{"id":"CVE-2026-99179","state":"PUBLISHED","title":"watch_queue: Fix note pool publication race in watch_queue_set_size()","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.","publishedAt":"2026-10-28T10:35:32.734Z","updatedAt":"2026-10-30T12:42:42.438Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"2137d487b25eefa862be70de489b64f4c679fe1f","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"6aaa6c1a1b61aae332d6e7e0083140b86ea51e14","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"4b20867d80e7e91fb7db531f34035d91591ba405","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"da52e5fcb2cae6acdc0d5722ff83499f8232b9d1","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"f94c45f83e688e41dfe1b3a589806a0a25567260","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"811fb6d0b07605e8e8d93bde8748be4b3028809a","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"9e73a6754457ffed8399b835552013b9363e51d1","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"5e531d62f1f8834faf7a4eed0d41105cf6570a8f","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/watch_queue.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.8","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.8","versionType":"semver"},{"version":"5.10.273","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.224","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.161","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.115","status":"unaffected","lessThanOrEqual":"6.12.*","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"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/watch_queue.c"]}],"references":["https://git.kernel.org/stable/c/2137d487b25eefa862be70de489b64f4c679fe1f","https://git.kernel.org/stable/c/6aaa6c1a1b61aae332d6e7e0083140b86ea51e14","https://git.kernel.org/stable/c/4b20867d80e7e91fb7db531f34035d91591ba405","https://git.kernel.org/stable/c/da52e5fcb2cae6acdc0d5722ff83499f8232b9d1","https://git.kernel.org/stable/c/f94c45f83e688e41dfe1b3a589806a0a25567260","https://git.kernel.org/stable/c/811fb6d0b07605e8e8d93bde8748be4b3028809a","https://git.kernel.org/stable/c/9e73a6754457ffed8399b835552013b9363e51d1","https://git.kernel.org/stable/c/5e531d62f1f8834faf7a4eed0d41105cf6570a8f"],"weaknesses":[],"ingestedAt":"2026-10-30T13:02:04.640Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/99xxx/CVE-2026-99179.json","commit":"cb14bf1b43b0c9f05f7f40eae2246263fd430780","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-99179","state":"PUBLISHED","datePublished":"2026-10-28T10:35:32.734Z","dateUpdated":"2026-10-30T12:42:42.438Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.399Z"},"containers":{"cna":{"title":"watch_queue: Fix note pool publication race in watch_queue_set_size()","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"2137d487b25eefa862be70de489b64f4c679fe1f","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"6aaa6c1a1b61aae332d6e7e0083140b86ea51e14","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"4b20867d80e7e91fb7db531f34035d91591ba405","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"da52e5fcb2cae6acdc0d5722ff83499f8232b9d1","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"f94c45f83e688e41dfe1b3a589806a0a25567260","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"811fb6d0b07605e8e8d93bde8748be4b3028809a","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"9e73a6754457ffed8399b835552013b9363e51d1","versionType":"git"},{"version":"c73be61cede5882f9605a852414db559c0ebedfd","status":"affected","lessThan":"5e531d62f1f8834faf7a4eed0d41105cf6570a8f","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/watch_queue.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.8","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.8","versionType":"semver"},{"version":"5.10.273","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.224","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.161","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.115","status":"unaffected","lessThanOrEqual":"6.12.*","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"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/watch_queue.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/2137d487b25eefa862be70de489b64f4c679fe1f"},{"url":"https://git.kernel.org/stable/c/6aaa6c1a1b61aae332d6e7e0083140b86ea51e14"},{"url":"https://git.kernel.org/stable/c/4b20867d80e7e91fb7db531f34035d91591ba405"},{"url":"https://git.kernel.org/stable/c/da52e5fcb2cae6acdc0d5722ff83499f8232b9d1"},{"url":"https://git.kernel.org/stable/c/f94c45f83e688e41dfe1b3a589806a0a25567260"},{"url":"https://git.kernel.org/stable/c/811fb6d0b07605e8e8d93bde8748be4b3028809a"},{"url":"https://git.kernel.org/stable/c/9e73a6754457ffed8399b835552013b9363e51d1"},{"url":"https://git.kernel.org/stable/c/5e531d62f1f8834faf7a4eed0d41105cf6570a8f"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:42:42.438Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.8","versionEndExcluding":"5.10.273"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.8","versionEndExcluding":"5.15.224"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.8","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.8","versionEndExcluding":"6.6.161"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.8","versionEndExcluding":"6.12.115"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.8","versionEndExcluding":"6.18.59"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.8","versionEndExcluding":"7.2.13"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.8","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}