fkie_cve-2021-47546
Vulnerability from fkie_nvd
Published
2024-05-24 15:15
Modified
2024-11-21 06:36
Severity ?
5.5 (Medium) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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_kernel *
linux linux_kernel *
linux linux_kernel *


To clipboard 

{
   configurations: [
      {
         nodes: [
            {
               cpeMatch: [
                  {
                     criteria: "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                     matchCriteriaId: "1C6E0E5A-819B-4CEA-BD4B-6647308627E7",
                     versionEndExcluding: "5.4.164",
                     versionStartIncluding: "5.4",
                     vulnerable: true,
                  },
                  {
                     criteria: "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                     matchCriteriaId: "AE5B4333-2C46-40C3-8B42-0168AD91DDE1",
                     versionEndExcluding: "5.10.84",
                     versionStartIncluding: "5.5",
                     vulnerable: true,
                  },
                  {
                     criteria: "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                     matchCriteriaId: "A696A60B-2782-4119-83DD-1EFFBC903F02",
                     versionEndExcluding: "5.15.7",
                     versionStartIncluding: "5.11",
                     vulnerable: true,
                  },
               ],
               negate: false,
               operator: "OR",
            },
         ],
      },
   ],
   cveTags: [],
   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->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. [1]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038c3266e26/net/ipv6/fib6_rules.c#L71 [2]: https://github.com/torvalds/linux/blob/ca7a03c4175366a92cee0ccc4fec0038 c3266e26/net /ipv6/fib6_rules.c#L99",
      },
   ],
   id: "CVE-2021-47546",
   lastModified: "2024-11-21T06:36:30.640",
   metrics: {
      cvssMetricV31: [
         {
            cvssData: {
               attackComplexity: "LOW",
               attackVector: "LOCAL",
               availabilityImpact: "HIGH",
               baseScore: 5.5,
               baseSeverity: "MEDIUM",
               confidentialityImpact: "NONE",
               integrityImpact: "NONE",
               privilegesRequired: "LOW",
               scope: "UNCHANGED",
               userInteraction: "NONE",
               vectorString: "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
               version: "3.1",
            },
            exploitabilityScore: 1.8,
            impactScore: 3.6,
            source: "nvd@nist.gov",
            type: "Primary",
         },
      ],
   },
   published: "2024-05-24T15:15:19.450",
   references: [
      {
         source: "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
         tags: [
            "Patch",
         ],
         url: "https://git.kernel.org/stable/c/209d35ee34e25f9668c404350a1c86d914c54ffa",
      },
      {
         source: "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
         tags: [
            "Patch",
         ],
         url: "https://git.kernel.org/stable/c/8ef8a76a340ebdb2c2eea3f6fb0ebbed09a16383",
      },
      {
         source: "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
         tags: [
            "Patch",
         ],
         url: "https://git.kernel.org/stable/c/cdef485217d30382f3bf6448c54b4401648fe3f1",
      },
      {
         source: "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
         tags: [
            "Patch",
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         url: "https://git.kernel.org/stable/c/ee38eb8cf9a7323884c2b8e0adbbeb2192d31e29",
      },
      {
         source: "af854a3a-2127-422b-91ae-364da2661108",
         tags: [
            "Patch",
         ],
         url: "https://git.kernel.org/stable/c/209d35ee34e25f9668c404350a1c86d914c54ffa",
      },
      {
         source: "af854a3a-2127-422b-91ae-364da2661108",
         tags: [
            "Patch",
         ],
         url: "https://git.kernel.org/stable/c/8ef8a76a340ebdb2c2eea3f6fb0ebbed09a16383",
      },
      {
         source: "af854a3a-2127-422b-91ae-364da2661108",
         tags: [
            "Patch",
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         url: "https://git.kernel.org/stable/c/cdef485217d30382f3bf6448c54b4401648fe3f1",
      },
      {
         source: "af854a3a-2127-422b-91ae-364da2661108",
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         url: "https://git.kernel.org/stable/c/ee38eb8cf9a7323884c2b8e0adbbeb2192d31e29",
      },
   ],
   sourceIdentifier: "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
   vulnStatus: "Modified",
   weaknesses: [
      {
         description: [
            {
               lang: "en",
               value: "CWE-401",
            },
         ],
         source: "nvd@nist.gov",
         type: "Primary",
      },
   ],
}


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