CVE-2025-71309: fs/ntfs3: fix deadlock in ni_read_folio_cmpr

CVE-2025-71309: fs/ntfs3: fix deadlock in ni_read_folio_cmpr

[Greg Kroah-Hartman]

From: Greg Kroah-Hartman <gregkh@kernel.org>

Description
===========

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:
1. Task A enters ntfs_read_folio() for page X. It acquires ni_lock.
2. Task A calls ni_read_folio_cmpr(), which attempts to lock all pages in
   the compressed frame (including page Y).
3. Concurrently, Task B (e.g., via readahead) has locked page Y and
   calls ntfs_read_folio().
4. Task B waits for ni_lock (held by A).
5. Task A waits for page Y lock (held by B).
   -> DEADLOCK.

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]

The Linux kernel CVE team has assigned CVE-2025-71309 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.19 with commit f35590ee26f5722bfe12cdff14396c4c057a8f74 and fixed in 6.19.4 with commit cfe246b318106e1691bd6c9466c739e8559d25c2
	Issue introduced in 6.19 with commit f35590ee26f5722bfe12cdff14396c4c057a8f74 and fixed in 7.0 with commit e37a75bb866c29da954b51d0dd7670406246d9ee

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2025-71309
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	fs/ntfs3/frecord.c
	fs/ntfs3/inode.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/cfe246b318106e1691bd6c9466c739e8559d25c2
	https://git.kernel.org/stable/c/e37a75bb866c29da954b51d0dd7670406246d9ee