Look up another CVE · open CVE-2026-89805 in the interactive tracker
CVE-2026-89805
drm/pagemap: Fix folio allocation fallback and use-after-put
Published 2026-09-16 (33 days ago) by the Linux kernel CNA. Subsystem drivers/gpu. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-89805 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 | 7.2.6-1 | 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. |
The vulnerability
What the bug is
drm_pagemap_migrate_populate_ram_pfn() had two issues when populating RAM PFNs with higher-order folios: 1. The higher-order vma_alloc_folio()/folio_alloc() calls did not pass __GFP_NOWARN, so a THP allocation failure under memory pressure would spam the kernel log, and there was no fallback path despite a TODO comment stating one was needed. Add __GFP_NOWARN to the higher-order allocation and, on failure, fall back to order-0 allocations for the entire range originally covered by the failed higher-order allocation, leaving MIGRATE_PFN_COMPOUND unset for those PFNs. 2. In the free_pages error path, order was computed via folio_order(page_folio(page)) *after* put_page(page) had already dropped the reference, resulting in a use-after-free/put when that was the last reference on the page. Compute order before releasing the page. Introducing the fallback in 1. also requires the source page array handed to ->copy_to_ram() to be built differently. Both callers only populated the entry at the head of each source folio, relying on the copy callback to derive the rest of the folio from the order recorded in the matching drm_pagemap_addr. Once the destination has been demoted to order-0 folios the drm_pagemap_addr entries are per-page, so a source page is needed for every one of them; leaving them NULL makes the copy callback stop after the first page and the remainder of the range is never copied. The source folio is only split later, by migrate_vma_pages() / migrate_device_pages(), so its order cannot be used to detect the demotion - test the destination for MIGRATE_PFN_COMPOUND instead. Factor the array population out into drm_pagemap_migrate_populate_src_pages() and use it from both drm_pagemap_evict_to_ram() and __drm_pagemap_migrate_to_ram().
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_pagemap.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 -wE 'CONFIG_DRM_GPUSVM|CONFIG_ZONE_DEVICE' /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, armhf/armmp, armhf/armmp-lpae, 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 switches
- CONFIG_DRM_GPUSVM, CONFIG_ZONE_DEVICE
- Reads as
- all on means the file is compiled; any one off means it is not.
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
- 2026-09-16 (33 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
- 0.17%, 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 |
|---|---|---|
| 6.18 | 7.2.5 | 10e92e18e3da |
| 6.18 | 7.3 | df72e55e754c |
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 UAF is in drm_pagemap_migrate_populate_ram_pfn on the migrate-to-RAM path, reached from a local CPU fault on device-private SVM pages (do_swap_page → drm_pagemap_migrate_to_ram) or Xe TTM eviction (xe_svm_bo_evict → drm_pagemap_evict_to_ram), not from network packets.
- AC:LAttack complexity, low
- The attacker controls SVM setup and can force the free_pages path by failing a later GFP_HIGHUSER/THP allocation under self-induced memory pressure or fragmentation after earlier folios succeeded; the use-after-put then runs deterministically with no victim timing.
- PR:LPrivileges required, low
- DRM_IOCTL_XE_VM_CREATE and VM_BIND are DRM_RENDER_ALLOW with no capable() or DRM-master check. An unprivileged user with typical render/video-group access to /dev/dri/renderD* on an Intel Xe discrete GPU can create a fault-mode SVM VM and trigger migration.
- UI:NUser interaction, none
- The attacking process drives mmap, SVM bind/prefetch to VRAM, migrate-back via CPU access or VRAM eviction, and memory pressure itself; no separate victim action is required.
- S:UScope, unchanged
- The UAF corrupts host kernel page-allocator metadata in the same security authority. This is standard local kernel privilege escalation, not a KVM/Xen guest-to-host escape or IOMMU/DMA boundary bypass.
- C:HConfidentiality impact, high
- put_page() drops the last reference on the just-allocated folio, then folio_order(page_folio(page)) reads the freed page struct and may follow stale compound_info tail encoding, yielding an arbitrary kernel read of vmemmap/page flags.
- I:HIntegrity impact, high
- The same use-after-put lets reused or stale page flags supply an attacker-influenced order that skips remaining puts or corrupts the free loop, and a page-struct UAF is exploitable via buddy reuse for arbitrary kernel writes or control-flow hijack.
- A:HAvailability impact, high
- Accessing a freed or reused page struct can oops or panic, and a corrupted order that makes NR_PAGES() return 0 hangs in an infinite free_pages loop; any kernel UAF is high availability impact.