CVE-2022-49814 (GCVE-0-2022-49814)
Vulnerability from cvelistv5
Published
2025-05-01 14:09
Modified
2026-08-05 08:56
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: kcm: close race conditions on sk_receive_queue sk->sk_receive_queue is protected by skb queue lock, but for KCM sockets its RX path takes mux->rx_lock to protect more than just skb queue. However, kcm_recvmsg() still only grabs the skb queue lock, so race conditions still exist. We can teach kcm_recvmsg() to grab mux->rx_lock too but this would introduce a potential performance regression as struct kcm_mux can be shared by multiple KCM sockets. So we have to enforce skb queue lock in requeue_rx_msgs() and handle skb peek case carefully in kcm_wait_data(). Fortunately, skb_recv_datagram() already handles it nicely and is widely used by other sockets, we can just switch to skb_recv_datagram() after getting rid of the unnecessary sock lock in kcm_recvmsg() and kcm_splice_read(). Side note: SOCK_DONE is not used by KCM sockets, so it is safe to get rid of this check too. I ran the original syzbot reproducer for 30 min without seeing any issue.
References
Impacted products
Vendor Product Version
Linux Linux Version: ab7ac4eb9832e32a09f4e8042705484d2fb0aad3
Version: ab7ac4eb9832e32a09f4e8042705484d2fb0aad3
Version: ab7ac4eb9832e32a09f4e8042705484d2fb0aad3
Version: ab7ac4eb9832e32a09f4e8042705484d2fb0aad3
Version: ab7ac4eb9832e32a09f4e8042705484d2fb0aad3
Version: ab7ac4eb9832e32a09f4e8042705484d2fb0aad3
Version: ab7ac4eb9832e32a09f4e8042705484d2fb0aad3
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/kcm/kcmsock.c"
          ],
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          "vendor": "Linux",
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        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
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          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "version": "0",
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              "version": "4.19.267",
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            },
            {
              "lessThanOrEqual": "5.4.*",
              "status": "unaffected",
              "version": "5.4.225",
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            },
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              "status": "unaffected",
              "version": "5.10.156",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.80",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.0.*",
              "status": "unaffected",
              "version": "6.0.10",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "4.14.300",
                  "versionStartIncluding": "4.6",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "4.19.267",
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                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nkcm: close race conditions on sk_receive_queue\n\nsk-\u003esk_receive_queue is protected by skb queue lock, but for KCM\nsockets its RX path takes mux-\u003erx_lock to protect more than just\nskb queue. However, kcm_recvmsg() still only grabs the skb queue\nlock, so race conditions still exist.\n\nWe can teach kcm_recvmsg() to grab mux-\u003erx_lock too but this would\nintroduce a potential performance regression as struct kcm_mux can\nbe shared by multiple KCM sockets.\n\nSo we have to enforce skb queue lock in requeue_rx_msgs() and handle\nskb peek case carefully in kcm_wait_data(). Fortunately,\nskb_recv_datagram() already handles it nicely and is widely used by\nother sockets, we can just switch to skb_recv_datagram() after\ngetting rid of the unnecessary sock lock in kcm_recvmsg() and\nkcm_splice_read(). Side note: SOCK_DONE is not used by KCM sockets,\nso it is safe to get rid of this check too.\n\nI ran the original syzbot reproducer for 30 min without seeing any\nissue."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The race is triggered only via local AF_KCM syscalls (socket, SIOCKCMATTACH/CLONE, setsockopt KCM_RECV_DISABLE/close, and recvmsg/recvmmsg); remote TCP data may fill the queue but cannot alone exercise the unlocked requeue versus recvmsg window.\nAC:L - The attacker controls both sides of the race\u2014one thread in kcm_recvmsg while another drives requeue_rx_msgs via KCM_RECV_DISABLE, close/kcm_done, or mux RX paths on sockets they created\u2014and can retry indefinitely; syzbot reproduced a GPF in skb_unlink with a C repro.\nPR:L - net/kcm/ has no capable()/CAP_NET_ADMIN checks; AF_KCM autoloads via MODULE_ALIAS_NETPROTO(PF_KCM), and an unprivileged user can create KCM sockets, attach their own TCP socket with a SOCKET_FILTER, and trigger the race (same PR:L posture as CVE-2025-38717).\nUI:N - The attacker performs socket setup, attach/clone, concurrent recvmsg and disable/close entirely themselves; no victim action is required.\nS:U - This is a standard in-kernel sk_buff heap use-after-free within the host kernel authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - The race leaves recvmsg holding a pointer to an sk_buff already dequeued/freed by requeue_rx_msgs, a reclaimable heap UAF that enables arbitrary kernel read via spray/reuse of the freed skb.\nI:H - Concurrent unlocked unlink/dequeue corrupts the receive-queue list and can double-free the skb, giving a heap write/control-flow primitive consistent with treating exploitable kernel UAFs as High integrity.\nA:H - Even without full exploitation, the bug causes a general protection fault/oops in skb_unlink from kcm_recvmsg (as demonstrated by syzbot), which is a full kernel availability impact."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T08:56:23.170Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/22f6b5d47396b4287662668ee3f5c1f766cb4259"
        },
        {
          "url": "https://git.kernel.org/stable/c/d9ad4de92e184b19bcae4da10dac0275abf83931"
        },
        {
          "url": "https://git.kernel.org/stable/c/ce57d6474ae999a3b2d442314087473a646a65c7"
        },
        {
          "url": "https://git.kernel.org/stable/c/4154b6afa2bd639214ff259d912faad984f7413a"
        },
        {
          "url": "https://git.kernel.org/stable/c/f7b0e95071bb4be4b811af3f0bfc3e200eedeaa3"
        },
        {
          "url": "https://git.kernel.org/stable/c/bf92e54597d842da127c59833b365d6faeeaf020"
        },
        {
          "url": "https://git.kernel.org/stable/c/5121197ecc5db58c07da95eb1ff82b98b121a221"
        }
      ],
      "title": "kcm: close race conditions on sk_receive_queue",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2022-49814",
    "datePublished": "2025-05-01T14:09:38.389Z",
    "dateReserved": "2025-05-01T14:05:17.226Z",
    "dateUpdated": "2026-08-05T08:56:23.170Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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