CVE-2026-68312: cifs: fix cifsFileInfo leak on kmalloc failure in deferred close drain paths

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

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

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

cifs: fix cifsFileInfo leak on kmalloc failure in deferred close drain paths

In cifs_close_deferred_file(), cifs_close_all_deferred_files(), and
cifs_close_deferred_file_under_dentry(), when a pending deferred close
is cancelled via cancel_delayed_work(), the subsequent kmalloc_obj() to
add the file to the local processing list may fail under memory pressure.
The loop breaks immediately, but the cancelled work is no longer pending
(it would have called _cifsFileInfo_put()), and the cfile is never added
to file_head for processing.  The cifsFileInfo reference and the open
server handle both leak.

Fix by saving the cfile that failed allocation in a local variable,
breaking as before, and calling _cifsFileInfo_put() on it after
releasing the lock.  Any files later in the iteration are unaffected
since their deferred work is still pending and will fire normally.

The Linux kernel CVE team has assigned CVE-2026-68312 to this issue.


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

	Issue introduced in 5.15 with commit e3fc065682ebbbd15b0ce0036800f4acbf765d46 and fixed in 7.1.6 with commit 32390b3f06f26e366cfb27dbac4bc0196c321535
	Issue introduced in 5.15 with commit e3fc065682ebbbd15b0ce0036800f4acbf765d46 and fixed in 7.2-rc5 with commit c2f2e83e3bbc5483730fd4ee903182761f1ae50f

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-2026-68312
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/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/32390b3f06f26e366cfb27dbac4bc0196c321535
	https://git.kernel.org/stable/c/c2f2e83e3bbc5483730fd4ee903182761f1ae50f