CVE-2026-98686: smb: client: discard post-EOF pagecache when extending a file via zero range

CVE-2026-98686: smb: client: discard post-EOF pagecache when extending a file via zero range

[Greg Kroah-Hartman]

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

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

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

smb: client: discard post-EOF pagecache when extending a file via zero range

smb3_zero_range() removed the pagecache only for the range being zeroed,
so when it extends the file the folio straddling the old EOF - which may
hold data dirtied past EOF through an mmap - was never dropped and became
visible as file content once the file was extended.

Lower the discard boundary to the smaller of the zero-range offset and the
old EOF.

The Linux kernel CVE team has assigned CVE-2026-98686 to this issue.


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

	Issue introduced in 5.1 with commit 72c419d9b073628d3b5b0b2fc787b724f1a8c726 and fixed in 6.12.113 with commit 94949b6b2f2bf0dba2e8786aed0b08cc6bc3a183
	Issue introduced in 5.1 with commit 72c419d9b073628d3b5b0b2fc787b724f1a8c726 and fixed in 6.18.56 with commit b75dadb50a25eed525264bf6fea44fad94e7626f
	Issue introduced in 5.1 with commit 72c419d9b073628d3b5b0b2fc787b724f1a8c726 and fixed in 7.2.10 with commit 6a8279c98ad289b27c0bdb11adb3f0c0b7fd456d
	Issue introduced in 5.1 with commit 72c419d9b073628d3b5b0b2fc787b724f1a8c726 and fixed in 7.3-rc6 with commit da4fe97fb6c730d9c94a115c7bfa6f98e0d578d0

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-2026-98686
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/smb/client/smb2ops.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/94949b6b2f2bf0dba2e8786aed0b08cc6bc3a183
	https://git.kernel.org/stable/c/b75dadb50a25eed525264bf6fea44fad94e7626f
	https://git.kernel.org/stable/c/6a8279c98ad289b27c0bdb11adb3f0c0b7fd456d
	https://git.kernel.org/stable/c/da4fe97fb6c730d9c94a115c7bfa6f98e0d578d0