CVE-2026-64160: netfs: Fix potential for tearing in ->remote_i_size and ->zero_point

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

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

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

netfs: Fix potential for tearing in ->remote_i_size and ->zero_point

Fix potential tearing in using ->remote_i_size and ->zero_point by copying
i_size_read() and i_size_write() and using the same seqcount as for i_size.

We need to make sure that netfslib and the filesystems that use it always
hold i_lock whilst updating any of the sizes to prevent i_size_seqcount
from getting corrupted.

The Linux kernel CVE team has assigned CVE-2026-64160 to this issue.


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

	Issue introduced in 5.18 with commit 4058f742105ecfcbdf99e1139e6c1f74fb8e6db9 and fixed in 7.0.11 with commit 55970f238d495517edc961d55c44c772594d0969
	Issue introduced in 5.18 with commit 4058f742105ecfcbdf99e1139e6c1f74fb8e6db9 and fixed in 7.1 with commit 2c8f4742bb76117d735f92a3932d85239b16c494

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-2026-64160
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/9p/v9fs_vfs.h
	fs/9p/vfs_inode.c
	fs/9p/vfs_inode_dotl.c
	fs/afs/file.c
	fs/afs/inode.c
	fs/afs/internal.h
	fs/afs/write.c
	fs/netfs/buffered_read.c
	fs/netfs/buffered_write.c
	fs/netfs/direct_write.c
	fs/netfs/misc.c
	fs/netfs/write_collect.c
	fs/smb/client/cifsfs.c
	fs/smb/client/cifssmb.c
	fs/smb/client/file.c
	fs/smb/client/inode.c
	fs/smb/client/readdir.c
	fs/smb/client/smb2ops.c
	fs/smb/client/smb2pdu.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/55970f238d495517edc961d55c44c772594d0969
	https://git.kernel.org/stable/c/2c8f4742bb76117d735f92a3932d85239b16c494