{"id":"CVE-2026-64417","summary":"mm: shrinker: fix NULL pointer dereference in debugfs","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm: shrinker: fix NULL pointer dereference in debugfs\n\nshrinker_debugfs_add() creates both \"count\" and \"scan\" debugfs files\nunconditionally.\n\nThat assumes every shrinker implements both count_objects() and\nscan_objects(), which is not guaranteed.  For example, the xen-backend\nshrinker sets count_objects() but leaves scan_objects() NULL, so writing\nto its scan file calls through a NULL function pointer and panics the\nkernel:\n\nBUG: kernel NULL pointer dereference, address: 0000000000000000\nRIP: 0010:0x0\nCode: Unable to access opcode bytes at 0xffffffffffffffd6.\nCall Trace:\n \u003cTASK\u003e\n shrinker_debugfs_scan_write+0x12e/0x270\n full_proxy_write+0x5f/0x90\n vfs_write+0xde/0x420\n ? filp_flush+0x75/0x90\n ? filp_close+0x1d/0x30\n ? do_dup2+0xb8/0x120\n ksys_write+0x68/0xf0\n ? filp_flush+0x75/0x90\n do_syscall_64+0xb3/0x5b0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nThe count path has the same issue in principle if a shrinker omits\ncount_objects().\n\nTo fix it, only create \"count\" and \"scan\" debugfs files when the\ncorresponding callbacks are present.","modified":"2026-07-27T04:03:19.377986193Z","published":"2026-07-25T08:50:56.800Z","database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64417.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/006467ab932698612398f853344a7405164541f4"},{"type":"WEB","url":"https://git.kernel.org/stable/c/09d2407985b8ce3e831f9d4310fe7ac06a6b3ae9"},{"type":"WEB","url":"https://git.kernel.org/stable/c/36f8534f461222291a74156ab91f3ba9f09b6f93"},{"type":"WEB","url":"https://git.kernel.org/stable/c/b9beed2322f3538b0d2d53307062da4102b8d8d8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e30453c61e185e914fde83c650e268067b140218"},{"type":"WEB","url":"https://git.kernel.org/stable/c/ebb45c2648b1f60715fd283700f651e05e431231"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64417.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64417"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"bbf535fd6f06b94b9d07ed6f09397a936d4a58d8"},{"fixed":"ebb45c2648b1f60715fd283700f651e05e431231"},{"fixed":"09d2407985b8ce3e831f9d4310fe7ac06a6b3ae9"},{"fixed":"36f8534f461222291a74156ab91f3ba9f09b6f93"},{"fixed":"006467ab932698612398f853344a7405164541f4"},{"fixed":"b9beed2322f3538b0d2d53307062da4102b8d8d8"},{"fixed":"e30453c61e185e914fde83c650e268067b140218"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64417.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"6.0.0"},{"fixed":"6.1.178"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.145"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.96"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.39"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64417.json"}}],"schema_version":"1.7.5"}