{"id":"AZL-109007","summary":"CVE-2026-98539 affecting package kernel 6.6.157.1-1","details":"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(). 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-\u003ei_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.","modified":"2026-10-19T14:16:50.076692879Z","published":"2026-10-18T16:17:05Z","upstream":["CVE-2026-98539"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98539"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"6.6.157.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-109007.json"}}],"schema_version":"1.9.0"}