{"id":"CVE-2026-98539","title":"fs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and murder syzbot's \"WARNING in do_new_mount\" saga","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nfs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and murder syzbot's \"WARNING in do_new_mount\" saga\n\nntfs_create_inode() creates a new inode via ntfs_new_inode(…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 82cae269cfa953032fbb8980a7d554d60fb00b17 < 6fda7121cb6a8ea6fbd77d0f787f04b8e8b5358e","Linux >= 82cae269cfa953032fbb8980a7d554d60fb00b17 < 37ec7353f4ac495b28284b0fcb0e53d21d1b3f3f","Linux >= 82cae269cfa953032fbb8980a7d554d60fb00b17 < 1ae2a242c15b03470b1b16289298e597bbe3bb29","Linux >= 82cae269cfa953032fbb8980a7d554d60fb00b17 < 1abd643f3783ea8f8e273c18697ff0413aa92dc7","Linux 5.15"],"published":"2026-10-18","updated":"2026-10-18","sourceUpdated":"2026-10-18T15:18:06.921Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98539","references":[{"url":"https://git.kernel.org/stable/c/6fda7121cb6a8ea6fbd77d0f787f04b8e8b5358e"},{"url":"https://git.kernel.org/stable/c/37ec7353f4ac495b28284b0fcb0e53d21d1b3f3f"},{"url":"https://git.kernel.org/stable/c/1ae2a242c15b03470b1b16289298e597bbe3bb29"},{"url":"https://git.kernel.org/stable/c/1abd643f3783ea8f8e273c18697ff0413aa92dc7"}],"tags":["cve.org"],"ingestedAt":"2026-10-18T15:45:12.277Z","slug":"CVE-2026-98539","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nfs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and murder syzbot's \"WARNING in do_new_mount\" saga\n\nntfs_create_inode() creates a new inode via ntfs_new_inode(). It hashes\nit with insert_inode_locked() and so it's marked as I_NEW until\nunlock_new_inode().\n\nntfs 3 calls d_instantiate() in between though... Since the dentry was\nalready hashed by the lookup before the create any path walk finds it\nwithout touching the parent's i_rwsem and so can lock the inode.\n\nIf the inode is a directory unlock_new_inode() calls\nlockdep_annotate_inode_mutex_key() and marks i_rwsem with the\ni_mutex_dir_key class.\n\nThat resets the count and the owner of a lock somebody else may already\nhold by now...\n\nsyzbot has been spamming us with the same godforsaken bug\n\n  \"WARNING in do_new_mount\"\n\nsince 2023. I can't take it anymore so I went looking. Afaict, syzbot's\nexecutor chdirs into a freshly mounted ntfs3 image, creates a\ndirectory and then mounts some pseudofs on it. Everytime the mkdir()\ntakes longer than syzbot waits mount() runs concurrently:\n\n  mkdir(\"./sys\")                        mount(NULL, \"./sys\", \"sysfs\")\n  ntfs_create_inode()\n    d_instantiate()\n                                        user_path_at() finds the dentry\n                                        do_lock_mount()\n                                          inode_lock(inode)\n                                          namespace_lock()\n    unlock_new_inode()\n      lockdep_annotate_inode_mutex_key()\n        init_rwsem(&inode->i_rwsem)\n                                        unlock_mount()\n                                          inode_unlock(inode)\n\nThe mount side then releases a lock that according to the rwsem nobody\nholds:\n\n  DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) && ...):\n  count = 0x0, magic = 0xffff888043a854e8, owner = 0x0,\n  curr 0xffff888000244880, list empty\n  WARNING: CPU: 0 PID: 5346 at kernel/locking/rwsem.c:1368 __up_write\n  Call Trace:\n   inode_unlock include/linux/fs.h:877 [inline]\n   unlock_mount fs/namespace.c:2892 [inline]\n   do_new_mount_fc fs/namespace.c:3828 [inline]\n   do_new_mount+0x777/0xa40 fs/namespace.c:3887\n\nOn PREEMPT_RT the same thing shows up as\n\n  DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current)\n  WARNING: kernel/locking/rtmutex_common.h:193 at rt_mutex_slowunlock\n\nThe up_write() underflows the reset count. A following inode_lock() on\nthat directory then never returns. A path walk into the new directory\nracing with the mkdir() corrupts the lock the same way via\ninode_lock_shared() in lookup_slow().\n\nSwitch to d_instantiate_new() and drop the trailing unlock_new_inode().\nAll error paths bail out before that point with I_NEW still set and\nkeep using discard_new_inode().\n\nMay we never see this fscking bug report again.\n\n## Affected\n\n- `Linux >= 82cae269cfa953032fbb8980a7d554d60fb00b17 < 6fda7121cb6a8ea6fbd77d0f787f04b8e8b5358e`\n- `Linux >= 82cae269cfa953032fbb8980a7d554d60fb00b17 < 37ec7353f4ac495b28284b0fcb0e53d21d1b3f3f`\n- `Linux >= 82cae269cfa953032fbb8980a7d554d60fb00b17 < 1ae2a242c15b03470b1b16289298e597bbe3bb29`\n- `Linux >= 82cae269cfa953032fbb8980a7d554d60fb00b17 < 1abd643f3783ea8f8e273c18697ff0413aa92dc7`\n- `Linux 5.15`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}