{"id":"CVE-2026-64419","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-64419","generatedAt":"2026-10-28T02:18:57.806Z","title":"In the Linux kernel, the following vulnerability has been resolved: mm/shrinker: do not hold RCU lock in shrinker_debugfs_count_show() Reading the debugfs \"count\" file of a memcg-aware shrinker can sleep inside an RCU read-side critical section: BUG:…","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/shrinker: do not hold RCU lock in shrinker_debugfs_count_show()\n\nReading the debugfs \"count\" file of a memcg-aware shrinker can sleep\ninside an RCU read-side critical section:\n\n  BUG: sleeping function called from invalid context at kernel/cgroup/rstat.c:421\n  RCU nest depth: 1, expected: 0\n   css_rstat_flush\n   mem_cgroup_flush_stats\n   zswap_shrinker_count\n   shrinker_debugfs_count_show\n\nshrinker_debugfs_count_show() invokes the ->count_objects() callback under\nrcu_read_lock().  The zswap callback flushes memcg stats via\ncss_rstat_flush(), which may sleep, so it must not run under RCU.\n\nThe RCU lock is not needed here.  mem_cgroup_iter() takes RCU internally\nand returns a memcg holding a css reference (dropped on the next iteration\nor by mem_cgroup_iter_break()), so the memcg stays alive without it.  The\nshrinker is kept alive by the open debugfs file: shrinker_free() removes\nthe debugfs entries via debugfs_remove_recursive(), which waits for\nin-flight readers to drain, before call_rcu(..., shrinker_free_rcu_cb). \nThe sibling \"scan\" handler already invokes the sleeping ->scan_objects()\ncallback with no RCU section.\n\nDrop the rcu_read_lock()/rcu_read_unlock().","published":"2026-07-25T10:17:26.000Z","lastModified":"2026-09-04T15:24:24.000Z","status":"Analyzed","sourceIdentifier":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","cvss":{"version":"3.1","score":5.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"},"cwe":[],"affected":["linux/linux kernel"],"epss":{"score":0.00123,"percentile":0.02009,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.12%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://git.kernel.org/stable/c/2fed79f0fe8c8d28a972c290dbfd693c3546c8c4","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/560e21e8ccff813e84d05f6500907c549a3d6985","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/86237e56091e70f09c0fbf217f9d9c0e08f556c4","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/b902890c62d200b3509cb5e09cf1e0a66553c128","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/de5f69b8dae8698ac5e48dfcd30017887cdf4e5a","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/e441cbfbd0eaa6404278e985033c33caba4db767","tags":["Patch"],"source":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-64419","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}