{"id":"CVE-2026-98981","revision":null,"records":[{"revision":"e768fd3e752548c2861e67ccf4311bcb","observedAt":"2026-10-24T16:17:04.479+00:00","statement":{"source":"cve-program","id":"CVE-2026-98981","aliases":[],"title":"namespace: unhash a dentry before detaching the mounts on it","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: unhash a dentry before detaching the mounts on it\n\nunlink(), rmdir() and rename() remove the entry from the filesystem,\ncall detach_mounts() on the entry with the inode locked and then call\nd_delete() once the inode is unlocked.\n\nThe thing is that between detach_mounts() and d_delete() the dentry is\nstill hashed and positive. But after detach_mounts() nothing covers the\ndentry anymore. A lookup that finds this dentry in the dcache can\nuncover what the mounts hid.\n\nThat's a problem when unlinking files or directories that are\nmountpoints in other mount namespaces. Everybody who had the underlying\nentry covered can race the detach_mount() call until d_delete() has run.\n\nThe race window isn't all that small. It encompasses namespace_unlock()\nwith a full synchronize_rcu_expedited() grace period and the\ninode_unlock() of the entry.\n\nIn my experiments three walkers that kept trying read an overmounted\nfile in 11938 of the 16140 unlinks that removed its mountpoint from a\nbind mount of the filesystem within a minute.\n\nFun fact, d_invalidate() has the same ordering problem but gets it\nright. It unhashes the dentry first and detaches the mounts afterwards.\nLet's do the same in __detach_mounts():\n\n- A lookup that hasn't found the dentry yet misses it in the dcache and\n waits for the directory lock that the caller holds until the name is\n gone for good.\n\n- A lockless lookup that found it already fails the mount_lock check\n while the dentry still counts as a mountpoint and the d_seq check once\n it doesn't, and retries.\n\nThis fixes the lockless path. We still need to fix the reference count\nlookup in a follow-up patch.\n\nSo d_drop() the dentry. The dentry stays positive and held but can't be\nfound anymore. Then proceed with the detach and unlink.\n\nReproducer:\n\nThe reads were counted with the program below, three walkers for 60 s\nin a VM with 4 CPUs. The race window is stretched with the debug patch\npasted here. fs.detach_race_walk_us sleeps in lookup_fast() once it\nfound a mountpoint dentry and before its mounts are crossed.\nfs.detach_race_unlink_us sleeps in vfs_unlink() between detach_mounts()\nand d_delete().\n\n // SPDX-License-Identifier: GPL-2.0\n /*\n * unlink_covered: unlink a file that is a mountpoint in a detached copy of\n * its mount, against lookups that open it through that copy.\n *\n * A is a tmpfs with the file f1 (content SECRET_F) and the plain file\n * MARK_A. A' is an open_tree(OPEN_TREE_CLONE) copy of A with MARK_A bound\n * on A'/f1, held through an O_PATH fd on its root once the tree fd is\n * closed. Walkers open f1 through that fd while the driver unlinks A/f1,\n * where nothing is mounted on it. A walker may read MARK_A or get ENOENT.\n * A read of SECRET_F is a hit: the name was found after its mount was\n * gone. The lockless walks use openat2(RESOLVE_CACHED).\n *\n * usage: unlink_covered [-t seconds] [-w walkers]\n */\n #ifndef _GNU_SOURCE\n #define _GNU_SOURCE\n #endif\n #include \n #include \n #include \n #include \n #include \n #include \n #include \n #include \n #include \n #include \n #include \n #include \n\n #ifndef __NR_open_tree\n #define __NR_open_tree 428\n #endif\n #ifndef __NR_move_mount\n #define __NR_move_mount 429\n #endif\n #ifndef __NR_openat2\n #define __NR_openat2 437\n #endif\n #ifndef OPEN_TREE_CLONE\n #define OPEN_TREE_CLONE 1\n #endif\n #ifndef OPEN_TREE_CLOEXEC\n #define OPEN_TREE_CLOEXEC O_CLOEXEC\n #endif\n #ifndef MOVE_MOUNT_F_EMPTY_PATH\n #define MOVE_MOUNT_F_EMPTY_PATH 0x00000004\n #endif\n\n #define WORK \"/tmp/uc\"\n #define ADIR WORK \"/A\"\n\n static int duration = 60, nwalkers = 3;\n static atomic_int stop, writer_waiting;\n static pthread_rwlock_t cur_lock = PTHREAD_RWLOCK_INITIALIZER;\n static int cur_fd = -1;\t\t/* the root of A', -1 wh\n---truncated---","state":0,"publishedAt":"2026-10-23T12:19:58.507+00:00","modifiedAt":"2026-10-24T14:09:49.642+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"unaffected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"fs/namespace.c\"\n ],\n \"versions\": [\n {\n \"version\": \"8ed936b5671bfb33d89bc60bdcc7cf0470ba52fe\",\n \"lessThan\": \"db90eecbde319527aa9480c039d32a0f5fe80574\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"8ed936b5671bfb33d89bc60bdcc7cf0470ba52fe\",\n \"lessThan\": \"8d71bfc9b3fc15d7103e82ea9dc5057541866e46\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"8ed936b5671bfb33d89bc60bdcc7cf0470ba52fe\",\n \"lessThan\": \"d29cd99db3db74cf3447be74d25740981789d461\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"8ed936b5671bfb33d89bc60bdcc7cf0470ba52fe\",\n \"lessThan\": \"8300de4aa5d09061bfcf2af5b52c0cdba3873185\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"8ed936b5671bfb33d89bc60bdcc7cf0470ba52fe\",\n \"lessThan\": \"528b383dc35d1e5caf64ddf5d35f983ae543b0d0\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n }\n ]\n }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"affected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"fs/namespace.c\"\n ],\n \"versions\": [\n {\n \"version\": \"3.18\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"3.18\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.160\",\n \"lessThanOrEqual\": \"6.6.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.114\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18.57\",\n \"lessThanOrEqual\": \"6.18.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.2.11\",\n \"lessThanOrEqual\": \"7.2.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.3\",\n \"lessThanOrEqual\": \"*\",\n \"status\": \"unaffected\",\n \"versionType\": \"original_commit_for_fix\"\n }\n ]\n }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H","score":8.8,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/db90eecbde319527aa9480c039d32a0f5fe80574","https://git.kernel.org/stable/c/8d71bfc9b3fc15d7103e82ea9dc5057541866e46","https://git.kernel.org/stable/c/d29cd99db3db74cf3447be74d25740981789d461","https://git.kernel.org/stable/c/8300de4aa5d09061bfcf2af5b52c0cdba3873185","https://git.kernel.org/stable/c/528b383dc35d1e5caf64ddf5d35f983ae543b0d0"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98981","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-98981","identifiers":["CVE-2026-98981"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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Not a global EUVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. No reader inventory is sent.","generation":"enrichment-43321610382942b8ad8c85917eab1546","complete":false,"records":4735,"lastAttemptAt":"2026-10-26T00:47:02.6516296+00:00","lastSuccessAt":"2026-10-24T23:18:49.862+00:00","error":"InvalidDataException","lastVerifiedAt":"2026-10-24T23:18:49.862+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":4764,"expectedIdentifiers":13474},{"source":"first-epss:nuget","scope":"FIRST EPSS for explicit CVE aliases in the collected public NuGet archive. Not a global EPSS backfill.","generation":"2026-10-26T00:46:57.9533087+00:00","complete":true,"records":1093,"lastAttemptAt":"2026-10-26T00:46:57.9533087+00:00","lastSuccessAt":"2026-10-26T00:46:58.1082168+00:00","error":null,"lastVerifiedAt":"2026-10-26T00:46:58.1082172+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null},{"source":"nvd","scope":"Rolling NVD lookups of CVE aliases in current public OSV archives; 500 identifiers per refresh, rechecked after 48 hours. Not a global NVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. No reader inventory is sent.","generation":"enrichment-204a3fb93a00487e8f7f36db01dc851d","complete":true,"records":13413,"lastAttemptAt":"2026-10-26T00:47:00.681998+00:00","lastSuccessAt":"2026-10-25T16:19:28.681+00:00","error":null,"lastVerifiedAt":"2026-10-25T16:19:28.681+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":13474,"expectedIdentifiers":13474},{"source":"osv:Go","scope":"Complete OSV Go ecosystem archive, including withdrawn and malicious-package source records; statement counts are not unique CVE counts","generation":"go-2375a4e597279abf92e8747e140fe8da9d421877cd49cae3ac69a2cb78469b2c","complete":true,"records":9779,"lastAttemptAt":"2026-10-26T00:46:57.4114497+00:00","lastSuccessAt":"2026-10-24T13:19:53.1346702+00:00","error":null,"lastVerifiedAt":"2026-10-26T00:46:57.4114497+00:00","snapshotPublishedAt":"2026-10-24T03:03:12+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null},{"source":"osv:NuGet","scope":"Complete OSV NuGet ecosystem archive, including GitHub Advisory Database records; NuGet version matching only","generation":"nuget-16ad89dfea13ab9e9b0108e63a759d63bd4559cc68b58491107d62ee35bbbaf2","complete":true,"records":1965,"lastAttemptAt":"2026-10-26T00:46:56.9270949+00:00","lastSuccessAt":"2026-10-23T16:01:26.4487605+00:00","error":null,"lastVerifiedAt":"2026-10-26T00:46:56.9270949+00:00","snapshotPublishedAt":"2026-10-21T12:18:07+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null},{"source":"osv:crates.io","scope":"Complete OSV crates.io ecosystem archive, including withdrawn and malicious-package source records; statement counts are not unique CVE counts","generation":"crates.io-7da67a15aa6e56a0e3081a7646dc74d537e6ef974afc593c2b1794ed01970648","complete":true,"records":2969,"lastAttemptAt":"2026-10-26T00:46:57.8104847+00:00","lastSuccessAt":"2026-10-24T13:19:59.1145547+00:00","error":null,"lastVerifiedAt":"2026-10-26T00:46:57.8104847+00:00","snapshotPublishedAt":"2026-10-24T08:47:51+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null},{"source":"osv:npm","scope":"Complete OSV npm ecosystem archive, including withdrawn and malicious-package source records; statement counts are not unique CVE counts","generation":"npm-11236ada05a0588e51df37636716526867f73fb127392c49680b6f8561496a99","complete":true,"records":230781,"lastAttemptAt":"2026-10-26T00:46:57.3095832+00:00","lastSuccessAt":"2026-10-25T22:04:07.173333+00:00","error":null,"lastVerifiedAt":"2026-10-26T00:46:57.3095832+00:00","snapshotPublishedAt":"2026-10-25T21:33:06+00:00","importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null}]}