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CVE-2026-63863
drm/gpusvm: Fix unbalanced unlock in drm_gpusvm_scan_mm()
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem drivers/gpu. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-63863 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
There is a unbalanced lock/unlock to gpusvm notifier lock: [ 931.045868] ===================================== [ 931.046509] WARNING: bad unlock balance detected! [ 931.047149] 6.19.0-rc6+xe-**************** #9 Tainted: G U [ 931.048150] ------------------------------------- [ 931.048790] kworker/u5:0/51 is trying to release lock (&gpusvm->notifier_lock) at: [ 931.049801] [<ffffffffa090c0d8>] drm_gpusvm_scan_mm+0x188/0x460 [drm_gpusvm_helper] [ 931.050802] but there are no more locks to release! [ 931.051463] The drm_gpusvm_notifier_unlock() sits under err_free label and the first jump to err_free is just before calling the drm_gpusvm_notifier_lock() causing unbalanced unlock.
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/gpu/drm/drm_gpusvm.c
- What this is
- DRM DRIVERS AND MISC GPU PATCHESMAINTAINERS section matched on drivers/gpu/drm/ · Maintained
- Kernel module
- drm_gpusvm_helper
Check it on the machine
grep -w CONFIG_DRM_GPUSVM /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w drm_gpusvm_helperPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed. The build rule could not be established for 2 releases, so nothing is claimed about those.
- bookworm, trixie?
- forky, sidMnot built on amd64/cloud-amd64, arm64/arm64-16k, arm64/cloud-arm64, loong64/loong64, ppc64el/powerpc64le-64k, s390x/s390x
- ?
- not established - no Makefile entry for the affected file
- M
- a module where it is built at all; some flavours do not build it
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.
- Build switch
- CONFIG_DRM_GPUSVM
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 kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-07-19 (3 months ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 5.4% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/gpu
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 7.0 | 7.0.10 | 8efaa47a8716 |
| 7.0 | 7.1 | d287dee565c3 |
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 vulnerable code is only reached via Intel Xe DRM ioctls (DRM_XE_VM_BIND prefetch, GPU page-fault handling) on /dev/dri/renderD*, which require local access to the GPU device node.
- AC:LAttack complexity, low
- An attacker can reliably trigger the bug by racing CPU memory operations (munmap/mremap/mprotect) against GPU SVM VRAM migration to force hmm_range_fault() to return an error or time out on -EBUSY, hitting the err_free path without holding notifier_lock.
- PR:LPrivileges required, low
- Exploitation requires opening the DRM render node (DRM_RENDER_ALLOW), which is available to unprivileged users in the render group on typical desktop and cloud GPU instances, not root or capabilities.
- UI:NUser interaction, none
- No victim interaction is required; the attacker triggers the condition through their own GPU VM bindings, compute submissions, and concurrent memory manipulation.
- S:CScope, changed
- Corrupting notifier_lock breaks the documented IOMMU security model for GPU SVM, allowing GPU DMA operations to proceed without proper invalidation synchronization and potentially accessing host memory outside the attacker's GPU context.
- C:HConfidentiality impact, high
- Rwsem corruption from the spurious unlock can desynchronize invalidation from migration, enabling races where the GPU reads stale or freed pages that may have been reallocated, constituting arbitrary memory disclosure.
- I:HIntegrity impact, high
- The same lock corruption can allow GPU DMA writes to pages during or after invalidation races, providing a path to arbitrary memory corruption and potential privilege escalation.
- A:HAvailability impact, high
- The bug triggers a kernel lockdep warning ("bad unlock balance detected") and rwsem corruption can cause kernel oops, hangs, or panic during subsequent notifier_lock operations.