linux-kernel - Re: [PATCH] exec: separate MM_ANONPAGES and RLIMIT

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <20181126122307.GA1660@redhat.com>
Date:   Mon, 26 Nov 2018 13:23:07 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Ben Woodard <woodard@...hat.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>,
        Michal Hocko <mhocko@...e.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] exec: separate MM_ANONPAGES and RLIMIT_STACK accounting

Hi Guenter,

On 11/23, Guenter Roeck wrote:
>
> On Mon, Nov 12, 2018 at 05:09:10PM +0100, Oleg Nesterov wrote:
> > get_arg_page() checks bprm->rlim_stack.rlim_cur and re-calculates the
> > "extra" size for argv/envp pointers every time, this is a bit ugly and
> > even not strictly correct: acct_arg_size() must not account this size.
> >
> > Remove all the rlimit code in get_arg_page(). Instead, add bprm->argmin
> > calculated once at the start of __do_execve_file() and change copy_strings
> > to check bprm->p >= bprm->argmin.
> >
> > The patch adds the new helper, prepare_arg_pages() which initializes
> > bprm->argc/envc and bprm->argmin.
> >
> > Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> > Acked-by: Kees Cook <keescook@...omium.org>
>
> This patch results in various qemu boot failures in -next. Bisect logs
> are attached. It looks like all nommu boots are failing.
                                  ^^^^^

Ah, thanks.

Yes, I forgot about the !CONFIG_MMU version of get_arg_page() which doesn't
check RLIMIT_STACK at all.

I'll send the trivial fix. Meanwile, could you test the patch below? to ensure
this is the only problem.

Oleg.

--- a/fs/exec.c
+++ b/fs/exec.c
@@ -526,8 +526,10 @@ static int copy_strings(int argc, struct user_arg_ptr argv,
 		pos = bprm->p;
 		str += len;
 		bprm->p -= len;
+#ifdef CONFIG_MMU
 		if (bprm->p < bprm->argmin)
 			goto out;
+#endif
 
 		while (len > 0) {
 			int offset, bytes_to_copy;