From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-cve-announce@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@kernel.org>
Subject: CVE-2026-89640: cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0
Date: Fri, 11 Sep 2026 21:45:29 +0200 [thread overview]
Message-ID: <2026091141-CVE-2026-89640-ed71@gregkh> (raw)
From: Greg Kroah-Hartman <gregkh@kernel.org>
Description
===========
In the Linux kernel, the following vulnerability has been resolved:
cifs: fix loff_t underflow in cifs_remap_file_range() when len == 0
With len == 0 (clone to EOF), the effective length is computed as:
len = src_inode->i_size - off;
If off > i_size, this is a negative loff_t, corrupting the ByteCount
in the FSCTL_DUPLICATE_EXTENTS_TO_FILE request and inverting the range
in filemap_write_and_wait_range(). The existing off >= i_size check
fires only after the ioctl has already been sent.
Snapshot i_size_read() once for both the bounds check and the length
calculation, eliminating the TOCTOU and 32-bit torn-read risk. Reject
off > src_size with -EINVAL. Treat off == src_size as a no-op,
consistent with __generic_remap_file_range_prep().
The Linux kernel CVE team has assigned CVE-2026-89640 to this issue.
Affected and fixed versions
===========================
Issue introduced in 4.5 with commit 04b38d601239b4d9be641b412cf4b7456a041c67 and fixed in 6.12.109 with commit b098f5e5858797827666e6cd73033f52fc39b5f6
Issue introduced in 4.5 with commit 04b38d601239b4d9be641b412cf4b7456a041c67 and fixed in 6.18.50 with commit c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028
Issue introduced in 4.5 with commit 04b38d601239b4d9be641b412cf4b7456a041c67 and fixed in 7.2.4 with commit b057ca17b656345d04669cb87f2aff9b31d873db
Issue introduced in 4.5 with commit 04b38d601239b4d9be641b412cf4b7456a041c67 and fixed in 7.3-rc1 with commit 6c322f5cf7476ded7a9a20f7be72462065a03c68
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-2026-89640
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/cifsfs.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/b098f5e5858797827666e6cd73033f52fc39b5f6
https://git.kernel.org/stable/c/c2a0dcb5a7a1516aa6eb6d5cedca6a8e76527028
https://git.kernel.org/stable/c/b057ca17b656345d04669cb87f2aff9b31d873db
https://git.kernel.org/stable/c/6c322f5cf7476ded7a9a20f7be72462065a03c68
reply other threads:[~2026-09-11 20:00 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=2026091141-CVE-2026-89640-ed71@gregkh \
--to=gregkh@linuxfoundation.org \
--cc=cve@kernel.org \
--cc=gregkh@kernel.org \
--cc=linux-cve-announce@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.