Subject: CVE-2024-49996: cifs: Fix buffer overflow when parsing NFS reparse points

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

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

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

cifs: Fix buffer overflow when parsing NFS reparse points

ReparseDataLength is sum of the InodeType size and DataBuffer size.
So to get DataBuffer size it is needed to subtract InodeType's size from
ReparseDataLength.

Function cifs_strndup_from_utf16() is currentlly accessing buf->DataBuffer
at position after the end of the buffer because it does not subtract
InodeType size from the length. Fix this problem and correctly subtract
variable len.

Member InodeType is present only when reparse buffer is large enough. Check
for ReparseDataLength before accessing InodeType to prevent another invalid
memory access.

Major and minor rdev values are present also only when reparse buffer is
large enough. Check for reparse buffer size before calling reparse_mkdev().

The Linux kernel CVE team has assigned CVE-2024-49996 to this issue.

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

	Issue introduced in 5.3 with commit d5ecebc4900d and fixed in 6.6.55 with commit c6db81c550ce
	Issue introduced in 5.3 with commit d5ecebc4900d and fixed in 6.10.14 with commit 803b3a39cb09
	Issue introduced in 5.3 with commit d5ecebc4900d and fixed in 6.11.3 with commit c173d47b69f0
	Issue introduced in 5.3 with commit d5ecebc4900d and fixed in 6.12-rc2 with commit e2a8910af016

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-2024-49996
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/reparse.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/c6db81c550cea0c73bd72ef55f579991e0e4ba07
	https://git.kernel.org/stable/c/803b3a39cb096d8718c0aebc03fd19f11c7dc919
	https://git.kernel.org/stable/c/c173d47b69f07cd7ca08efb4e458adbd4725d8e9
	https://git.kernel.org/stable/c/e2a8910af01653c1c268984855629d71fb81f404