{"id":"CVE-2026-64419","state":"PUBLISHED","title":"mm/shrinker: do not hold RCU lock in shrinker_debugfs_count_show()","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().","publishedAt":"2026-07-25T08:50:58.342Z","updatedAt":"2026-08-17T04:55:18.870Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"5035ebc644aec92d55d1bbfe042f35341e4bffb5","status":"affected","lessThan":"de5f69b8dae8698ac5e48dfcd30017887cdf4e5a","versionType":"git"},{"version":"5035ebc644aec92d55d1bbfe042f35341e4bffb5","status":"affected","lessThan":"e441cbfbd0eaa6404278e985033c33caba4db767","versionType":"git"},{"version":"5035ebc644aec92d55d1bbfe042f35341e4bffb5","status":"affected","lessThan":"2fed79f0fe8c8d28a972c290dbfd693c3546c8c4","versionType":"git"},{"version":"5035ebc644aec92d55d1bbfe042f35341e4bffb5","status":"affected","lessThan":"560e21e8ccff813e84d05f6500907c549a3d6985","versionType":"git"},{"version":"5035ebc644aec92d55d1bbfe042f35341e4bffb5","status":"affected","lessThan":"86237e56091e70f09c0fbf217f9d9c0e08f556c4","versionType":"git"},{"version":"5035ebc644aec92d55d1bbfe042f35341e4bffb5","status":"affected","lessThan":"b902890c62d200b3509cb5e09cf1e0a66553c128","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/shrinker_debug.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.0","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.96","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.39","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.4","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/shrinker_debug.c"]}],"references":["https://git.kernel.org/stable/c/de5f69b8dae8698ac5e48dfcd30017887cdf4e5a","https://git.kernel.org/stable/c/e441cbfbd0eaa6404278e985033c33caba4db767","https://git.kernel.org/stable/c/2fed79f0fe8c8d28a972c290dbfd693c3546c8c4","https://git.kernel.org/stable/c/560e21e8ccff813e84d05f6500907c549a3d6985","https://git.kernel.org/stable/c/86237e56091e70f09c0fbf217f9d9c0e08f556c4","https://git.kernel.org/stable/c/b902890c62d200b3509cb5e09cf1e0a66553c128"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:41.951Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/64xxx/CVE-2026-64419.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64419","state":"PUBLISHED","datePublished":"2026-07-25T08:50:58.342Z","dateUpdated":"2026-08-17T04:55:18.870Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T15:36:31.786Z"},"containers":{"cna":{"title":"mm/shrinker: do not hold RCU lock in shrinker_debugfs_count_show()","descriptions":[{"lang":"en","value":"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()."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"5035ebc644aec92d55d1bbfe042f35341e4bffb5","status":"affected","lessThan":"de5f69b8dae8698ac5e48dfcd30017887cdf4e5a","versionType":"git"},{"version":"5035ebc644aec92d55d1bbfe042f35341e4bffb5","status":"affected","lessThan":"e441cbfbd0eaa6404278e985033c33caba4db767","versionType":"git"},{"version":"5035ebc644aec92d55d1bbfe042f35341e4bffb5","status":"affected","lessThan":"2fed79f0fe8c8d28a972c290dbfd693c3546c8c4","versionType":"git"},{"version":"5035ebc644aec92d55d1bbfe042f35341e4bffb5","status":"affected","lessThan":"560e21e8ccff813e84d05f6500907c549a3d6985","versionType":"git"},{"version":"5035ebc644aec92d55d1bbfe042f35341e4bffb5","status":"affected","lessThan":"86237e56091e70f09c0fbf217f9d9c0e08f556c4","versionType":"git"},{"version":"5035ebc644aec92d55d1bbfe042f35341e4bffb5","status":"affected","lessThan":"b902890c62d200b3509cb5e09cf1e0a66553c128","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/shrinker_debug.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.0","versionType":"semver"},{"version":"6.1.178","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.145","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.96","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.39","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.4","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/shrinker_debug.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/de5f69b8dae8698ac5e48dfcd30017887cdf4e5a"},{"url":"https://git.kernel.org/stable/c/e441cbfbd0eaa6404278e985033c33caba4db767"},{"url":"https://git.kernel.org/stable/c/2fed79f0fe8c8d28a972c290dbfd693c3546c8c4"},{"url":"https://git.kernel.org/stable/c/560e21e8ccff813e84d05f6500907c549a3d6985"},{"url":"https://git.kernel.org/stable/c/86237e56091e70f09c0fbf217f9d9c0e08f556c4"},{"url":"https://git.kernel.org/stable/c/b902890c62d200b3509cb5e09cf1e0a66553c128"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-17T04:55:18.870Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"6.1.178"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"6.6.145"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"6.12.96"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"6.18.39"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"7.1.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.0","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}