GHSA-R924-QJ9J-26C5
Vulnerability from github – Published: 2026-09-11 21:31 – Updated: 2026-09-14 15:32In the Linux kernel, the following vulnerability has been resolved:
RDMA/ucma: Lock the handler in ucma_set_ib_path()
ucma_set_ib_path() calls ucma_event_handler() straight from the write() path, without the handler lock that keeps ctx->file stable while a uevent is queued. The handler re-reads ctx->file for every dereference:
mutex_lock(&ctx->file->mut); /* file A */
list_add_tail(&uevent->list, &ctx->file->event_list); /* file B */
mutex_unlock(&ctx->file->mut); /* file B */
wake_up_interruptible(&ctx->file->poll_wait); /* file B */
A concurrent ucma_migrate_id() reassigns ctx->file while the SET_OPTION caller sleeps in mutex_lock(), so the list_add_tail() lands on file B's event_list while only file A's mutex is held, racing every other user of that list:
BUG: KASAN: slab-use-after-free in __list_add_valid_or_report+0x1aa/0x1c0 Read of size 8 at addr ffff888153c6a418 by task poc_corr/486 Call Trace: __list_add_valid_or_report+0x1aa/0x1c0 ucma_event_handler+0x1be/0xc00 ucma_set_ib_path+0x45e/0x710 ucma_set_option+0x32e/0x590 ucma_write+0x1f9/0x330 Allocated by task 505: ucma_write_cm_event+0x1a1/0x660 Freed by task 505: kfree+0x1da/0x4c0 ucma_get_event+0x5d5/0x7e0
The freed object is a ucma_event that another thread dequeued from file B's list under file B's mutex. File A's mut is left held on top of that, wedging its next writer in uninterruptible sleep.
This path needs a bound and address-resolved cm_id, so it requires an RDMA device to be present.
Take the handler lock around the call.
{
"affected": [],
"aliases": [
"CVE-2026-89508"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-09-11T20:19:33Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nRDMA/ucma: Lock the handler in ucma_set_ib_path()\n\nucma_set_ib_path() calls ucma_event_handler() straight from the write()\npath, without the handler lock that keeps ctx-\u003efile stable while a uevent\nis queued. The handler re-reads ctx-\u003efile for every dereference:\n\n\tmutex_lock(\u0026ctx-\u003efile-\u003emut);\t\t\t/* file A */\n\tlist_add_tail(\u0026uevent-\u003elist, \u0026ctx-\u003efile-\u003eevent_list);\t/* file B */\n\tmutex_unlock(\u0026ctx-\u003efile-\u003emut);\t\t\t/* file B */\n\twake_up_interruptible(\u0026ctx-\u003efile-\u003epoll_wait);\t/* file B */\n\nA concurrent ucma_migrate_id() reassigns ctx-\u003efile while the SET_OPTION\ncaller sleeps in mutex_lock(), so the list_add_tail() lands on file B\u0027s\nevent_list while only file A\u0027s mutex is held, racing every other user of\nthat list:\n\n BUG: KASAN: slab-use-after-free in __list_add_valid_or_report+0x1aa/0x1c0\n Read of size 8 at addr ffff888153c6a418 by task poc_corr/486\n Call Trace:\n __list_add_valid_or_report+0x1aa/0x1c0\n ucma_event_handler+0x1be/0xc00\n ucma_set_ib_path+0x45e/0x710\n ucma_set_option+0x32e/0x590\n ucma_write+0x1f9/0x330\n Allocated by task 505:\n ucma_write_cm_event+0x1a1/0x660\n Freed by task 505:\n kfree+0x1da/0x4c0\n ucma_get_event+0x5d5/0x7e0\n\nThe freed object is a ucma_event that another thread dequeued from file B\u0027s\nlist under file B\u0027s mutex. File A\u0027s mut is left held on top of that,\nwedging its next writer in uninterruptible sleep.\n\nThis path needs a bound and address-resolved cm_id, so it requires an RDMA\ndevice to be present.\n\nTake the handler lock around the call.",
"id": "GHSA-r924-qj9j-26c5",
"modified": "2026-09-14T15:32:27Z",
"published": "2026-09-11T21:31:29Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-89508"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/28ac2dd416482d1c763c4af5d61af465b387fb50"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3dd07b369371a2f29e1c3caf1ade85bb92b4c551"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/43a7d8ae9f645dc00235cfa4bf57673c20b769f8"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/71dc206f2e2a645dac78879768762451aa1799f7"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/764586f8f6180084c5a7d622120f526acc6ce0c9"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a7f8d26e653ee43b0b572984b8ec544d3b3b6f3c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/b2da0d488a1c72956ebb0a57015ee8ee6a2f7748"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ecbe7d36dc2de07e5dfbb4a8ff5b315ab43de820"
}
],
"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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