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Message-ID: <20171031023938.GE12341@eros>
Date: Tue, 31 Oct 2017 13:39:38 +1100
From: "Tobin C. Harding" <me@...in.cc>
To: Kees Cook <keescook@...omium.org>
Cc: kernel test robot <xiaolong.ye@...el.com>,
kernel-hardening@...ts.openwall.com,
"Jason A. Donenfeld" <Jason@...c4.com>,
Theodore Ts'o <tytso@....edu>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Tycho Andersen <tycho@...ker.com>,
"Roberts, William C" <william.c.roberts@...el.com>,
Tejun Heo <tj@...nel.org>,
Jordan Glover <Golden_Miller83@...tonmail.ch>,
Greg KH <gregkh@...uxfoundation.org>,
Petr Mladek <pmladek@...e.com>, Joe Perches <joe@...ches.com>,
Ian Campbell <ijc@...lion.org.uk>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <wilal.deacon@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Chris Fries <cfries@...gle.com>, Dave Weinstein <olorin@...gle.com>,
Daniel Micay <danielmicay@...il.com>,
Djalal Harouni <tixxdz@...il.com>,
LKML <linux-kernel@...r.kernel.org>, LKP <lkp@...org>
Subject: Re: [lkp-robot] [printk] 7f7c60e066: BUG:KASAN:slab-out-of-bounds
On Mon, Oct 30, 2017 at 05:14:59PM -0700, Kees Cook wrote:
> On Wed, Oct 25, 2017 at 9:22 AM, kernel test robot
> <xiaolong.ye@...el.com> wrote:
thanks for looking at this, I was at a loss as to what (if any) action I
needed to take.
> > FYI, we noticed the following commit (built with gcc-4.9):
> >
> > commit: 7f7c60e0663645e757e520245606fde9c6e326bb ("printk: hash addresses printed with %p")
> > url: https://github.com/0day-ci/linux/commits/Tobin-C-Harding/printk-hash-addresses-printed-with-p/20171024-231922
>
> It's not clear to me which of the various versions this test ran
> against, but it seems like the printf self-tests got very confused by
> the results:
>
> > [ 40.275423] test_printf: kvasprintf(..., "%p %p", ...) returned '3cf9adbe eff717bf', expected '0000000001234567 fffffffffedcba98'
> > [ 40.296739] test_printf: vsnprintf(buf, 256, "|%-*p|%*p|", ...) returned 19, expected 39
> > [ 40.322776] test_printf: vsnprintf(buf, 16, "|%-*p|%*p|", ...) returned 19, expected 39
> > [ 40.334834] test_printf: vsnprintf(buf, 0, "|%-*p|%*p|", ...) returned 19, expected 39
>
> I assume v10 will fix the width issues, but probably not the value tests...
Oh, so I need to update lib/test_printf.c to cover hashed %p.
> And it claims a use-after-free, too:
>
> > [ 39.757461] The buggy address belongs to the object at 22cb34bb
> > [ 39.757461] which belongs to the cache kmalloc-32 of size 32
> > [ 39.757461] The buggy address is located 0 bytes inside of
> > [ 39.757461] 32-byte region [22cb34bb, 24ac3a60)
>
> Which becomes rather unreadable, since the address got hashed. :P
So I think we need to patch mm/kasan/report to use %pK instead of %p.
I don't know what I should be doing about
[ 39.757461] BUG: KASAN: slab-out-of-bounds in __test+0xee/0x13f
Awesome, thanks,
Tobin.
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