CVE-2026-98539 (GCVE-0-2026-98539)

Vulnerability from cvelistv5 – Published: 2026-10-18 15:18 – Updated: 2026-10-19 09:21
VLAI
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: 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.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6651 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 82cae269cfa953032fbb8980a7d554d60fb00b17 , < 6fda7121cb6a8ea6fbd77d0f787f04b8e8b5358e (git)
Affected: 82cae269cfa953032fbb8980a7d554d60fb00b17 , < 37ec7353f4ac495b28284b0fcb0e53d21d1b3f3f (git)
Affected: 82cae269cfa953032fbb8980a7d554d60fb00b17 , < 1ae2a242c15b03470b1b16289298e597bbe3bb29 (git)
Affected: 82cae269cfa953032fbb8980a7d554d60fb00b17 , < 1abd643f3783ea8f8e273c18697ff0413aa92dc7 (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.15
Unaffected: 0 , < 5.15 (semver)
Unaffected: 6.12.112 , ≤ 6.12.* (semver)
Unaffected: 6.18.55 , ≤ 6.18.* (semver)
Unaffected: 7.2.9 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and murder syzbot\u0027s \"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\u0027s 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\u0027s 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\u0027t take it anymore so I went looking. Afaict, syzbot\u0027s\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(\u0026inode-\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) \u0026\u0026 ...):\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."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:21:22.671Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/37ec7353f4ac495b28284b0fcb0e53d21d1b3f3f"
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        {
          "url": "https://git.kernel.org/stable/c/1abd643f3783ea8f8e273c18697ff0413aa92dc7"
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      ],
      "title": "fs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and murder syzbot\u0027s \"WARNING in do_new_mount\" saga",
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    "cveId": "CVE-2026-98539",
    "datePublished": "2026-10-18T15:18:06.921Z",
    "dateReserved": "2026-09-25T10:25:14.356Z",
    "dateUpdated": "2026-10-19T09:21:22.671Z",
    "state": "PUBLISHED"
  },
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      "date": "2026-11-07",
      "epss": "0.00209",
      "percentile": "0.11125"
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      "cve": "CVE-2026-98539",
      "id": "msrc_CVE-2026-98539",
      "initial_release_date": "2026-10-20T01:06:59.000Z",
      "product_status:known_not_affected": "1",
      "product_status:under_investigation": "1",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "fs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and murder syzbot\u0027s \"WARNING in do_new_mount\" saga",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-98539.json",
      "version": "4"
    },
    "nvd": {
      "cve": {
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                "product": "Linux",
                "programFiles": [
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                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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                "vendor": "Linux",
                "versions": [
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and murder syzbot\u0027s \"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\u0027s 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\u0027s 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\u0027t take it anymore so I went looking. Afaict, syzbot\u0027s\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(\u0026inode-\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) \u0026\u0026 ...):\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."
          }
        ],
        "id": "CVE-2026-98539",
        "lastModified": "2026-10-19T10:19:09.680",
        "metrics": {},
        "published": "2026-10-18T16:17:05.733",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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            "url": "https://git.kernel.org/stable/c/6fda7121cb6a8ea6fbd77d0f787f04b8e8b5358e"
          }
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-11-07T11:07:06+00:00",
      "cve": "CVE-2026-98539",
      "id": "CVE-2026-98539",
      "initial_release_date": "2026-10-18T00:00:00+00:00",
      "product_status:known_not_affected": "203",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: fs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and murder syzbot\u0027s \"WARNING in do_new_mount\" saga",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-98539.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "not set",
      "current_release_date": "2026-10-18T23:45:26Z",
      "cve": "CVE-2026-98539",
      "id": "CVE-2026-98539",
      "initial_release_date": "2026-10-18T23:45:26Z",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-98539",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/2026/cve-2026-98539.json",
      "version": "2"
    }
  }
}



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