In the Linux kernel, the following vulnerability has been resolved:
fs/ntfs3: fix deadlock in ni_read_folio_cmpr
Syzbot reported a task hung in ni_readpage_cmpr (now ni_read_folio_cmpr). This is caused by a lock inversion deadlock involving the inode mutex (ni_lock) and page locks.
Scenario:
- Task A enters ntfs_read_folio() for page X. It acquires ni_lock.
- Task A calls ni_read_folio_cmpr(), which attempts to lock all pages in
- Concurrently, Task B (e.g., via readahead) has locked page Y and
- Task B waits for ni_lock (held by A).
- Task A waits for page Y lock (held by B).
The fix is to restructure locking: do not take ni_lock in ntfs_read_folio(). Instead, acquire ni_lock inside ni_read_folio_cmpr() ONLY AFTER all required page locks for the frame have been successfully acquired. This restores the correct lock ordering (Page Lock -> ni_lock) consistent with VFS.
[almaz.alexandrovich@paragon-software.com: ni_readpage_cmpr was renamed to ni_read_folio_cmpr]