linux-kernel - Re: [PATCH v2 1/4][next] uapi: socket: Introduce struct sockaddr

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Message-ID: <20241031180145.01e14e38@kernel.org>
Date: Thu, 31 Oct 2024 18:01:45 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Andrew Lunn <andrew+netdev@...n.ch>, Johannes Berg
 <johannes@...solutions.net>, David Ahern <dsahern@...nel.org>, "David S.
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Paolo
 Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org, Kees Cook
 <kees@...nel.org>, Simon Horman <horms@...nel.org>
Subject: Re: [PATCH v2 1/4][next] uapi: socket: Introduce struct
 sockaddr_legacy

On Thu, 24 Oct 2024 15:11:24 -0600 Gustavo A. R. Silva wrote:
> + * This is the legacy form of `struct sockaddr`. The original `struct sockaddr`
> + * was modified in commit b5f0de6df6dce ("net: dev: Convert sa_data to flexible
> + * array in struct sockaddr") due to the fact that "One of the worst offenders
> + * of "fake flexible arrays" is struct sockaddr". This means that the original
> + * `char sa_data[14]` behaved as a flexible array at runtime, so a proper
> + * flexible-array member was introduced.

This isn't spelled out in the commit messages AFACT so let me ask..
Why aren't we reverting b5f0de6df6dce, then?
Feels like the best solution would be to have a separate type with
the flex array to clearly annotate users who treat it as such.
Is that not going to work?

My noob reading of b5f0de6df6dce is that it was a simpler workaround
for the previous problem, avoided adding a new type (and the conversion
churn). But now we are adding a type and another workaround on top.
Sorry if I'm misunderstanding. No question that the struct is a mess,
but I don't feel like this is helping the messiness...