CVE-2026-64157: netfs: Fix partial invalidation of streaming-write folio

From: Greg Kroah-Hartman <[email protected]>

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

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

netfs: Fix partial invalidation of streaming-write folio

In netfs_invalidate_folio(), if the region of a partial invalidation
overlaps the front (but not all) of a dirty write cached in a streaming
write page (dirty, but not uptodate, with the dirty region tracked by a
netfs_folio struct), the function modifies the dirty region - but
incorrectly as it moves the region forward by setting the start to the
start, not the end, of the invalidation region.

Fix this by setting finfo->dirty_offset to the end of the invalidation
region (iend).

The Linux kernel CVE team has assigned CVE-2026-64157 to this issue.


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

	Issue introduced in 6.11 with commit cce6bfa6ca0e30af9927b0074c97fe6a92f28092 and fixed in 6.12.92 with commit f6b2569ae29b666fd15ff2848684c445ba442a39
	Issue introduced in 6.11 with commit cce6bfa6ca0e30af9927b0074c97fe6a92f28092 and fixed in 6.18.34 with commit 3d9601c029b934b5b6a10f99791467b10eb6b211
	Issue introduced in 6.11 with commit cce6bfa6ca0e30af9927b0074c97fe6a92f28092 and fixed in 7.0.11 with commit 6a3d27116be2c5fb9a03d5cf37c486ac517f3689
	Issue introduced in 6.11 with commit cce6bfa6ca0e30af9927b0074c97fe6a92f28092 and fixed in 7.1 with commit 6d91acc7fb85d33ea58fca9b964a32a453937f4b
	Issue introduced in 6.10.8 with commit e2814004138a541110d4b2dc254a8f619c2c4ce0

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-2026-64157
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/netfs/misc.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/f6b2569ae29b666fd15ff2848684c445ba442a39
	https://git.kernel.org/stable/c/3d9601c029b934b5b6a10f99791467b10eb6b211
	https://git.kernel.org/stable/c/6a3d27116be2c5fb9a03d5cf37c486ac517f3689
	https://git.kernel.org/stable/c/6d91acc7fb85d33ea58fca9b964a32a453937f4b