{
  "schema_version": "1.6.1",
  "id": "RPI-CVE-2026-43050",
  "modified": "2026-10-07T17:22:01Z",
  "upstream": [
    "CVE-2026-43050"
  ],
  "published": "2026-05-01T14:17:31Z",
  "summary": "atm: lec: fix use-after-free in sock_def_readable()",
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\natm: lec: fix use-after-free in sock_def_readable()\n\nA race condition exists between lec_atm_close() setting priv->lecd\nto NULL and concurrent access to priv->lecd in send_to_lecd(),\nlec_handle_bridge(), and lec_atm_send(). When the socket is freed\nvia RCU while another thread is still using it, a use-after-free\noccurs in sock_def_readable() when accessing the socket's wait queue.\n\nThe root cause is that lec_atm_close() clears priv->lecd without\nany synchronization, while callers dereference priv->lecd without\nany protection against concurrent teardown.\n\nFix this by converting priv->lecd to an RCU-protected pointer:\n- Mark priv->lecd as __rcu in lec.h\n- Use rcu_assign_pointer() in lec_atm_close() and lecd_attach()\n  for safe pointer assignment\n- Use rcu_access_pointer() for NULL checks that do not dereference\n  the pointer in lec_start_xmit(), lec_push(), send_to_lecd() and\n  lecd_attach()\n- Use rcu_read_lock/rcu_dereference/rcu_read_unlock in send_to_lecd(),\n  lec_handle_bridge() and lec_atm_send() to safely access lecd\n- Use rcu_assign_pointer() followed by synchronize_rcu() in\n  lec_atm_close() to ensure all readers have completed before\n  proceeding. This is safe since lec_atm_close() is called from\n  vcc_release() which holds lock_sock(), a sleeping lock.\n- Remove the manual sk_receive_queue drain from lec_atm_close()\n  since vcc_destroy_socket() already drains it after lec_atm_close()\n  returns.\n\nv2: Switch from spinlock + sock_hold/put approach to RCU to properly\n    fix the race. The v1 spinlock approach had two issues pointed out\n    by Eric Dumazet:\n    1. priv->lecd was still accessed directly after releasing the\n       lock instead of using a local copy.\n    2. The spinlock did not prevent packets being queued after\n       lec_atm_close() drains sk_receive_queue since timer and\n       workqueue paths bypass netif_stop_queue().\n\nNote: Syzbot patch testing was attempted but the test VM terminated\n    unexpectedly with \"Connection to localhost closed by remote host\",\n    likely due to a QEMU AHCI emulation issue unrelated to this fix.\n    Compile testing with \"make W=1 net/atm/lec.o\" passes cleanly.",
  "affected": [
    {
      "package": {
        "ecosystem": "Raspberry Pi OS:12",
        "name": "linux"
      },
      "versions": [
        "1:6.1.47-1+rpt4"
      ],
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-2712",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v6",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v7l",
            "binary_version": "1:6.1.47-1+rpt4"
          },
          {
            "binary_name": "linux-image-6.1.0-rpi3-rpi-v8",
            "binary_version": "1:6.1.47-1+rpt4"
          }
        ]
      },
      "database_specific": {
        "per_version": {
          "1:6.1.47-1+rpt4": {
            "linux_commit": "655fc658a15ae7a6f37103754adb39ba52a9a14e",
            "upstream_version": "6.1.47",
            "assessment": "commit ancestry (strak rule)",
            "upstream_fixed": "6.1.168",
            "compiled_filter": false
          }
        }
      }
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.cve.org/CVERecord?id=CVE-2026-43050"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/3e8b25f32f2f35549d03d77da030a24a45bdef5b"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/750a33f417f3d196b86375f8d9f8938bacf130fe"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/317843d5355062020649124eb4a0d7acbcc3f53e"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/b256d055da47258e63f8b40965f276c5f23d229a"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/3989740fa4978e1d2d51ecc62be1b01093e104ad"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/abc10f85a3965ac14b9ed7ad3e67b35604a63aa3"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/5fbbb1ff936d7ff9528d929c1549977e8123d8a8"
    },
    {
      "type": "FIX",
      "url": "https://git.kernel.org/stable/c/922814879542c2e397b0e9641fd36b8202a8e555"
    }
  ],
  "database_specific": {
    "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git",
    "upstream_modified": "2026-05-12T04:54:46Z"
  }
}