linux-cve-announce - CVE-2024-41007: tcp: avoid too many retransmit packets

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Message-ID: <2024071513-CVE-2024-41007-777c@gregkh>
Date: Mon, 15 Jul 2024 10:48:14 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2024-41007: tcp: avoid too many retransmit packets

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

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

tcp: avoid too many retransmit packets

If a TCP socket is using TCP_USER_TIMEOUT, and the other peer
retracted its window to zero, tcp_retransmit_timer() can
retransmit a packet every two jiffies (2 ms for HZ=1000),
for about 4 minutes after TCP_USER_TIMEOUT has 'expired'.

The fix is to make sure tcp_rtx_probe0_timed_out() takes
icsk->icsk_user_timeout into account.

Before blamed commit, the socket would not timeout after
icsk->icsk_user_timeout, but would use standard exponential
backoff for the retransmits.

Also worth noting that before commit e89688e3e978 ("net: tcp:
fix unexcepted socket die when snd_wnd is 0"), the issue
would last 2 minutes instead of 4.

The Linux kernel CVE team has assigned CVE-2024-41007 to this issue.

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

	Issue introduced in 4.19 with commit b701a99e431d and fixed in 6.10 with commit 97a9063518f1

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-2024-41007
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/ipv4/tcp_timer.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/97a9063518f198ec0adb2ecb89789de342bb8283