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-\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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      "containers": "{\"adp\": [{\"title\": \"CVE Program Container\", \"references\": [{\"url\": \"https://git.kernel.org/stable/c/ee38eb8cf9a7323884c2b8e0adbbeb2192d31e29\", \"tags\": [\"x_transferred\"]}, {\"url\": \"https://git.kernel.org/stable/c/209d35ee34e25f9668c404350a1c86d914c54ffa\", \"tags\": [\"x_transferred\"]}, {\"url\": \"https://git.kernel.org/stable/c/8ef8a76a340ebdb2c2eea3f6fb0ebbed09a16383\", \"tags\": [\"x_transferred\"]}, {\"url\": \"https://git.kernel.org/stable/c/cdef485217d30382f3bf6448c54b4401648fe3f1\", \"tags\": [\"x_transferred\"]}], \"providerMetadata\": {\"orgId\": \"af854a3a-2127-422b-91ae-364da2661108\", \"shortName\": \"CVE\", \"dateUpdated\": \"2024-08-04T05:39:59.755Z\"}}, {\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2021-47546\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2024-06-17T17:34:31.593424Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2024-06-17T17:34:32.582Z\"}}], \"cna\": {\"title\": \"ipv6: fix memory leak in fib6_rule_suppress\", \"affected\": [{\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"ca7a03c4175366a92cee0ccc4fec0038c3266e26\", \"lessThan\": \"ee38eb8cf9a7323884c2b8e0adbbeb2192d31e29\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"ca7a03c4175366a92cee0ccc4fec0038c3266e26\", \"lessThan\": \"209d35ee34e25f9668c404350a1c86d914c54ffa\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"ca7a03c4175366a92cee0ccc4fec0038c3266e26\", \"lessThan\": \"8ef8a76a340ebdb2c2eea3f6fb0ebbed09a16383\", \"versionType\": \"git\"}, {\"status\": \"affected\", \"version\": \"ca7a03c4175366a92cee0ccc4fec0038c3266e26\", \"lessThan\": \"cdef485217d30382f3bf6448c54b4401648fe3f1\", \"versionType\": \"git\"}], \"programFiles\": [\"include/net/fib_rules.h\", \"net/core/fib_rules.c\", \"net/ipv4/fib_rules.c\", \"net/ipv6/fib6_rules.c\"], \"defaultStatus\": \"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"5.4\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"5.4\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"5.4.164\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.4.*\"}, {\"status\": \"unaffected\", \"version\": \"5.10.84\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.15.7\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.15.*\"}, {\"status\": \"unaffected\", \"version\": \"5.16\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"include/net/fib_rules.h\", \"net/core/fib_rules.c\", \"net/ipv4/fib_rules.c\", \"net/ipv6/fib6_rules.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/ee38eb8cf9a7323884c2b8e0adbbeb2192d31e29\"}, {\"url\": \"https://git.kernel.org/stable/c/209d35ee34e25f9668c404350a1c86d914c54ffa\"}, {\"url\": \"https://git.kernel.org/stable/c/8ef8a76a340ebdb2c2eea3f6fb0ebbed09a16383\"}, {\"url\": \"https://git.kernel.org/stable/c/cdef485217d30382f3bf6448c54b4401648fe3f1\"}], \"x_generator\": {\"engine\": \"bippy-5f407fcff5a0\"}, \"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\"}], \"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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