linux-kernel - Re: [patch 0/3] no MAX_ARG

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <65dd6fd50706141358i39bba32aq139766c8a1a3de2b@mail.gmail.com>
Date:	Thu, 14 Jun 2007 13:58:58 -0700
From:	"Ollie Wild" <aaw@...gle.com>
To:	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>
Cc:	"Luck, Tony" <tony.luck@...el.com>, linux-kernel@...r.kernel.org,
	parisc-linux@...ts.parisc-linux.org, linux-mm@...ck.org,
	linux-arch@...r.kernel.org, "Andrew Morton" <akpm@...l.org>,
	"Ingo Molnar" <mingo@...e.hu>, "Andi Kleen" <ak@...e.de>
Subject: Re: [patch 0/3] no MAX_ARG_PAGES -v2

> @@ -1385,6 +1401,10 @@ int do_execve(char * filename,
>                 goto out;
>         bprm->argv_len = env_p - bprm->p;
>
> +       retval = expand_arg_vma(bprm);
> +       if (retval < 0)
> +               goto out;
> +
>         retval = search_binary_handler(bprm,regs);
>         if (retval >= 0) {
>                 /* execve success */

At this point bprm->argc hasn't been finalized yet.  For example, the
script binfmt reads the script header and adds additional arguments.
The flush_old_exec() function is a better place to call this.

I'm not 100% sure this is the right way to handle this, though.  The
problem isn't as simple as ensuring the stack doesn't overflow during
argument allocation.  We also need to ensure the program has
sufficient stack space to run subsequently.  Otherwise, the observable
behavior is identical.  Since we can't realistically predict
acceptable stack availability requirements, some amount of uncertainty
is always going to exist.  A good heuristic, though, might be to limit
argument size to a percentage (say 25%) of maximum stack size and
validate this inside copy_strings().

Ollie
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/