{"id":"CVE-2026-99179","aliases":[],"title":"watch_queue: Fix note pool publication race in watch_queue_set_size()","titleSource":"Linux","descriptionSource":"Linux","products":[{"vendor":"Linux","name":"Linux","platforms":[],"versions":[{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"811fb6d0b07605e8e8d93bde8748be4b3028809a","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"9e73a6754457ffed8399b835552013b9363e51d1","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"5e531d62f1f8834faf7a4eed0d41105cf6570a8f","versionType":"git"}],"defaultStatus":"unaffected","source":"Linux","url":"https://www.cve.org/CVERecord?id=CVE-2026-99179"},{"vendor":"Linux","name":"Linux","platforms":[],"versions":[{"version":"5.8","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.8","versionType":"semver"},{"version":"6.18.59","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.13","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"defaultStatus":"affected","source":"Linux","url":"https://www.cve.org/CVERecord?id=CVE-2026-99179"}],"remediation":[],"description":"In the Linux kernel, the following vulnerability has been resolved:\n\nwatch_queue: Fix note pool publication race in watch_queue_set_size()\n\nThere is a race between watch_queue_set_size() and post_one_notification().\nwatch_queue_set_size() publishes wqueue->notes, notes_bitmap, nr_pages and\nnr_notes with plain stores, and post_one_notification() reads them with\nplain loads under a different lock, so nothing orders the four stores\nagainst the poster's loads: depending on the build, notes can be stored\nlast (gcc 14 on x86-64 does this).  Since keyctl_watch_key() lets a watch\nattach to a queue before it is sized, post_one_notification() can already\nbe running on another CPU at that moment: it reads nr_notes > 0, passes\nits bounds check, and then reads notes while it is still NULL,\ndereferencing notes[0].\n\nAn unprivileged user triggers this reliably by watching one of its own\nkeys through a notification pipe and racing ioctl(IOC_WATCH_QUEUE_SET_SIZE)\non that pipe against keyctl(KEYCTL_SETPERM) on the key from another CPU,\ntriggering:\n\n  BUG: kernel NULL pointer dereference, address: 0000000000000000\n  RIP: 0010:post_one_notification.isra.0+0xa2/0x1e0\n  Call Trace:\n   __post_watch_notification+0x148/0x180\n   keyctl_setperm_key+0x119/0x130\n   do_syscall_64+0x108/0x4c0\n   entry_SYSCALL_64_after_hwframe+0x77/0x7f\n  Kernel panic - not syncing: Fatal exception in interrupt\n\nFix this by publishing nr_notes last with smp_store_release(), and by\nreading it once with smp_load_acquire() in post_one_notification() before\nthe bitmap and the page array are touched.  A poster that observes a\nnon-zero nr_notes then also observes the pool behind it; one that observes\nzero drops the notification as before.","severity":"unknown","score":null,"published":"2026-10-28T10:35:32.734Z","modified":"2026-10-28T10:35:32.734Z","withdrawn":false,"knownExploited":false,"affected":[],"references":["https://git.kernel.org/stable/c/811fb6d0b07605e8e8d93bde8748be4b3028809a","https://git.kernel.org/stable/c/9e73a6754457ffed8399b835552013b9363e51d1","https://git.kernel.org/stable/c/5e531d62f1f8834faf7a4eed0d41105cf6570a8f"],"sources":[{"name":"CVE","id":"CVE-2026-99179","modified":"2026-10-28T10:35:32.734Z","url":"https://www.cve.org/CVERecord?id=CVE-2026-99179"}],"assessments":[],"sourceAffected":[],"kev":{"status":"not-listed","checkedAt":"2026-10-29T00:50:31.383Z"},"coverage":[{"source":"NVD","status":"not-checked"},{"source":"GHSA","status":"not-checked"},{"source":"EUVD","status":"not-checked"},{"source":"EPSS","status":"not-checked"}],"evidence":[]}