linux-kernel - Re: [PATCH 2/3] coredump: fix error handling for replace

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Message-ID: <20250414121156.GA28345@redhat.com>
Date: Mon, 14 Apr 2025 14:11:56 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Christian Brauner <brauner@...nel.org>
Cc: linux-fsdevel@...r.kernel.org, Luca Boccassi <luca.boccassi@...il.com>,
	Lennart Poettering <lennart@...ttering.net>,
	Daan De Meyer <daan.j.demeyer@...il.com>,
	Mike Yuan <me@...dnzj.com>,
	Zbigniew Jędrzejewski-Szmek <zbyszek@...waw.pl>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] coredump: fix error handling for replace_fd()

On 04/14, Christian Brauner wrote:
>
> The replace_fd() helper returns the file descriptor number on success
> and a negative error code on failure. The current error handling in
> umh_pipe_setup() only works because the file descriptor that is replaced
> is zero but that's pretty volatile. Explicitly check for a negative
> error code.

...

> @@ -515,6 +517,9 @@ static int umh_pipe_setup(struct subprocess_info *info, struct cred *new)
>  
>  	err = replace_fd(0, files[0], 0);
>  	fput(files[0]);
> +	if (err < 0)
> +		return err;
> +
>  	/* and disallow core files too */
>  	current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};

The patch looks trivial and correct, but if we do not want to rely on
the fact that replace_fd(fd => 0) return 0 on sucess, then this patch
should also do

	-	return err;
	+	return 0;

?

otherwise this cleanup looks "incomplete" to me.

Oleg.