AZL-85797

In the Linux kernel, the following vulnerability has been resolved:

ntfs3: fix circular locking dependency in rununpackex

Syzbot reported a circular locking dependency between wnd->rwlock (sbi->used.bitmap) and ni->file.runlock.

The deadlock scenario: 1. ntfsextendmft() takes ni->file.runlock then wnd->rwlock. 2. rununpackex() takes wnd->rwlock then tries to acquire ni->file.runlock inside ntfsrefreshzone().

This creates an AB-BA deadlock.

Fix this by using downreadtrylock() instead of downread() when acquiring runlock in rununpackex(). If the lock is contended, skip ntfsrefreshzone() - the MFT zone will be refreshed on the next MFT operation. This breaks the circular dependency since we never block waiting for runlock while holding wnd->rwlock.