From: Jakub Kicinski <kuba@kernel.org>
To: Kees Cook <keescook@chromium.org>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>,
Subash Abhinov Kasiviswanathan <quic_subashab@quicinc.com>,
Sean Tranchetti <quic_stranche@quicinc.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Paolo Abeni <pabeni@redhat.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-hardening@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH][next] net: ethernet: rmnet: Replace zero-length array with DECLARE_FLEX_ARRAY() helper
Date: Tue, 27 Sep 2022 07:07:02 -0700 [thread overview]
Message-ID: <20220927070702.1c2da2b8@kernel.org> (raw)
In-Reply-To: <202209261920.3A2EA07D4@keescook>
On Mon, 26 Sep 2022 19:22:30 -0700 Kees Cook wrote:
> > Not directly related to this patch, but I just had to look at pahole
> > output for sk_buff and the struct_group() stuff makes is really painful
> > to read :/ Offsets for the members are relative to the "group" and they
> > are all repeated.
> >
> > Is there any chance you could fix that? Before we sprinkle more pixie
> > dust around, perhaps?
>
> Unfortunately I don't see a way around it until we can make changes to
> the C language spec, and that's measured in decades. :(
I think BPF folks have had some success adding C extensions, like
tagging. Some form of attribute would really look so much better than
this DECLARE_FLEX_ARRAY() macro indirection. Maybe it's just me :(
> Perhaps we could add some kind of heuristic to pahole to "hide" one of
> the internal struct_group() copies, and to hide the empty flexible-array
> wrapper structs? (pahole already can't tell the difference between a
> 0-length array and a flexible-array.) Would that be workable?
That'd be my knee-jerk fix, too. Or at least render the offsets for
the anonymous side of the union as absolute rather than relative.
prev parent reply other threads:[~2022-09-27 14:07 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-26 21:50 [PATCH][next] net: ethernet: rmnet: Replace zero-length array with DECLARE_FLEX_ARRAY() helper Gustavo A. R. Silva
2022-09-26 22:02 ` Kees Cook
2022-09-27 0:26 ` Jakub Kicinski
2022-09-27 2:22 ` Kees Cook
2022-09-27 14:07 ` Jakub Kicinski [this message]
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