UBUNTU-CVE-2026-89507: High severity ubuntu/linux-hwe-edge vulnerability

In the Linux kernel, the following vulnerability has been resolved: RDMA/ucma: Lock the handler in ucmawritecmevent() ctx->file may only be changed under the handler lock and the xalock, which is what stops uevents being queued for a ctx while ucmamigrateid() moves it to another file. The CM core takes that lock before invoking ucmaeventhandler(), but the write() paths that queue uevents themselves do not. ucmawritecmevent() re-reads ctx->file for each of its four dereferences, so ucmamigrateid() can swap it mid-sequence: mutexlock(&ctx->file->mut); / file A / listaddtail(&uevent->list, &ctx->file->eventlist); / file B / mutexunlock(&ctx->file->mut); / file B / wakeupinterruptible(&ctx->file->pollwait); / file B / The window is the mutexlock() itself: the writer sleeps in it while the migration reassigns ctx->file. The listaddtail() then runs on file B's eventlist holding only file A's mutex: listadd corruption. prev->next should be next (ffff888101320f30), but was ffff88814a08c418. (prev=ffff88814a075c18). kernel BUG at lib/listdebug.c:32! Call Trace: ucmawritecmevent+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 ucmacleanupctxevents() will not walk, so it outlives its context. /dev/infiniband/rdmacm is 0666 and no RDMA device is involved, so an unprivileged user reaches all of this. Take the handler lock, as ucmacleanupmcevents() does; ctx->cmid is pinned by the ucmagetctx() reference.