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l2tp: prevent possible tunnel refcount underflow

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: l2tp: prevent possible tunnel refcount underflow When a session is created, it sets a backpointer to its tunnel. When the session refcount drops to 0, l2tp_session_free drops the tunnel refcount if session->tunnel is non-NULL. However, session->tunnel is set in l2tp_session_create, before the tunnel refcount is incremented by l2tp_session_register, which leaves a small window where session->tunnel is non-NULL when the tunnel refcount hasn't been bumped. Moving the assignment to l2tp_session_register is trivial but l2tp_session_create calls l2tp_session_set_header_len which uses session->tunnel to get the tunnel's encap. Add an encap arg to l2tp_session_set_header_len to avoid using session->tunnel. If l2tpv3 sessions have colliding IDs, it is possible for l2tp_v3_session_get to race with l2tp_session_register and fetch a session which doesn't yet have session->tunnel set. Add a check for this case.

Announced Source revision 1
Original source ↗

CVE-2024-49940

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2024-49940

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "3953ae7b218df4d1e544b98a393666f9ae58a78c",
        "lessThan": "98691b2e28a6c3dac0680914493d54c77f215755",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "3953ae7b218df4d1e544b98a393666f9ae58a78c",
        "lessThan": "f7415e60c25a6108cd7955a20b2e66b6251ffe02",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "3953ae7b218df4d1e544b98a393666f9ae58a78c",
        "lessThan": "24256415d18695b46da06c93135f5b51c548b950",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "b102bfc2a90d14f342580285782a9a51c74f7369",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "10c15ddabbcf888922adbdd44ca3fecf6eab19d9",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "8d1c650d452c53fcb3f02a7b1d772741639f89a4",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "12b5fb58ac993c24210cf8cbc72d407d3a4e6490",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "aef37401b467a0b1a9517c69924a1d66937e0789",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "3.2.99",
        "lessThan": "3.3",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "3.16.54",
        "lessThan": "3.17",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "4.4.225",
        "lessThan": "4.5",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "4.9.225",
        "lessThan": "4.10",
        "versionType": "semver"
      },
      {
        "status": "affected",
        "version": "4.14.182",
        "lessThan": "4.15",
        "versionType": "semver"
      }
    ],
    "programFiles": [
      "net/l2tp/l2tp_core.c",
      "net/l2tp/l2tp_core.h",
      "net/l2tp/l2tp_netlink.c",
      "net/l2tp/l2tp_ppp.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "4.15"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "4.15",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "6.6.160",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.11.3",
        "versionType": "semver",
        "lessThanOrEqual": "6.11.*"
      },
      {
        "status": "unaffected",
        "version": "6.12",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "net/l2tp/l2tp_core.c",
      "net/l2tp/l2tp_core.h",
      "net/l2tp/l2tp_netlink.c",
      "net/l2tp/l2tp_ppp.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2024-49940

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#45912 · Revision 1
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Publisher date
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