From: David Laight <David.Laight@ACULAB.COM>
To: 'Christoph Hellwig' <hch@infradead.org>,
Kees Cook <keescook@chromium.org>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Al Viro <viro@zeniv.linux.org.uk>,
Luis Chamberlain <mcgrof@kernel.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
"linux-security-module@vger.kernel.org"
<linux-security-module@vger.kernel.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
James Morris <jmorris@namei.org>,
Kentaro Takeda <takedakn@nttdata.co.jp>,
Casey Schaufler <casey@schaufler-ca.com>,
"John Johansen" <john.johansen@canonical.com>
Subject: RE: [PATCH 7/7] exec: Implement kernel_execve
Date: Wed, 15 Jul 2020 14:55:50 +0000 [thread overview]
Message-ID: <d6d204c4427b49f6b24ac24bf1082fa4@AcuMS.aculab.com> (raw)
In-Reply-To: <20200715064248.GH32470@infradead.org>
From: Christoph Hellwig
> Sent: 15 July 2020 07:43
> Subject: Re: [PATCH 7/7] exec: Implement kernel_execve
>
> On Tue, Jul 14, 2020 at 02:49:23PM -0700, Kees Cook wrote:
> > On Tue, Jul 14, 2020 at 08:31:40AM -0500, Eric W. Biederman wrote:
> > > +static int count_strings_kernel(const char *const *argv)
> > > +{
> > > + int i;
> > > +
> > > + if (!argv)
> > > + return 0;
> > > +
> > > + for (i = 0; argv[i]; ++i) {
> > > + if (i >= MAX_ARG_STRINGS)
> > > + return -E2BIG;
> > > + if (fatal_signal_pending(current))
> > > + return -ERESTARTNOHAND;
> > > + cond_resched();
> > > + }
> > > + return i;
> > > +}
> >
> > I notice count() is only ever called with MAX_ARG_STRINGS. Perhaps
> > refactor that too? (And maybe rename it to count_strings_user()?)
Thinks....
If you setup env[] and argv[] on the new user stack early in exec processing
then you may not need any limits at all - except the size of the user stack.
Even the get_user() loop will hit an invalid address before the counter
wraps (provided it is unsigned long).
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2020-07-15 14:56 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-14 13:27 [PATCH 0/7] Implementing kernel_execve Eric W. Biederman
2020-07-14 13:28 ` [PATCH 1/7] exec: Remove unnecessary spaces from binfmts.h Eric W. Biederman
2020-07-14 21:38 ` Kees Cook
2020-07-15 6:28 ` Christoph Hellwig
2020-07-14 13:29 ` [PATCH 2/7] exec: Factor out alloc_bprm Eric W. Biederman
2020-07-14 21:38 ` Kees Cook
2020-07-15 6:30 ` Christoph Hellwig
2020-07-14 13:29 ` [PATCH 3/7] exec: Move initialization of bprm->filename into alloc_bprm Eric W. Biederman
2020-07-14 21:38 ` Kees Cook
2020-07-15 6:34 ` Christoph Hellwig
2020-07-14 13:30 ` [PATCH 4/7] exec: Move bprm_mm_init " Eric W. Biederman
2020-07-14 21:37 ` Kees Cook
2020-07-15 6:35 ` Christoph Hellwig
2020-07-14 13:30 ` [PATCH 5/7] exec: Factor bprm_execve out of do_execve_common Eric W. Biederman
2020-07-14 21:38 ` Kees Cook
2020-07-15 6:36 ` Christoph Hellwig
2020-07-14 13:31 ` [PATCH 6/7] exec: Factor bprm_stack_limits out of prepare_arg_pages Eric W. Biederman
2020-07-14 21:41 ` Kees Cook
2020-07-15 6:38 ` Christoph Hellwig
2020-07-14 13:31 ` [PATCH 7/7] exec: Implement kernel_execve Eric W. Biederman
2020-07-14 21:49 ` Kees Cook
2020-07-15 6:42 ` Christoph Hellwig
2020-07-15 14:55 ` David Laight [this message]
2020-07-15 15:09 ` Kees Cook
2020-07-15 16:46 ` David Laight
2020-07-15 15:00 ` Kees Cook
2020-07-15 18:20 ` Christoph Hellwig
2020-07-15 6:42 ` Christoph Hellwig
2020-07-15 18:23 ` Eric W. Biederman
2020-07-14 15:32 ` [PATCH 0/7] Implementing kernel_execve Linus Torvalds
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