linux-cve-announce - CVE-2024-35841: net: tls, fix WARNIING in __sk_msg

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Message-ID: <2024051757-CVE-2024-35841-1f2e@gregkh>
Date: Fri, 17 May 2024 16:27:14 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-35841: net: tls, fix WARNIING in __sk_msg_free

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

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

net: tls, fix WARNIING in __sk_msg_free

A splice with MSG_SPLICE_PAGES will cause tls code to use the
tls_sw_sendmsg_splice path in the TLS sendmsg code to move the user
provided pages from the msg into the msg_pl. This will loop over the
msg until msg_pl is full, checked by sk_msg_full(msg_pl). The user
can also set the MORE flag to hint stack to delay sending until receiving
more pages and ideally a full buffer.

If the user adds more pages to the msg than can fit in the msg_pl
scatterlist (MAX_MSG_FRAGS) we should ignore the MORE flag and send
the buffer anyways.

What actually happens though is we abort the msg to msg_pl scatterlist
setup and then because we forget to set 'full record' indicating we
can no longer consume data without a send we fallthrough to the 'continue'
path which will check if msg_data_left(msg) has more bytes to send and
then attempts to fit them in the already full msg_pl. Then next
iteration of sender doing send will encounter a full msg_pl and throw
the warning in the syzbot report.

To fix simply check if we have a full_record in splice code path and
if not send the msg regardless of MORE flag.

The Linux kernel CVE team has assigned CVE-2024-35841 to this issue.

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

	Issue introduced in 6.5 with commit fe1e81d4f73b and fixed in 6.6.14 with commit 02e368eb1444
	Issue introduced in 6.5 with commit fe1e81d4f73b and fixed in 6.7.2 with commit 294e7ea85f34
	Issue introduced in 6.5 with commit fe1e81d4f73b and fixed in 6.8 with commit dc9dfc8dc629

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-2024-35841
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:
	net/tls/tls_sw.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/02e368eb1444a4af649b73cbe2edd51780511d86
	https://git.kernel.org/stable/c/294e7ea85f34748f04e5f3f9dba6f6b911d31aa8
	https://git.kernel.org/stable/c/dc9dfc8dc629e42f2234e3327b75324ffc752bc9