GHSA-RJH9-M2M4-JGRV
Vulnerability from github – Published: 2026-10-06 09:31 – Updated: 2026-10-06 09:31In the Linux kernel, the following vulnerability has been resolved:
RDMA/rxe: validate access flags before swapping the MR's PD
rxe_rereg_user_mr() reassigns mr->ibmr.pd first and only then validates the IB_MR_REREG_ACCESS argument:
if (flags & IB_MR_REREG_PD) {
rxe_put(old_pd);
rxe_get(pd);
mr->ibmr.pd = ibpd;
}
if (flags & IB_MR_REREG_ACCESS) {
if (access & ~RXE_ACCESS_SUPPORTED_MR)
return ERR_PTR(-EOPNOTSUPP);
mr->access = access;
}
Both flags pass the entry check because RXE_MR_REREG_SUPPORTED is IB_MR_REREG_PD | IB_MR_REREG_ACCESS, so a caller can reach the access check with mr->ibmr.pd already reassigned.
mr->ibmr.pd is owned by the core, which adjusts pd->usecnt only on the success path: ib_uverbs_rereg_mr() jumps to put_new_uobj on a driver error without undoing the reassignment, so mr->pd == new_pd while the usecnts still charge the MR to orig_pd. ib_dereg_mr_user() then decrements new_pd, whose count can reach zero while a memory window still references it; uverbs_free_pd() frees the PD on that count alone and rxe_mw_cleanup() writes to freed memory:
BUG: KASAN: slab-use-after-free in __rxe_put+0x31/0xa0 Write of size 4 at addr ffff8881301dd690 by task rxe_poc/591 __rxe_put+0x31/0xa0 rxe_mw_cleanup+0x42/0x200 __rxe_cleanup+0x115/0x370 rxe_dealloc_mw+0x4c/0x80 Allocated by task 591: ib_uverbs_alloc_pd+0x258/0x540 Freed by task 591: ib_dealloc_pd_user+0x174/0x210 uverbs_free_pd+0x8d/0xc0 ib_uverbs_dealloc_pd+0x18e/0x1d0
Validate the access flags before mutating any state so the callback either applies every requested change or none.
{
"affected": [],
"aliases": [
"CVE-2026-98366"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-10-06T09:18:30Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nRDMA/rxe: validate access flags before swapping the MR\u0027s PD\n\nrxe_rereg_user_mr() reassigns mr-\u003eibmr.pd first and only then\nvalidates the IB_MR_REREG_ACCESS argument:\n\n\tif (flags \u0026 IB_MR_REREG_PD) {\n\t\trxe_put(old_pd);\n\t\trxe_get(pd);\n\t\tmr-\u003eibmr.pd = ibpd;\n\t}\n\n\tif (flags \u0026 IB_MR_REREG_ACCESS) {\n\t\tif (access \u0026 ~RXE_ACCESS_SUPPORTED_MR)\n\t\t\treturn ERR_PTR(-EOPNOTSUPP);\n\t\tmr-\u003eaccess = access;\n\t}\n\nBoth flags pass the entry check because RXE_MR_REREG_SUPPORTED is\nIB_MR_REREG_PD | IB_MR_REREG_ACCESS, so a caller can reach the access\ncheck with mr-\u003eibmr.pd already reassigned.\n\nmr-\u003eibmr.pd is owned by the core, which adjusts pd-\u003eusecnt only on the\nsuccess path: ib_uverbs_rereg_mr() jumps to put_new_uobj on a driver error\nwithout undoing the reassignment, so mr-\u003epd == new_pd while the usecnts\nstill charge the MR to orig_pd. ib_dereg_mr_user() then decrements\nnew_pd, whose count can reach zero while a memory window still references\nit; uverbs_free_pd() frees the PD on that count alone and rxe_mw_cleanup()\nwrites to freed memory:\n\n BUG: KASAN: slab-use-after-free in __rxe_put+0x31/0xa0\n Write of size 4 at addr ffff8881301dd690 by task rxe_poc/591\n __rxe_put+0x31/0xa0\n rxe_mw_cleanup+0x42/0x200\n __rxe_cleanup+0x115/0x370\n rxe_dealloc_mw+0x4c/0x80\n Allocated by task 591:\n ib_uverbs_alloc_pd+0x258/0x540\n Freed by task 591:\n ib_dealloc_pd_user+0x174/0x210\n uverbs_free_pd+0x8d/0xc0\n ib_uverbs_dealloc_pd+0x18e/0x1d0\n\nValidate the access flags before mutating any state so the callback either\napplies every requested change or none.",
"id": "GHSA-rjh9-m2m4-jgrv",
"modified": "2026-10-06T09:31:36Z",
"published": "2026-10-06T09:31:36Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98366"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/08f12745cb72981aa2cabe214af0c7a42a856f0a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/4dd7a53f1c5b44693c26dac4b9b5bd5bb9d604c8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/7230cc456d4bb2221c20c5f1d22b38b8576aa16f"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ae36a5b609ae79f4de966328b78d2584be9719a4"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/fe602c91a52e161ace4afd5bdb8f33270c554c6f"
}
],
"schema_version": "1.4.0",
"severity": []
}
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