CVE-2026-89508
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
In the Linux kernel, ucma_set_ib_path() called ucma_event_handler() from the write() path without the handler lock that keeps ctx->file stable while a uevent is queued. A concurrent ucma_migrate_id() could reassign ctx->file, causing list operations on another file's event_list without the correct mutex, leading to a use-after-free (detected by KASAN).
Risk Assessment
The vulnerability can cause kernel memory corruption (use-after-free), system crash (panic), or potentially privilege escalation by a local attacker. It requires an RDMA device to be present and the ability to invoke the relevant write/ioctl operations on the device.
Recommendation
Update the Linux kernel to a version containing the fix that takes the handler lock around the ucma_event_handler() call in ucma_set_ib_path(). If updating is not possible, restrict access to RDMA devices (/dev/infiniband/*) to trusted users.
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Original NVD description (English source)
In 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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS