namespace: don't let a pseudo dentry become the root of a mount

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-98982
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-23 13:17:20 UTC
Updated2026-10-24 14:16:50 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: namespace: don't let a pseudo dentry become the root of a mount d_alloc_pseudo() hands out dentries for pipes, sockets and other files that are never anyone's child or parent. They carry DCACHE_NORCU and dentry_free() frees them right away because no lockless path walk can ever reach them. That holds as long as such a dentry isn't the root of a mount. But bind mounting /proc/self/fd/<fd> of such a file does exactly that. Most callers of alloc_file_pseudo() put their files on kernel-internal mounts and may_copy_tree() refuses those. bpf_token_create() doesn't. It places the token file on the bpffs mount the caller handed it and that mount is in the caller's mount namespace so the clone goes through: mount --bind /proc/self/fd/<token> <file> open_tree(tokfd, "", AT_EMPTY_PATH | OPEN_TREE_CLONE) + move_mount() __follow_mount_rcu() then loads ->mnt_root of that mount, reads d_seq and d_flags of the dentry and only then checks mount_lock. The dentry can be gone by then. The final mntput() of an unmounted parent unhooks a child that stayed attached to it under mount_lock alone. When the child's holder does the final put right after that the root is dput() and freed immediately while a walker that found the mount hashed still looks at it. Refuse to clone a mount with a DCACHE_NORCU dentry as its root. Nothing sensible can be done with a bind mount of a bpf token anyway.

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 35f96de04127d332a5c5e8a155d31f452f88c76d a256e31e0c54c4c37d2523aa52faabdcdd2ebc07 git Not specified
CNA Linux Linux affected 35f96de04127d332a5c5e8a155d31f452f88c76d 7e1c466011ba9e64d43075396badc03191bcee44 git Not specified
CNA Linux Linux affected 35f96de04127d332a5c5e8a155d31f452f88c76d 00287afa7cd989efdbf5822b7efac33cce7d489a git Not specified
CNA Linux Linux affected 35f96de04127d332a5c5e8a155d31f452f88c76d b138e16fb1e81376cea89f727dda7bfccd140de4 git Not specified
CNA Linux Linux affected 6.9 Not specified
CNA Linux Linux unaffected 6.9 semver Not specified
CNA Linux Linux unaffected 6.12.113 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.57 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.11 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/7e1c466011ba9e64d43075396badc03191bcee44 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/a256e31e0c54c4c37d2523aa52faabdcdd2ebc07 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b138e16fb1e81376cea89f727dda7bfccd140de4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/00287afa7cd989efdbf5822b7efac33cce7d489a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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