GHSA-49C8-7MPF-M266
Vulnerability from github – Published: 2026-06-24 18:32 – Updated: 2026-06-28 09:31In the Linux kernel, the following vulnerability has been resolved:
net: qrtr: fix refcount saturation and potential UAF in qrtr_port_remove
In qrtr_port_remove(), the socket reference count is decremented via __sock_put() before the port is removed from the qrtr_ports XArray and before the RCU grace period elapses.
This breaks the fundamental RCU update paradigm. It exposes a race window where a concurrent RCU reader (such as qrtr_reset_ports() or qrtr_port_lookup()) can obtain a pointer to the socket from the XArray, and attempt to call sock_hold() on a socket whose reference count has already dropped to zero.
This exact race condition was hit during syzkaller fuzzing, leading to the following refcount saturation warning and a potential Use-After-Free:
refcount_t: saturated; leaking memory. WARNING: CPU: 3 PID: 1273 at lib/refcount.c:22 refcount_warn_saturate+0xae/0x1d0 Modules linked in: qrtr(+) bochs drm_shmem_helper ... Call Trace: qrtr_reset_ports net/qrtr/af_qrtr.c:768 [inline] [qrtr] __qrtr_bind.isra.0+0x48b/0x570 net/qrtr/af_qrtr.c:805 [qrtr] qrtr_bind+0x17d/0x210 net/qrtr/af_qrtr.c:901 [qrtr] kernel_bind+0xe4/0x120 net/socket.c:3592 qrtr_ns_init+0x1a6/0x380 net/qrtr/ns.c:715 [qrtr] qrtr_proto_init+0x3b/0xff0 net/qrtr/af_qrtr.c:169 [qrtr] do_one_initcall+0xf5/0x5e0 init/main.c:1283 ...
Fix this by deferring the reference count decrement until after the xa_erase() and the synchronize_rcu() complete.
(Note: The v1 of this patch incorrectly replaced __sock_put() with sock_put(). As Simon Horman pointed out, the callers of qrtr_port_remove() still hold a reference to the socket, so freeing the socket memory here would lead to a subsequent UAF in the caller. Thus, the __sock_put() is kept, but only repositioned to close the RCU race.)
{
"affected": [],
"aliases": [
"CVE-2026-52947"
],
"database_specific": {
"cwe_ids": [
"CWE-416"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-06-24T17:17:04Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: qrtr: fix refcount saturation and potential UAF in qrtr_port_remove\n\nIn qrtr_port_remove(), the socket reference count is decremented via\n__sock_put() before the port is removed from the qrtr_ports XArray and\nbefore the RCU grace period elapses.\n\nThis breaks the fundamental RCU update paradigm. It exposes a race\nwindow where a concurrent RCU reader (such as qrtr_reset_ports() or\nqrtr_port_lookup()) can obtain a pointer to the socket from the XArray,\nand attempt to call sock_hold() on a socket whose reference count has\nalready dropped to zero.\n\nThis exact race condition was hit during syzkaller fuzzing, leading to\nthe following refcount saturation warning and a potential Use-After-Free:\n\n refcount_t: saturated; leaking memory.\n WARNING: CPU: 3 PID: 1273 at lib/refcount.c:22 refcount_warn_saturate+0xae/0x1d0\n Modules linked in: qrtr(+) bochs drm_shmem_helper ...\n Call Trace:\n \u003cTASK\u003e\n qrtr_reset_ports net/qrtr/af_qrtr.c:768 [inline] [qrtr]\n __qrtr_bind.isra.0+0x48b/0x570 net/qrtr/af_qrtr.c:805 [qrtr]\n qrtr_bind+0x17d/0x210 net/qrtr/af_qrtr.c:901 [qrtr]\n kernel_bind+0xe4/0x120 net/socket.c:3592\n qrtr_ns_init+0x1a6/0x380 net/qrtr/ns.c:715 [qrtr]\n qrtr_proto_init+0x3b/0xff0 net/qrtr/af_qrtr.c:169 [qrtr]\n do_one_initcall+0xf5/0x5e0 init/main.c:1283\n ...\n \u003c/TASK\u003e\n\nFix this by deferring the reference count decrement until after the\nxa_erase() and the synchronize_rcu() complete.\n\n(Note: The v1 of this patch incorrectly replaced __sock_put() with\nsock_put(). As Simon Horman pointed out, the callers of qrtr_port_remove()\nstill hold a reference to the socket, so freeing the socket memory here\nwould lead to a subsequent UAF in the caller. Thus, the __sock_put() is\nkept, but only repositioned to close the RCU race.)",
"id": "GHSA-49c8-7mpf-m266",
"modified": "2026-06-28T09:31:37Z",
"published": "2026-06-24T18:32:41Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-52947"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/03bfa95e452e2b6ccd76a332060ae4feaf5ad84d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2047c2aa0963bb2872fd722300a15bcb441a4c00"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2aa4c12723fe432e623462a3be42a197a128722b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3b20ec8f31e8a6a6782243f473b0abd3463621df"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/474293d90880622fde9d2430fb0165767090f7b3"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7de2d447072be3b1a76793f034432338fc9c494b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a2171131ecda1ed61a594a1eb715e75fdad0fef5"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ab269990ed58143a92a263be1bee626d82ac03da"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
}
]
}
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