Re: [PATCH] amd64: Fix csum_partial_copy_generic()

[Al Viro]

On Wed, Oct 18, 2023 at 06:18:05AM +0000, gus Gusenleitner Klaus wrote:
> The checksum calculation is wrong in case of an source buffer
> containing zero bytes only. The expected return value is 0, the
> actual return value is 0xfffffff.

Expected where?  The actual checksum is defined modulo 0xffff, so
0 and 0xffffffff represent the same final value.

The only twist is that in some situations we internally use 0 for
"not calculated yet".

> This problem occurs when a ICMP echo reply is sent that has set
> zero identifier, sequence number and data.

What problem?  Could you please either point to specific RFC or
show that packets are rejected by some existing system, or...?