linux-kernel - Re: [GIT PULL] execve updates for v6.8-rc1

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Message-ID: <CAHk-=wgznerM-xs+x+krDfE7eVBiy_HOam35rbsFMMOwvYuEKQ@mail.gmail.com>
Date: Mon, 8 Jan 2024 16:19:45 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Kees Cook <keescook@...omium.org>
Cc: linux-kernel@...r.kernel.org, Alexey Dobriyan <adobriyan@...il.com>, 
	Josh Triplett <josh@...htriplett.org>
Subject: Re: [GIT PULL] execve updates for v6.8-rc1

On Mon, 8 Jan 2024 at 10:35, Kees Cook <keescook@...omium.org> wrote:
>
> Josh Triplett (1):
>       fs/exec.c: Add fast path for ENOENT on PATH search before allocating mm

No, we're not doing this.

If you want to open the file before the allocations, then dammit, do
exactly that.

Don't look up the path twice. Something (ENTIRELY UNTESTED) like this
patch that just moves the open from "bprm_execve()" to "alloc_bprm()".
It actually cleans up the odd BINPRM_FLAGS_PATH_INACCESSIBLE case too,
by setting it where it makes sense.

Anyway, I want to repeat: this patch is UNTESTED. It compiles for me.
But that is literally all the testing it has gotten apart from a
cursory "this patch looks sane".

There might be something seriously wrong with this patch, but it at
least makes sense, unlike that horror that will look up the filename
twice.

I bet whatever benchmark did the original was not using long filenames
with lots of components, or was only testing the ENOENT case.

                   Linus

View attachment "patch.diff" of type "text/x-patch" (4547 bytes)