Vulnerability CVE-2023-52775
Published: 2024-05-21

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.

 References:
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
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