CVE-2026-89632: smb: client: fix use-before-check of ReparseDataLength in reparse_buf_ptr()

CVE-2026-89632: smb: client: fix use-before-check of ReparseDataLength in reparse_buf_ptr()

[Greg Kroah-Hartman]

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

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

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

smb: client: fix use-before-check of ReparseDataLength in reparse_buf_ptr()

reparse_buf_ptr() reads buf->ReparseDataLength before checking that
count covers the full fixed header:

    buf = (struct reparse_data_buffer *)((u8 *)io + off);
    len = sizeof(*buf);                          /* 8 bytes */
    rdlen = le16_to_cpu(buf->ReparseDataLength); /* offset 4, 2 bytes */

    if (count < len || count < rdlen + len)      /* check comes after */

struct reparse_data_buffer has ReparseDataLength at offset 4.  If a
server returns OutputCount < 6, the read at offset 4-5 reaches past
the end of the received data.  The off+count bounds against iov_len
were already validated, but that does not protect against count being
smaller than sizeof(*buf).

Split the check: verify count >= sizeof(*buf) before reading
ReparseDataLength, then verify count covers the data region.

The Linux kernel CVE team has assigned CVE-2026-89632 to this issue.


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

	Issue introduced in 6.6.32 with commit a158bb66b1373866d9fd5997565a58a573085539 and fixed in 7.2.4 with commit 711cf71300d7992f450600df8864917d3538679f
	Issue introduced in 6.6.32 with commit a158bb66b1373866d9fd5997565a58a573085539 and fixed in 7.3-rc1 with commit 05f78e6cf34ea3a285053bd5999e08e8ac298bd5

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-2026-89632
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/smb2inode.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/711cf71300d7992f450600df8864917d3538679f
	https://git.kernel.org/stable/c/05f78e6cf34ea3a285053bd5999e08e8ac298bd5