CVE-2026-64216: netfs: Fix potential UAF in netfs_unlock_abandoned_read_pages()

CVE-2026-64216: netfs: Fix potential UAF in netfs_unlock_abandoned_read_pages()

[Greg Kroah-Hartman]

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

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

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

netfs: Fix potential UAF in netfs_unlock_abandoned_read_pages()

netfs_unlock_abandoned_read_pages(rreq) accesses the index of the folios it
is wanting to unlock and compares that to rreq->no_unlock_folio so that it
doesn't unlock a folio being read for netfs_perform_write() or
netfs_write_begin().

However, given that netfs_unlock_abandoned_read_pages() is called _after_
NETFS_RREQ_IN_PROGRESS is cleared, the one folio that it's not allowed to
dereference is the one specified by ->no_unlock_folio as ownership
immediately reverts to the caller.

Fix this by storing the folio pointer instead and using that rather than
the index.  Also fix netfs_unlock_read_folio() where the same applies.

The Linux kernel CVE team has assigned CVE-2026-64216 to this issue.


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

	Issue introduced in 6.12 with commit ee4cdf7ba857a894ad1650d6ab77669cbbfa329e and fixed in 6.18.34 with commit 6080fa3ecfbb4448a3b47368629534c09b6ec750
	Issue introduced in 6.12 with commit ee4cdf7ba857a894ad1650d6ab77669cbbfa329e and fixed in 7.0.11 with commit 3866d015f33aeedf81338dd99154703bef33faef
	Issue introduced in 6.12 with commit ee4cdf7ba857a894ad1650d6ab77669cbbfa329e and fixed in 7.1 with commit dbe556972100fabb8e5a1b3d2163831ff07b1e8e

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-2026-64216
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/buffered_read.c
	fs/netfs/read_collect.c
	fs/netfs/read_retry.c
	include/linux/netfs.h


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/6080fa3ecfbb4448a3b47368629534c09b6ec750
	https://git.kernel.org/stable/c/3866d015f33aeedf81338dd99154703bef33faef
	https://git.kernel.org/stable/c/dbe556972100fabb8e5a1b3d2163831ff07b1e8e