CVE-2026-89507

Status: UPDATED  |  Advisory ID: CVE-2026-89507

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

RDMA/ucma: Lock the handler in ucma_write_cm_event()

ctx->file may only be changed under the handler lock and the xa_lock, which

is what stops uevents being queued for a ctx while ucma_migrate_id() moves

it to another file. The CM core takes that lock before invoking

ucma_event_handler(), but the write() paths that queue uevents themselves

do not.

ucma_write_cm_event() re-reads ctx->file for each of its four dereferences,

so ucma_migrate_id() can swap it mid-sequence:

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 */

The window is the mutex_lock() itself: the writer sleeps in it while the

migration reassigns ctx->file. The list_add_tail() then runs on file B's

event_list holding only file A's mutex:

list_add corruption. prev->next should be next (ffff888101320f30),

but was ffff88814a08c418. (prev=ffff88814a075c18).

kernel BUG at lib/list_debug.c:32!

Call Trace:

ucma_write_cm_event+0x36e/0x5e0

and file A's mut is left held forever, wedging its next writer in D state.

The uevent is also stranded on a list ucma_cleanup_ctx_events() will not

walk, so it outlives its context. /dev/infiniband/rdma_cm is 0666 and no

RDMA device is involved, so an unprivileged user reaches all of this.

Take the handler lock, as ucma_cleanup_mc_events() does; ctx->cm_id is

pinned by the ucma_get_ctx() reference. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References