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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Kees Cook <kees@kernel.org>
Cc: Kees Cook <keescook@chromium.org>,
	linux-kernel@vger.kernel.org,
	 Alexey Dobriyan <adobriyan@gmail.com>,
	Josh Triplett <josh@joshtriplett.org>
Subject: Re: [GIT PULL] execve updates for v6.8-rc1
Date: Mon, 8 Jan 2024 17:53:51 -0800	[thread overview]
Message-ID: <CAHk-=wgnLA7Jhjiuz8W76PRyQheLCkNS__=D1onenqbhpiXsVQ@mail.gmail.com> (raw)
In-Reply-To: <D01C78AC-830C-4D73-9E9F-7FD38CEF2E82@kernel.org>

On Mon, 8 Jan 2024 at 17:48, Kees Cook <kees@kernel.org> wrote:
>
> This was exactly the feedback I had originally and wrote almost what you suggest:
>
> https://lore.kernel.org/lkml/202209161637.9EDAF6B18@keescook/
>
> But the perf testing of my proposed "look it up once" patch showed a
> net loss to the successful execs which no one could explain. In the
> end we went with the original proposal.

Basing things one one random benchmark which must clearly have some
very particular cache effects or something is not ok.

End result: I'm not taking a random "look up filename twice because we
can't understand what is going on".

Because I *guarantee* that we can trivially write another benchmark
that shows that looking up the pathname twice is worse.

                Linus

  reply	other threads:[~2024-01-09  1:54 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-01-08 18:35 [GIT PULL] execve updates for v6.8-rc1 Kees Cook
2024-01-09  0:19 ` Linus Torvalds
2024-01-09  0:30   ` Linus Torvalds
2024-01-09  0:46     ` Linus Torvalds
2024-01-09  1:48   ` Kees Cook
2024-01-09  1:53     ` Linus Torvalds [this message]
2024-01-09  3:28       ` Linus Torvalds
2024-01-09 18:57     ` Josh Triplett
2024-01-09 23:40       ` Linus Torvalds
2024-01-10  2:21         ` Josh Triplett
2024-01-10  3:54           ` Linus Torvalds
2024-01-11  9:47             ` Al Viro
2024-01-11 10:05               ` Al Viro
2024-01-11 17:42                 ` Linus Torvalds
2024-01-20 22:18                   ` Linus Torvalds
2024-01-21  8:05                     ` Kees Cook
2024-01-11 17:37               ` Linus Torvalds
2024-01-10 19:24           ` Kees Cook
2024-01-10 20:12             ` Linus Torvalds

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