GHSA-WJV3-3R54-X298
Vulnerability from github – Published: 2026-07-27 21:31 – Updated: 2026-07-27 21:31In the Linux kernel, the following vulnerability has been resolved:
net/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket
smc_cdc_rx_handler() looks up the connection by token under the link group's conns_lock, drops the lock, and then dereferences conn and the smc_sock derived from it, ending in sock_hold(&smc->sk) inside smc_cdc_msg_recv(). No reference is held across the lock release.
The only reference pinning the socket while the connection is discoverable in the link group is taken in smc_lgr_register_conn() (sock_hold) and dropped in __smc_lgr_unregister_conn() (sock_put), both under conns_lock. Once the handler drops conns_lock, a concurrent close() -> smc_release() -> smc_conn_free() -> smc_lgr_unregister_conn() can drop that reference and free the smc_sock, so the handler's later sock_hold() runs on freed memory:
WARNING: lib/refcount.c:25 at refcount_warn_saturate Workqueue: rxe_wq do_work refcount_warn_saturate (lib/refcount.c:25) smc_cdc_msg_recv (net/smc/smc_cdc.c:430) smc_cdc_rx_handler (net/smc/smc_cdc.c:502) smc_wr_rx_tasklet_fn (net/smc/smc_wr.c:445) tasklet_action_common (kernel/softirq.c:938) handle_softirqs (kernel/softirq.c:622) Kernel panic - not syncing: panic_on_warn set
Only SMC-R is affected. The SMC-D receive tasklet is stopped by tasklet_kill(&conn->rx_tsklet) in smc_conn_free() before the connection is unregistered, so it cannot run concurrently with the free.
Take the socket reference while still holding conns_lock, so the registration reference can no longer be the last one, and drop it once the handler is done.
{
"affected": [],
"aliases": [
"CVE-2026-64541"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-07-27T21:17:06Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket\n\nsmc_cdc_rx_handler() looks up the connection by token under the link\ngroup\u0027s conns_lock, drops the lock, and then dereferences conn and the\nsmc_sock derived from it, ending in sock_hold(\u0026smc-\u003esk) inside\nsmc_cdc_msg_recv(). No reference is held across the lock release.\n\nThe only reference pinning the socket while the connection is\ndiscoverable in the link group is taken in smc_lgr_register_conn()\n(sock_hold) and dropped in __smc_lgr_unregister_conn() (sock_put), both\nunder conns_lock. Once the handler drops conns_lock, a concurrent\nclose() -\u003e smc_release() -\u003e smc_conn_free() -\u003e smc_lgr_unregister_conn()\ncan drop that reference and free the smc_sock, so the handler\u0027s later\nsock_hold() runs on freed memory:\n\n WARNING: lib/refcount.c:25 at refcount_warn_saturate\n Workqueue: rxe_wq do_work\n refcount_warn_saturate (lib/refcount.c:25)\n smc_cdc_msg_recv (net/smc/smc_cdc.c:430)\n smc_cdc_rx_handler (net/smc/smc_cdc.c:502)\n smc_wr_rx_tasklet_fn (net/smc/smc_wr.c:445)\n tasklet_action_common (kernel/softirq.c:938)\n handle_softirqs (kernel/softirq.c:622)\n Kernel panic - not syncing: panic_on_warn set\n\nOnly SMC-R is affected. The SMC-D receive tasklet is stopped by\ntasklet_kill(\u0026conn-\u003erx_tsklet) in smc_conn_free() before the connection\nis unregistered, so it cannot run concurrently with the free.\n\nTake the socket reference while still holding conns_lock, so the\nregistration reference can no longer be the last one, and drop it once\nthe handler is done.",
"id": "GHSA-wjv3-3r54-x298",
"modified": "2026-07-27T21:31:27Z",
"published": "2026-07-27T21:31:27Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-64541"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/1951bffbc6493ec34cff3956b29d4bc6606904a6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3bfb96d9bc6a7ed0b99c7db329cc2e22a28d84bb"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/472e9d7c0d5b03be3ff91ff941f57da822b031bc"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/647b19e5cc145a2f1f685ae8ff3805a17356888c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8145b432136285e01091815b48ceb2dae261f262"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8de4f665d0febfb92803dece377791a563fc7041"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/9d160b35cc34a2ba8229d07651468a7848325135"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ce5aa8084329351086894aa34d77e40301d5bd3d"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
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