GHSA-52C3-J5QJ-8HPP
Vulnerability from github – Published: 2026-07-19 18:31 – Updated: 2026-08-09 21:30In the Linux kernel, the following vulnerability has been resolved:
net/handshake: hand off the pinned file reference to accept_doit
handshake_req_next() removes the request from the per-net pending list and drops hn_lock before handshake_nl_accept_doit() reads req->hr_sk->sk_socket and dereferences sock->file (once in FD_PREPARE() and again in get_file()). In that window a consumer running tls_handshake_cancel() followed by sockfd_put() (svc_sock_free) or __fput_sync() (xs_reset_transport) releases sock->file. sock_release() then runs sock_orphan(), zeroing sk_socket, and frees the struct socket. The accept-side code either reads NULL through sk_socket or chases freed memory.
The submit-side sock_hold() does not prevent this. sk_refcnt protects struct sock, but struct socket and sock->file are independently refcounted via the file descriptor the consumer owns. Pinning sk leaves sock and sock->file unprotected.
Retarget the accept-side dereferences at req->hr_file, which was pinned at submit time, instead of req->hr_sk->sk_socket->file. Pinning on its own is not sufficient: a consumer that cancels between handshake_req_next() returning and accept_doit reaching FD_PREPARE() takes the !remove_pending() branch in handshake_req_cancel() and drops hr_file before the accept side takes its own reference. Hand off an additional file reference inside handshake_req_next(), under hn_lock, so the accept side operates on a reference that no concurrent handshake_req_cancel() can revoke. FD_PREPARE() consumes that handed-off reference, either by transferring it to the new fd in fd_publish() or by dropping it in the cleanup destructor on error; the explicit get_file() that previously balanced FD_PREPARE() is therefore redundant and goes away.
Update handshake_req_cancel_test2 and _test3 to simulate the FD_PREPARE() consumption with an fput() so the kunit file-count assertions stay balanced.
{
"affected": [],
"aliases": [
"CVE-2026-63979"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-07-19T16:17:17Z",
"severity": "CRITICAL"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/handshake: hand off the pinned file reference to accept_doit\n\nhandshake_req_next() removes the request from the per-net\npending list and drops hn_lock before handshake_nl_accept_doit()\nreads req-\u003ehr_sk-\u003esk_socket and dereferences sock-\u003efile (once in\nFD_PREPARE() and again in get_file()). In that window a\nconsumer running tls_handshake_cancel() followed by sockfd_put()\n(svc_sock_free) or __fput_sync() (xs_reset_transport) releases\nsock-\u003efile. sock_release() then runs sock_orphan(), zeroing\nsk_socket, and frees the struct socket. The accept-side code\neither reads NULL through sk_socket or chases freed memory.\n\nThe submit-side sock_hold() does not prevent this. sk_refcnt\nprotects struct sock, but struct socket and sock-\u003efile are\nindependently refcounted via the file descriptor the consumer\nowns. Pinning sk leaves sock and sock-\u003efile unprotected.\n\nRetarget the accept-side dereferences at req-\u003ehr_file, which was\npinned at submit time, instead of req-\u003ehr_sk-\u003esk_socket-\u003efile.\nPinning on its own is not sufficient: a consumer that cancels\nbetween handshake_req_next() returning and accept_doit reaching\nFD_PREPARE() takes the !remove_pending() branch in\nhandshake_req_cancel() and drops hr_file before the accept side\ntakes its own reference. Hand off an additional file reference\ninside handshake_req_next(), under hn_lock, so the accept side\noperates on a reference that no concurrent handshake_req_cancel()\ncan revoke. FD_PREPARE() consumes that handed-off reference,\neither by transferring it to the new fd in fd_publish() or by\ndropping it in the cleanup destructor on error; the explicit\nget_file() that previously balanced FD_PREPARE() is therefore\nredundant and goes away.\n\nUpdate handshake_req_cancel_test2 and _test3 to simulate the\nFD_PREPARE() consumption with an fput() so the kunit file-count\nassertions stay balanced.",
"id": "GHSA-52c3-j5qj-8hpp",
"modified": "2026-08-09T21:30:25Z",
"published": "2026-07-19T18:31:48Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63979"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/68eba6519cbd6359fb554a9720f3a3b6b2eba23f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c06876d4fac38f35820946ee3b1be7d7da799cd4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f4251190e58b209999c1ba9e6d2976136a1be055"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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