linux-kernel - Re: [PATCH] exec: clarify reasoning for euid/egid reset

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Message-ID: <28638.1460481505@warthog.procyon.org.uk>
Date:	Tue, 12 Apr 2016 18:18:25 +0100
From:	David Howells <dhowells@...hat.com>
To:	Kees Cook <keescook@...omium.org>
Cc:	dhowells@...hat.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Serge Hallyn <serge.hallyn@...ntu.com>,
	Willy Tarreau <w@....eu>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] exec: clarify reasoning for euid/egid reset

Kees Cook <keescook@...omium.org> wrote:

> -	/* clear any previous set[ug]id data from a previous binary */
> +	/*
> +	 * Since this can be called multiple times (via prepare_binprm),
> +	 * we must clear any previous work done when setting set[ug]id
> +	 * bits from any earlier bprm->file uses (for example when run
> +	 * first for a script then for its interpreter).
> +	 */
>  	bprm->cred->euid = current_euid();
>  	bprm->cred->egid = current_egid();

I would further add that this is where we deal with setuid scripts.

David