linux-kernel - Re: lib/test_overflow.c causes WARNING and tainted kernel

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Message-ID: <CAGXu5j+yRt_yf2CwvaZDUiEUMwTRRiWab6aeStxqodx9i+BR4g@mail.gmail.com>
Date:   Wed, 13 Mar 2019 19:53:09 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: lib/test_overflow.c causes WARNING and tainted kernel

Hi!

On Wed, Mar 13, 2019 at 2:29 PM Randy Dunlap <rdunlap@...radead.org> wrote:
>
> This is v5.0-11053-gebc551f2b8f9, MAR-12 around 4:00pm PT.
>
> In the first test_kmalloc() in test_overflow_allocation():
>
> [54375.073895] test_overflow: ok: (s64)(0 << 63) == 0
> [54375.074228] WARNING: CPU: 2 PID: 5462 at ../mm/page_alloc.c:4584 __alloc_pages_nodemask+0x33f/0x540
> [...]
> [54375.079236] ---[ end trace 754acb68d8d1a1cb ]---
> [54375.079313] test_overflow: kmalloc detected saturation

Yup! This is expected and operating as intended: it is exercising the
allocator's detection of insane allocation sizes. :)

If we want to make it less noisy, perhaps we could add a global flag
the allocators could check before doing their WARNs?

-Kees

-- 
Kees Cook