fs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and murder syzbot's "WARNING in do_new_mount" saga

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-98539
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-18 16:17:05 UTC
Updated2026-10-18 16:17:05 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and murder syzbot's "WARNING in do_new_mount" saga ntfs_create_inode() creates a new inode via ntfs_new_inode(). It hashes it with insert_inode_locked() and so it's marked as I_NEW until unlock_new_inode(). ntfs 3 calls d_instantiate() in between though... Since the dentry was already hashed by the lookup before the create any path walk finds it without touching the parent's i_rwsem and so can lock the inode. If the inode is a directory unlock_new_inode() calls lockdep_annotate_inode_mutex_key() and marks i_rwsem with the i_mutex_dir_key class. That resets the count and the owner of a lock somebody else may already hold by now... syzbot has been spamming us with the same godforsaken bug "WARNING in do_new_mount" since 2023. I can't take it anymore so I went looking. Afaict, syzbot's executor chdirs into a freshly mounted ntfs3 image, creates a directory and then mounts some pseudofs on it. Everytime the mkdir() takes longer than syzbot waits mount() runs concurrently: mkdir("./sys") mount(NULL, "./sys", "sysfs") ntfs_create_inode() d_instantiate() user_path_at() finds the dentry do_lock_mount() inode_lock(inode) namespace_lock() unlock_new_inode() lockdep_annotate_inode_mutex_key() init_rwsem(&inode->i_rwsem) unlock_mount() inode_unlock(inode) The mount side then releases a lock that according to the rwsem nobody holds: DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) && ...): count = 0x0, magic = 0xffff888043a854e8, owner = 0x0, curr 0xffff888000244880, list empty WARNING: CPU: 0 PID: 5346 at kernel/locking/rwsem.c:1368 __up_write Call Trace: inode_unlock include/linux/fs.h:877 [inline] unlock_mount fs/namespace.c:2892 [inline] do_new_mount_fc fs/namespace.c:3828 [inline] do_new_mount+0x777/0xa40 fs/namespace.c:3887 On PREEMPT_RT the same thing shows up as DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current) WARNING: kernel/locking/rtmutex_common.h:193 at rt_mutex_slowunlock The up_write() underflows the reset count. A following inode_lock() on that directory then never returns. A path walk into the new directory racing with the mkdir() corrupts the lock the same way via inode_lock_shared() in lookup_slow(). Switch to d_instantiate_new() and drop the trailing unlock_new_inode(). All error paths bail out before that point with I_NEW still set and keep using discard_new_inode(). May we never see this fscking bug report again.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 82cae269cfa953032fbb8980a7d554d60fb00b17 6fda7121cb6a8ea6fbd77d0f787f04b8e8b5358e git Not specified
CNA Linux Linux affected 82cae269cfa953032fbb8980a7d554d60fb00b17 37ec7353f4ac495b28284b0fcb0e53d21d1b3f3f git Not specified
CNA Linux Linux affected 82cae269cfa953032fbb8980a7d554d60fb00b17 1ae2a242c15b03470b1b16289298e597bbe3bb29 git Not specified
CNA Linux Linux affected 82cae269cfa953032fbb8980a7d554d60fb00b17 1abd643f3783ea8f8e273c18697ff0413aa92dc7 git Not specified
CNA Linux Linux affected 5.15 Not specified
CNA Linux Linux unaffected 5.15 semver Not specified
CNA Linux Linux unaffected 6.12.112 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.55 6.18.* semver Not specified
CNA Linux Linux unaffected 7.2.9 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/1ae2a242c15b03470b1b16289298e597bbe3bb29 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/6fda7121cb6a8ea6fbd77d0f787f04b8e8b5358e 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1abd643f3783ea8f8e273c18697ff0413aa92dc7 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/37ec7353f4ac495b28284b0fcb0e53d21d1b3f3f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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