento cuando necesario. Cómo reproducir: - Agregue la siguiente regla nftables a una cadena de enrutamiento previo: meta nfproto ipv6 fib saddr. marca . iif oif falta gota Esto se puede hacer con: sudo nft create table inet test sudo nft create chain inet test test_chain '{ tipo filtro gancho prerouting filtro de prioridad + 10; aceptar política; }' sudo nft agregar regla inet test test_chain meta nfproto ipv6 fib saddr. marca . iif oif falta gota - Ejecutar: sudo ip -6 regla agregar tabla principal suprimir_prefixlength 0 - Ver `sudo slabtop -o | grep ip6_dst_cache` para ver el aumento del uso de memoria con cada paquete ipv6 entrante. Este parche expone los indicadores específicos del protocolo a la función `suprimir` específica del protocolo y verifica el argumento `flags` específico del protocolo para RT6_LOOKUP_F_DST_NOREF en lugar del FIB_LOOKUP_NOREF genérico al disminuir el recuento, de esta manera. 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In such scenarios, every\\nincoming packet will leak an allocation in `ip6_dst_cache` slab cache.\\n\\nAfter some hours of `bpftrace`-ing and source code reading, I tracked\\ndown the issue to ca7a03c41753 (\\\"ipv6: do not free rt if\\nFIB_LOOKUP_NOREF is set on suppress rule\\\").\\n\\nThe problem with that change is that the generic `args->flags` always have\\n`FIB_LOOKUP_NOREF` set[1][2] but the IPv6-specific flag\\n`RT6_LOOKUP_F_DST_NOREF` might not be, leading to `fib6_rule_suppress` not\\ndecreasing the refcount when needed.\\n\\nHow to reproduce:\\n - Add the following nftables rule to a prerouting chain:\\n     meta nfproto ipv6 fib saddr . mark . iif oif missing drop\\n   This can be done with:\\n     sudo nft create table inet test\\n     sudo nft create chain inet test test_chain '{ type filter hook prerouting priority filter + 10; policy accept; }'\\n     sudo nft add rule inet test test_chain meta nfproto ipv6 fib saddr . mark . iif oif missing drop\\n - Run:\\n     sudo ip -6 rule add table main suppress_prefixlength 0\\n - Watch `sudo slabtop -o | grep ip6_dst_cache` to see memory usage increase\\n   with every incoming ipv6 packet.\\n\\nThis patch exposes the protocol-specific flags to the protocol\\nspecific `suppress` function, and check the protocol-specific `flags`\\nargument for RT6_LOOKUP_F_DST_NOREF instead of the generic\\nFIB_LOOKUP_NOREF when decreasing the refcount, like this.\\n\\n[1]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L71\\n[2]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L99\"}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2024-12-19T07:44:32.919Z\"}}}",
         cveMetadata: "{\"cveId\": \"CVE-2021-47546\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2024-12-19T07:44:32.919Z\", \"dateReserved\": \"2024-05-24T15:02:54.829Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-05-24T15:09:51.286Z\", \"assignerShortName\": \"Linux\"}",
         dataType: "CVE_RECORD",
         dataVersion: "5.1",
      },
   },
}


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