linux-kernel - Re: [PATCH] exec: move warning of null argv to be next to the relevant code

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Message-ID: <202411021304.1B1E0DBD@keescook>
Date: Sat, 2 Nov 2024 13:05:06 -0700
From: Kees Cook <kees@...nel.org>
To: nir@...htman.org
Cc: ebiederm@...ssion.com, viro@...iv.linux.org.uk, brauner@...nel.org,
	jack@...e.cz, linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] exec: move warning of null argv to be next to the
 relevant code

On Sat, Nov 02, 2024 at 02:01:22PM +0200, nir@...htman.org wrote:
> Problem: The warning is currently printed where it is detected that the
> arg count is zero but the action is only taken place later in the flow
> even though the warning is written as if the action is taken place in
> the time of print
> 
> This could be problematic since there could be a failure between the
> print and the code that takes action which would deem this warning
> misleading
> 
> Solution: Move the warning print after the action of adding an empty
> string as the first argument is successful
> 
> Signed-off-by: Nir Lichtman <nir@...htman.org>
> ---
> 
> Side note: I have noticed that currently the warn once variant is used
> for reporting this problem, which I guess is to reduce clutter that
> could go to dmesg, but wouldn't it be better to have this call the
> regular warn instead to better aid catching this type of bug?

We try to avoid having trivial ways to allow userspace to spam the
kernel dmesg log, so pr_warn_once() tends to be sufficient to catch this
relatively unlikely case.

-- 
Kees Cook