In the Linux kernel, the following vulnerability has been resolved:
mm: shrinker: fix NULL pointer dereference in debugfs
shrinker_debugfs_add() creates both "count" and "scan" debugfs files unconditionally.
That assumes every shrinker implements both count_objects() and scan_objects(), which is not guaranteed. For example, the xen-backend shrinker sets count_objects() but leaves scan_objects() NULL, so writing to its scan file calls through a NULL function pointer and panics the kernel:
BUG: kernel NULL pointer dereference, address: 0000000000000000 RIP: 0010:0x0 Code: Unable to access opcode bytes at 0xffffffffffffffd6. Call Trace: <TASK> shrinker_debugfs_scan_write+0x12e/0x270 full_proxy_write+0x5f/0x90 vfs_write+0xde/0x420 ? filp_flush+0x75/0x90 ? filp_close+0x1d/0x30 ? do_dup2+0xb8/0x120 ksys_write+0x68/0xf0 ? filp_flush+0x75/0x90 do_syscall_64+0xb3/0x5b0 entry_SYSCALL_64_after_hwframe+0x76/0x7e
The count path has the same issue in principle if a shrinker omits count_objects().
To fix it, only create "count" and "scan" debugfs files when the corresponding callbacks are present.
CVSS Details
- CVSS 3.1 Base Score: 5.5
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Debian | — | Upgrade linux-6.1Upgrade linuxUpgrade linux-6.12 | Jul 28, 2026 | Jul 28, 2026 |
| Ubuntu | — | Upgrade linux-image-generic-hwe-26.04Upgrade linux-image-generic-hwe-24.04Upgrade linux-image-realtime-64kUpgrade linux-image-nvidia-64k-7.0Upgrade linux-image-genericUpgrade linux-image-nvidia-bos-7.0Upgrade linux-image-7.0.0-1013-oemUpgrade linux-image-generic-64kUpgrade linux-image-gkeUpgrade linux-image-7.0.0-1012-aws-64kUpgrade linux-image-7.0.0-1013-ibmUpgrade linux-image-gcpUpgrade linux-image-gcp-64k-7.0Upgrade linux-image-generic-64k-7.0Upgrade linux-image-gke-64k-hwe-26.04Upgrade linux-image-realtime-64k-hwe-26.04Upgrade linux-image-raspi-realtimeUpgrade linux-image-7.0.0-1006-gke-64kUpgrade linux-image-nvidia-64kUpgrade linux-image-7.0.0-31-generic-64kUpgrade linux-image-realtime-hwe-26.04Upgrade linux-image-7.0.0-1011-gcpUpgrade linux-image-generic-7.0Upgrade linux-image-7.0.0-2018-nvidia-bos-64kUpgrade linux-image-7.0.0-1019-raspi-realtimeUpgrade linux-image-oem-7.0Upgrade linux-image-virtualUpgrade linux-image-virtual-hwe-24.04Upgrade linux-image-aws-64kUpgrade linux-image-ibm-7.0Upgrade linux-image-nvidia-bos-64kUpgrade linux-image-nvidia-64k-hwe-26.04Upgrade linux-image-7.0.0-31-genericUpgrade linux-image-nvidia-hwe-26.04Upgrade linux-image-7.0.0-2018-nvidia-bosUpgrade linux-image-realtimeUpgrade linux-image-gke-64k-7.0Upgrade linux-image-7.0.0-1018-nvidia-64kUpgrade linux-image-aws-64k-7.0Upgrade linux-image-gcp-64kUpgrade linux-image-oem-26.04Upgrade linux-image-virtual-7.0Upgrade linux-image-realtime-7.0Upgrade linux-image-nvidia-bosUpgrade linux-image-virtual-hwe-26.04Upgrade linux-image-gcp-7.0Upgrade linux-image-7.0.0-1018-nvidiaUpgrade linux-image-nvidia-bos-64k-7.0Upgrade linux-image-7.0.0-1012-awsUpgrade linux-image-oem-26.04bUpgrade linux-image-awsUpgrade linux-image-7.0.0-1006-gkeUpgrade linux-image-raspi-7.0Upgrade linux-image-oem-26.04aUpgrade linux-image-7.0.0-31-realtime-64kUpgrade linux-image-realtime-64k-7.0Upgrade linux-image-generic-64k-hwe-24.04Upgrade linux-image-7.0.0-1019-raspiUpgrade linux-image-ibmUpgrade linux-image-gke-hwe-26.04Upgrade linux-image-aws-7.0Upgrade linux-image-gke-7.0Upgrade linux-image-raspiUpgrade linux-image-nvidia-7.0Upgrade linux-image-7.0.0-1011-gcp-64kUpgrade linux-image-nvidiaUpgrade linux-image-raspi-realtime-7.0Upgrade linux-image-generic-64k-hwe-26.04Upgrade linux-image-7.0.0-31-realtimeUpgrade linux-image-gke-64k | Sep 14, 2026 | Sep 7, 2026 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | Jul 31, 2026 | Jul 25, 2026 |
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