CVE-2026-97558: smb: client: fix cifsFileInfo reference leak in deferred close

CVE-2026-97558: smb: client: fix cifsFileInfo reference leak in deferred close

[Greg Kroah-Hartman]

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

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

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

smb: client: fix cifsFileInfo reference leak in deferred close

When cifs_close() defers a close, it hands the cifsFileInfo reference
of the closing struct file to the queued work. Each execution of
smb2_deferred_work_close() drops one such reference.

deferred_close_scheduled can be false while the work is pending: the
workqueue clears PENDING when the callback starts to run, before the
callback clears the flag under deferred_lock. A close in that
interval requeues the running work, and the callback then clears the
flag, leaving the requeued work pending with the flag down. A later
cifs_open() can reuse the handle and its cifs_close() reaches the
same branch: queue_delayed_work() fails because the work is still
pending, but cifs_close() returns without dropping the closing file's
reference. The cifsFileInfo count stays pinned and its tlink, dentry
and server handle are leaked.

Check the return value and hand off the reference only when work was
actually queued. Otherwise, use the shared _cifsFileInfo_put(), like
the mod_delayed_work() branch above: the pending execution already
owns its reference.

This issue was found by an in-house static analysis tool.

The Linux kernel CVE team has assigned CVE-2026-97558 to this issue.


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

	Issue introduced in 5.13 with commit c3f207ab29f793b8c942ce8067ed123f18d5b81b and fixed in 7.2.7 with commit ea93759d6c2789924f4e557aed5be532207715ea
	Issue introduced in 5.13 with commit c3f207ab29f793b8c942ce8067ed123f18d5b81b and fixed in 7.3-rc3 with commit 5520e89a5a4f834bced64cf2ac927001cc513a40

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-2026-97558
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/file.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/ea93759d6c2789924f4e557aed5be532207715ea
	https://git.kernel.org/stable/c/5520e89a5a4f834bced64cf2ac927001cc513a40