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CVE-2026-89508
RDMA/ucma: Lock the handler in ucma_set_ib_path()
Published 2026-09-11 (37 days ago) by the Linux kernel CNA. Subsystem drivers/infiniband. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89508 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4841-1 · 2026-10-17 · text | 6.1.190-1 | Update the kernel and reboot. DLA-4841-1 shipped the fix on 2026-10-17, in 6.1.190-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
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.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/infiniband/core/ucma.c
- What this is
- INFINIBAND SUBSYSTEMMAINTAINERS section matched on drivers/infiniband/ · linux-rdma@vger.kernel.org · Supported
Show whether Debian builds this, per release
Not established. This site could not find the build rule for the affected file in the kernel trees Debian ships, so it has no answer about whether Debian compiles this code. Read that as unknown, never as absent.
- bookworm, trixie, forky, sid, bookworm · linux-6.12?
- ?
- not established - no Makefile entry for the affected file
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS
Signals
- Published
- 2026-09-11 (37 days ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.13%, higher than 2.0% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/infiniband
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.10 | 5.10.270 | 3dd07b369371 |
| 5.10 | 5.15.221 | b2da0d488a1c |
| 5.10 | 6.1.188 | a7f8d26e653e |
| 5.10 | 6.6.157 | 71dc206f2e2a |
| 5.10 | 6.12.109 | 764586f8f618 |
| 5.10 | 6.18.50 | 28ac2dd41648 |
| 5.10 | 7.2.4 | 43a7d8ae9f64 |
| 5.10 | 7.3 | ecbe7d36dc2d |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4841-1 | 2026-10-17 | bookworm 6.1.190-1 | tracker |
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The bug is reached only via write() on /dev/infiniband/rdma_cm (SET_OPTION -> ucma_set_option -> ucma_set_ib_path). A remote RDMA peer cannot invoke this path; in-kernel CM event delivery already holds the handler lock that this write path omitted.
- AC:LAttack complexity, low
- The attacker controls both sides of the race: one thread issues SET_OPTION (RDMA_OPTION_IB_PATH) while another MIGRATE_IDs the cm_id to a second fd and a third GET_EVENTs to free the uevent. The window is the mutex_lock() sleep in ucma_event_handler, which the attacker can widen, and it was reproduced by poc_corr.
- PR:LPrivileges required, low
- ucma is a miscdevice with mode 0666 and ucma_write() has no capability check. Any unprivileged local user can open /dev/infiniband/rdma_cm, CREATE_ID, resolve an address on an existing RDMA device, then issue SET_OPTION and MIGRATE_ID.
- UI:NUser interaction, none
- The attacker opens rdma_cm, creates and migrates their own cm_id, and issues the concurrent SET_OPTION and GET_EVENT writes themselves; no other user or administrator action is required.
- S:UScope, unchanged
- The use-after-free and list corruption are confined to host-kernel objects (ucma_event and file event_list). This is a standard local kernel compromise and does not cross a VM, IOMMU, or sandbox boundary.
- C:HConfidentiality impact, high
- The race is a slab use-after-free of struct ucma_event (KASAN in __list_add_valid_or_report after GET_EVENT kfree). Reclaiming the freed object gives the attacker control over list pointers and event contents, enabling disclosure of kernel memory.
- I:HIntegrity impact, high
- list_add_tail runs on file B's event_list while only file A's mutex is held, corrupting list pointers. Combined with UAF reclaim of ucma_event, this is a classic kernel list-unlink arbitrary-write primitive suitable for control-flow hijacking.
- A:HAvailability impact, high
- The UAF and list_debug BUG can oops the kernel, and the mismatched mutex_unlock leaves file A's mut held so the next writer sleeps uninterruptibly in D state, hanging the system.