CVE-2026-64417 Details
Description
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.
A vulnerability in the Linux kernel's handling of shrinker debug files can lead to a NULL pointer dereference. The issue arises because the function 'shrinker_debugfs_add()' creates 'count' and 'scan' debugfs files without checking if the corresponding callback functions are implemented by the shrinker. This can cause a kernel panic. For instance, the xen-backend shrinker provides a count function but leaves the scan function NULL. Writing to the scan file then attempts to call a non-existent function, resulting in a NULL pointer dereference and a kernel panic. The same issue can occur with the count file if a shrinker omits the count_objects() implementation.
The vulnerability has been addressed by modifying the 'shrinker_debugfs_add()' function to only create 'count' and 'scan' debugfs files when the corresponding callback functions are present. Users should upgrade to the patched version of the Linux kernel.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
No SSVC data is available for this CVE.
References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://git.kernel.org/stable/c/006467ab932698612398f853344a7405164541f4 | kernel.org | Patch |
| https://git.kernel.org/stable/c/09d2407985b8ce3e831f9d4310fe7ac06a6b3ae9 | kernel.org | Patch |
| https://git.kernel.org/stable/c/36f8534f461222291a74156ab91f3ba9f09b6f93 | kernel.org | Patch |
| https://git.kernel.org/stable/c/b9beed2322f3538b0d2d53307062da4102b8d8d8 | kernel.org | Patch |
| https://git.kernel.org/stable/c/e30453c61e185e914fde83c650e268067b140218 | kernel.org | Patch |
| https://git.kernel.org/stable/c/ebb45c2648b1f60715fd283700f651e05e431231 | kernel.org | Patch |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-476 | NULL Pointer Dereference | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| linux linux kernel | >= 6.0, < 6.1.178 >= 6.2, < 6.6.145 >= 6.7, < 6.12.96 >= 6.13, < 6.18.39 >= 6.19, < 7.1.4 7.2 rc1 7.2 rc2 |
CPE
Remediation
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Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 4, 2026 | Initial Analysis | [email protected] |
| Aug 17, 2026 | CVE Modified | kernel.org |
| Jul 25, 2026 | New CVE Received | kernel.org |