Subject: CVE-2023-52775: net/smc: avoid data corruption caused by decline

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

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

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

net/smc: avoid data corruption caused by decline

We found a data corruption issue during testing of SMC-R on Redis
applications.

The benchmark has a low probability of reporting a strange error as
shown below.

"Error: Protocol error, got "\xe2" as reply type byte"

Finally, we found that the retrieved error data was as follows:

0xE2 0xD4 0xC3 0xD9 0x04 0x00 0x2C 0x20 0xA6 0x56 0x00 0x16 0x3E 0x0C
0xCB 0x04 0x02 0x01 0x00 0x00 0x20 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0xE2

It is quite obvious that this is a SMC DECLINE message, which means that
the applications received SMC protocol message.
We found that this was caused by the following situations:

client                  server
        ¦  clc proposal
        ------------->
        ¦  clc accept
        <-------------
        ¦  clc confirm
        ------------->
wait llc confirm
			send llc confirm
        ¦failed llc confirm
        ¦   x------
(after 2s)timeout
                        wait llc confirm rsp

wait decline

(after 1s) timeout
                        (after 2s) timeout
        ¦   decline
        -------------->
        ¦   decline
        <--------------

As a result, a decline message was sent in the implementation, and this
message was read from TCP by the already-fallback connection.

This patch double the client timeout as 2x of the server value,
With this simple change, the Decline messages should never cross or
collide (during Confirm link timeout).

This issue requires an immediate solution, since the protocol updates
involve a more long-term solution.

The Linux kernel CVE team has assigned CVE-2023-52775 to this issue.

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

	Issue introduced in 5.8 with commit 0fb0b02bd6fd and fixed in 5.10.203 with commit 5ada292b5c50
	Issue introduced in 5.8 with commit 0fb0b02bd6fd and fixed in 5.15.141 with commit 90072af9efe8
	Issue introduced in 5.8 with commit 0fb0b02bd6fd and fixed in 6.1.65 with commit 94a0ae698b4d
	Issue introduced in 5.8 with commit 0fb0b02bd6fd and fixed in 6.6.4 with commit 7234d2b5dffa
	Issue introduced in 5.8 with commit 0fb0b02bd6fd and fixed in 6.7 with commit e6d71b437abc

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-2023-52775
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/smc/af_smc.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/5ada292b5c504720a0acef8cae9acc62a694d19c
	https://git.kernel.org/stable/c/90072af9efe8c7bd7d086709014ddd44cebd5e7c
	https://git.kernel.org/stable/c/94a0ae698b4d5d5bb598e23228002a1491c50add
	https://git.kernel.org/stable/c/7234d2b5dffa5af77fd4e0deaebab509e130c6b1
	https://git.kernel.org/stable/c/e6d71b437abc2f249e3b6a1ae1a7228e09c6e563