From: Marco Elver <elver@google.com>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Alexander Potapenko <glider@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Christoph Lameter <cl@linux.com>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Mark Rutland <mark.rutland@arm.com>,
Pekka Enberg <penberg@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Andrey Konovalov <andreyknvl@google.com>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Andy Lutomirski <luto@kernel.org>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Eric Dumazet <edumazet@google.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Ingo Molnar <mingo@redhat.com>, Jann Horn <jannh@google.com>,
Jonathan Corbet <corbet@lwn.net>,
Kees Cook <keescook@chromium.org>,
Peter Zijlstra <peterz@infradead.org>, Qian Cai <cai@lca.pw>,
Thomas Gleixner <tglx@linutronix.de>,
Will Deacon <will@kernel.org>,
"the arch/x86 maintainers" <x86@kernel.org>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
kasan-dev <kasan-dev@googlegroups.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Linux-MM <linux-mm@kvack.org>
Subject: Re: [PATCH RFC 01/10] mm: add Kernel Electric-Fence infrastructure
Date: Thu, 10 Sep 2020 18:22:14 +0200 [thread overview]
Message-ID: <CANpmjNM53_yGwC1VFybzzZQ8f9wM=cjtmDdUYjWVct9CO1z6Ag@mail.gmail.com> (raw)
In-Reply-To: <CACT4Y+Z2Nay4mDjnHjooRa7u3ZXf72AFkF=EfkrZjCg9YEduMw@mail.gmail.com>
On Thu, 10 Sep 2020 at 17:48, Dmitry Vyukov <dvyukov@google.com> wrote:
>
> On Thu, Sep 10, 2020 at 5:06 PM Marco Elver <elver@google.com> wrote:
> > > On Mon, Sep 7, 2020 at 3:41 PM Marco Elver <elver@google.com> wrote:
> > > > +config KFENCE_NUM_OBJECTS
> > > > + int "Number of guarded objects available"
> > > > + default 255
> > > > + range 1 65535
> > > > + help
> > > > + The number of guarded objects available. For each KFENCE object, 2
> > > > + pages are required; with one containing the object and two adjacent
> > > > + ones used as guard pages.
> > >
> > > Hi Marco,
> > >
> > > Wonder if you tested build/boot with KFENCE_NUM_OBJECTS=65535? Can a
> > > compiler create such a large object?
> >
> > Indeed, I get a "ld: kernel image bigger than KERNEL_IMAGE_SIZE".
> > Let's lower it to something more reasonable.
> >
> > The main reason to have the limit is to constrain random configs and
> > avoid the inevitable error reports.
> >
> > > > +config KFENCE_FAULT_INJECTION
> > > > + int "Fault injection for stress testing"
> > > > + default 0
> > > > + depends on EXPERT
> > > > + help
> > > > + The inverse probability with which to randomly protect KFENCE object
> > > > + pages, resulting in spurious use-after-frees. The main purpose of
> > > > + this option is to stress-test KFENCE with concurrent error reports
> > > > + and allocations/frees. A value of 0 disables fault injection.
> > >
> > > I would name this differently. "FAULT_INJECTION" is already taken for
> > > a different thing, so it's a bit confusing.
> > > KFENCE_DEBUG_SOMETHING may be a better name.
> > > It would also be good to make it very clear in the short description
> > > that this is for testing of KFENCE itself. When I configure syzbot I
> > > routinely can't figure out if various DEBUG configs detect user
> > > errors, or enable additional unit tests, or something else.
> >
> > Makes sense, we'll change the name.
> >
> > > Maybe it should depend on DEBUG_KERNEL as well?
> >
> > EXPERT selects DEBUG_KERNEL, so depending on DEBUG_KERNEL doesn't make sense.
> >
> > > > +/*
> > > > + * Get the canary byte pattern for @addr. Use a pattern that varies based on the
> > > > + * lower 3 bits of the address, to detect memory corruptions with higher
> > > > + * probability, where similar constants are used.
> > > > + */
> > > > +#define KFENCE_CANARY_PATTERN(addr) ((u8)0xaa ^ (u8)((unsigned long)addr & 0x7))
> > >
> > > (addr) in macro body
> >
> > Done for v2.
> >
> > > > + seq_con_printf(seq,
> > > > + "kfence-#%zd [0x" PTR_FMT "-0x" PTR_FMT
> > >
> > > PTR_FMT is only used in this file, should it be declared in report.c?
> >
> > It's also used by the test.
> >
> > > Please post example reports somewhere. It's hard to figure out all
> > > details of the reporting/formatting.
> >
> > They can be seen in Documentation added later in the series (also
> > viewable here: https://github.com/google/kasan/blob/kfence/Documentation/dev-tools/kfence.rst)
>
>
> Looking at the first report. I got impression we are trying to skip
> __kfence frames, but this includes it:
>
> kfence-#17 [0xffffffffb672f000-0xffffffffb672f01f, size=32,
> cache=kmalloc-32] allocated in:
> __kfence_alloc+0x42d/0x4c0
> __kmalloc+0x133/0x200
>
> Is it working as intended?
We're not skipping them for the allocation/free stacks. We can skip
the kfence+kmalloc frame as well.
next prev parent reply other threads:[~2020-09-10 16:22 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-07 13:40 [PATCH RFC 00/10] KFENCE: A low-overhead sampling-based memory safety error detector Marco Elver
2020-09-07 13:40 ` [PATCH RFC 01/10] mm: add Kernel Electric-Fence infrastructure Marco Elver
2020-09-07 15:41 ` Jonathan Cameron
2020-09-07 16:38 ` Marco Elver
2020-09-10 14:57 ` Dmitry Vyukov
2020-09-10 15:06 ` Marco Elver
2020-09-10 15:48 ` Dmitry Vyukov
2020-09-10 16:22 ` Marco Elver [this message]
2020-09-10 15:42 ` Dmitry Vyukov
2020-09-10 16:19 ` Alexander Potapenko
2020-09-10 17:11 ` Dmitry Vyukov
2020-09-10 17:41 ` Marco Elver
2020-09-10 20:25 ` Paul E. McKenney
2020-09-15 13:57 ` SeongJae Park
2020-09-15 14:14 ` Marco Elver
2020-09-15 14:26 ` SeongJae Park
2020-09-07 13:40 ` [PATCH RFC 02/10] x86, kfence: enable KFENCE for x86 Marco Elver
2020-09-07 13:40 ` [PATCH RFC 03/10] arm64, kfence: enable KFENCE for ARM64 Marco Elver
2020-09-09 15:13 ` Marco Elver
2020-09-07 13:40 ` [PATCH RFC 04/10] mm, kfence: insert KFENCE hooks for SLAB Marco Elver
2020-09-11 7:17 ` Dmitry Vyukov
2020-09-11 12:24 ` Marco Elver
2020-09-11 13:03 ` Dmitry Vyukov
2020-09-07 13:40 ` [PATCH RFC 05/10] mm, kfence: insert KFENCE hooks for SLUB Marco Elver
2020-09-07 13:40 ` [PATCH RFC 06/10] kfence, kasan: make KFENCE compatible with KASAN Marco Elver
2020-09-11 7:04 ` Dmitry Vyukov
2020-09-11 13:00 ` Marco Elver
2020-09-07 13:40 ` [PATCH RFC 07/10] kfence, kmemleak: make KFENCE compatible with KMEMLEAK Marco Elver
2020-09-08 11:53 ` Catalin Marinas
2020-09-08 12:29 ` Alexander Potapenko
2020-09-07 13:40 ` [PATCH RFC 08/10] kfence, lockdep: make KFENCE compatible with lockdep Marco Elver
2020-09-07 13:40 ` [PATCH RFC 09/10] kfence, Documentation: add KFENCE documentation Marco Elver
2020-09-07 15:33 ` Andrey Konovalov
2020-09-07 16:33 ` Marco Elver
2020-09-07 17:55 ` Andrey Konovalov
2020-09-07 18:16 ` Marco Elver
2020-09-08 15:54 ` Dave Hansen
2020-09-08 16:14 ` Marco Elver
2020-09-11 7:14 ` Dmitry Vyukov
2020-09-11 7:46 ` Marco Elver
2020-09-07 13:40 ` [PATCH RFC 10/10] kfence: add test suite Marco Elver
2020-09-08 11:48 ` [PATCH RFC 00/10] KFENCE: A low-overhead sampling-based memory safety error detector Vlastimil Babka
2020-09-08 12:16 ` Alexander Potapenko
2020-09-08 14:40 ` Vlastimil Babka
2020-09-08 15:21 ` Marco Elver
2020-09-08 14:52 ` Dave Hansen
2020-09-08 15:31 ` Marco Elver
2020-09-08 15:36 ` Vlastimil Babka
2020-09-08 15:56 ` Marco Elver
2020-09-11 7:35 ` Dmitry Vyukov
2020-09-11 12:03 ` Marco Elver
2020-09-11 13:09 ` Dmitry Vyukov
2020-09-11 13:33 ` Marco Elver
2020-09-11 16:33 ` Marco Elver
2020-09-08 15:37 ` Dave Hansen
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