cve-2021-47546
Vulnerability from cvelistv5
Published
2024-05-24 15:09
Modified
2024-11-04 12:07
Severity ?
EPSS score ?
Summary
ipv6: fix memory leak in fib6_rule_suppress
References
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"include/net/fib_rules.h",
"net/core/fib_rules.c",
"net/ipv4/fib_rules.c",
"net/ipv6/fib6_rules.c"
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: fix memory leak in fib6_rule_suppress\n\nThe kernel leaks memory when a `fib` rule is present in IPv6 nftables\nfirewall rules and a suppress_prefix rule is present in the IPv6 routing\nrules (used by certain tools such as wg-quick). 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-\u003eflags` 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 \u0027{ type filter hook prerouting priority filter + 10; policy accept; }\u0027\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"
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"nvd": "{\"cve\":{\"id\":\"CVE-2021-47546\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2024-05-24T15:15:19.450\",\"lastModified\":\"2024-06-10T18:30:20.320\",\"vulnStatus\":\"Analyzed\",\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nipv6: fix memory leak in fib6_rule_suppress\\n\\nThe kernel leaks memory when a `fib` rule is present in IPv6 nftables\\nfirewall rules and a suppress_prefix rule is present in the IPv6 routing\\nrules (used by certain tools such as wg-quick). 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-\u003eflags` 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 \u0027{ type filter hook prerouting priority filter + 10; policy accept; }\u0027\\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 resolvi\u00f3 la siguiente vulnerabilidad: ipv6: corrige la p\u00e9rdida de memoria en fib6_rule_suppress El kernel pierde memoria cuando una regla `fib` est\u00e1 presente en las reglas de firewall de nftables de IPv6 y una regla de supresi\u00f3n_prefix est\u00e1 presente en las reglas de enrutamiento de IPv6 (utilizadas por ciertas herramientas como wg-quick). En tales escenarios, cada paquete entrante perder\u00e1 una asignaci\u00f3n en el cach\u00e9 de losa `ip6_dst_cache`. Despu\u00e9s de algunas horas de `bpftrace`-ing y lectura del c\u00f3digo fuente, rastre\u00e9 el problema hasta ca7a03c41753 (\\\"ipv6: no libere rt si FIB_LOOKUP_NOREF est\u00e1 configurado en la regla de supresi\u00f3n\\\"). El problema con ese cambio es que los `args-\u0026gt;flags` gen\u00e9ricos siempre tienen `FIB_LOOKUP_NOREF` configurado[1][2] pero el indicador espec\u00edfico de IPv6 `RT6_LOOKUP_F_DST_NOREF` podr\u00eda no estarlo, lo que lleva a que `fib6_rule_suppress` no disminuya el recuento cuando necesario. C\u00f3mo 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 \u0027{ tipo filtro gancho prerouting filtro de prioridad + 10; aceptar pol\u00edtica; }\u0027 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 espec\u00edficos del protocolo a la funci\u00f3n `suprimir` espec\u00edfica del protocolo y verifica el argumento `flags` espec\u00edfico del protocolo para RT6_LOOKUP_F_DST_NOREF en lugar del FIB_LOOKUP_NOREF gen\u00e9rico al disminuir el recuento, de esta manera. 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- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.