From: Alexander Potapenko <glider@google.com> To: Jann Horn <jannh@google.com> Cc: Marco Elver <elver@google.com>, Christoph Lameter <cl@linux.com>, Andrew Morton <akpm@linux-foundation.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>, Catalin Marinas <catalin.marinas@arm.com>, Dave Hansen <dave.hansen@linux.intel.com>, David Rientjes <rientjes@google.com>, Dmitry Vyukov <dvyukov@google.com>, Eric Dumazet <edumazet@google.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Hillf Danton <hdanton@sina.com>, Ingo Molnar <mingo@redhat.com>, Jonathan Cameron <Jonathan.Cameron@huawei.com>, Jonathan Corbet <corbet@lwn.net>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Kees Cook <keescook@chromium.org>, Mark Rutland <mark.rutland@arm.com>, Pekka Enberg <penberg@kernel.org>, Peter Zijlstra <peterz@infradead.org>, SeongJae Park <sjpark@amazon.com>, Thomas Gleixner <tglx@linutronix.de>, Vlastimil Babka <vbabka@suse.cz>, Will Deacon <will@kernel.org>, "the arch/x86 maintainers" <x86@kernel.org>, "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>, kernel list <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 v4 05/11] mm, kfence: insert KFENCE hooks for SLUB Date: Mon, 5 Oct 2020 11:29:18 +0200 [thread overview] Message-ID: <CAG_fn=Wsxd+7COTzkqg-h82EzZgHq_bAM+u3u2rMh6VOmVQTdg@mail.gmail.com> (raw) In-Reply-To: <CAG48ez3X4dqXAEa7NFf6Vm3kq6Rk+z0scWqK6TV6jTo5+Pu+aA@mail.gmail.com> On Fri, Oct 2, 2020 at 9:07 AM Jann Horn <jannh@google.com> wrote: > > On Tue, Sep 29, 2020 at 3:38 PM Marco Elver <elver@google.com> wrote: > > Inserts KFENCE hooks into the SLUB allocator. > [...] > > diff --git a/mm/slub.c b/mm/slub.c > [...] > > @@ -3290,8 +3314,14 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size, > > c = this_cpu_ptr(s->cpu_slab); > > > > for (i = 0; i < size; i++) { > > - void *object = c->freelist; > > + void *object = kfence_alloc(s, s->object_size, flags); > > kfence_alloc() will invoke ->ctor() callbacks if the current slab has > them. Is it fine to invoke such callbacks from here, where we're in > the middle of a section that disables interrupts to protect against > concurrent freelist changes? If someone decides to be extra smart and > uses a kmem_cache with a ->ctor that can allocate memory from the same > kmem_cache, or something along those lines, this could lead to > corruption of the SLUB freelist. But I'm not sure whether that can > happen in practice. From cache_init_objs_debug() in mm/slab.c: /* * Constructors are not allowed to allocate memory from the same * cache which they are a constructor for. Otherwise, deadlock. * They must also be threaded. */ So, no, it is not allowed to allocate from the same cache in the constructor. > Still, it might be nicer if you could code this to behave like a > fastpath miss: Update c->tid, turn interrupts back on (___slab_alloc() > will also do that if it has to call into the page allocator), then let > kfence do the actual allocation in a more normal context, then turn > interrupts back off and go on. If that's not too complicated? > > Maybe Christoph Lameter has opinions on whether this is necessary... > it admittedly is fairly theoretical. > > > + if (unlikely(object)) { > > + p[i] = object; > > + continue; > > + } > > + > > + object = c->freelist; > > if (unlikely(!object)) { > > /* > > * We may have removed an object from c->freelist using -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Halimah DeLaine Prado Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg
WARNING: multiple messages have this Message-ID (diff)
From: Alexander Potapenko <glider@google.com> To: Jann Horn <jannh@google.com> Cc: Mark Rutland <mark.rutland@arm.com>, Hillf Danton <hdanton@sina.com>, "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>, Peter Zijlstra <peterz@infradead.org>, Catalin Marinas <catalin.marinas@arm.com>, Dave Hansen <dave.hansen@linux.intel.com>, Linux-MM <linux-mm@kvack.org>, Eric Dumazet <edumazet@google.com>, "H . Peter Anvin" <hpa@zytor.com>, Christoph Lameter <cl@linux.com>, Will Deacon <will@kernel.org>, SeongJae Park <sjpark@amazon.com>, Jonathan Corbet <corbet@lwn.net>, the arch/x86 maintainers <x86@kernel.org>, kasan-dev <kasan-dev@googlegroups.com>, Ingo Molnar <mingo@redhat.com>, Vlastimil Babka <vbabka@suse.cz>, David Rientjes <rientjes@google.com>, Andrey Ryabinin <aryabinin@virtuozzo.com>, Marco Elver <elver@google.com>, Kees Cook <keescook@chromium.org>, "Paul E . McKenney" <paulmck@kernel.org>, Andrey Konovalov <andreyknvl@google.com>, Borislav Petkov <bp@alien8.de>, Andy Lutomirski <luto@kernel.org>, Jonathan Cameron <Jonathan.Cameron@huawei.com>, Thomas Gleixner <tglx@linutronix.de>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Dmitry Vyukov <dvyukov@google.com>, Linux ARM <linux-arm-kernel@lists.infradead.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, kernel list <linux-kernel@vger.kernel.org>, Pekka Enberg <penberg@kernel.org>, Andrew Morton <akpm@linux-foundation.org> Subject: Re: [PATCH v4 05/11] mm, kfence: insert KFENCE hooks for SLUB Date: Mon, 5 Oct 2020 11:29:18 +0200 [thread overview] Message-ID: <CAG_fn=Wsxd+7COTzkqg-h82EzZgHq_bAM+u3u2rMh6VOmVQTdg@mail.gmail.com> (raw) In-Reply-To: <CAG48ez3X4dqXAEa7NFf6Vm3kq6Rk+z0scWqK6TV6jTo5+Pu+aA@mail.gmail.com> On Fri, Oct 2, 2020 at 9:07 AM Jann Horn <jannh@google.com> wrote: > > On Tue, Sep 29, 2020 at 3:38 PM Marco Elver <elver@google.com> wrote: > > Inserts KFENCE hooks into the SLUB allocator. > [...] > > diff --git a/mm/slub.c b/mm/slub.c > [...] > > @@ -3290,8 +3314,14 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size, > > c = this_cpu_ptr(s->cpu_slab); > > > > for (i = 0; i < size; i++) { > > - void *object = c->freelist; > > + void *object = kfence_alloc(s, s->object_size, flags); > > kfence_alloc() will invoke ->ctor() callbacks if the current slab has > them. Is it fine to invoke such callbacks from here, where we're in > the middle of a section that disables interrupts to protect against > concurrent freelist changes? If someone decides to be extra smart and > uses a kmem_cache with a ->ctor that can allocate memory from the same > kmem_cache, or something along those lines, this could lead to > corruption of the SLUB freelist. But I'm not sure whether that can > happen in practice. From cache_init_objs_debug() in mm/slab.c: /* * Constructors are not allowed to allocate memory from the same * cache which they are a constructor for. Otherwise, deadlock. * They must also be threaded. */ So, no, it is not allowed to allocate from the same cache in the constructor. > Still, it might be nicer if you could code this to behave like a > fastpath miss: Update c->tid, turn interrupts back on (___slab_alloc() > will also do that if it has to call into the page allocator), then let > kfence do the actual allocation in a more normal context, then turn > interrupts back off and go on. If that's not too complicated? > > Maybe Christoph Lameter has opinions on whether this is necessary... > it admittedly is fairly theoretical. > > > + if (unlikely(object)) { > > + p[i] = object; > > + continue; > > + } > > + > > + object = c->freelist; > > if (unlikely(!object)) { > > /* > > * We may have removed an object from c->freelist using -- Alexander Potapenko Software Engineer Google Germany GmbH Erika-Mann-Straße, 33 80636 München Geschäftsführer: Paul Manicle, Halimah DeLaine Prado Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-10-05 9:29 UTC|newest] Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-09-29 13:38 [PATCH v4 00/11] KFENCE: A low-overhead sampling-based memory safety error detector Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` [PATCH v4 01/11] mm: add Kernel Electric-Fence infrastructure Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-10-02 6:33 ` Jann Horn 2020-10-02 6:33 ` Jann Horn 2020-10-02 6:33 ` Jann Horn 2020-10-02 7:53 ` Jann Horn 2020-10-02 7:53 ` Jann Horn 2020-10-02 7:53 ` Jann Horn 2020-10-02 14:22 ` Dmitry Vyukov 2020-10-02 14:22 ` Dmitry Vyukov 2020-10-02 14:22 ` Dmitry Vyukov 2020-10-02 15:06 ` Mark Rutland 2020-10-02 15:06 ` Mark Rutland 2020-10-02 18:27 ` Jann Horn 2020-10-02 18:27 ` Jann Horn 2020-10-02 18:27 ` Jann Horn 2020-10-05 18:59 ` Marco Elver 2020-10-05 18:59 ` Marco Elver 2020-10-05 18:59 ` Marco Elver 2020-10-02 17:19 ` Marco Elver 2020-10-02 17:19 ` Marco Elver 2020-10-02 19:31 ` Jann Horn 2020-10-02 19:31 ` Jann Horn 2020-10-02 19:31 ` Jann Horn 2020-10-02 21:12 ` Marco Elver 2020-10-02 21:12 ` Marco Elver 2020-10-02 21:28 ` Marco Elver 2020-10-02 21:28 ` Marco Elver 2020-10-02 21:28 ` Marco Elver 2020-10-02 22:27 ` Jann Horn 2020-10-02 22:27 ` Jann Horn 2020-10-02 22:27 ` Jann Horn 2020-10-12 14:20 ` Marco Elver 2020-10-12 14:20 ` Marco Elver 2020-10-12 14:20 ` Marco Elver 2020-09-29 13:38 ` [PATCH v4 02/11] x86, kfence: enable KFENCE for x86 Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-10-02 5:45 ` Jann Horn 2020-10-02 5:45 ` Jann Horn 2020-10-02 5:45 ` Jann Horn 2020-10-07 13:08 ` Marco Elver 2020-10-07 13:08 ` Marco Elver 2020-10-07 13:08 ` Marco Elver 2020-10-07 14:14 ` Jann Horn 2020-10-07 14:14 ` Jann Horn 2020-10-07 14:14 ` Jann Horn 2020-10-07 14:41 ` Marco Elver 2020-10-07 14:41 ` Marco Elver 2020-10-07 14:41 ` Marco Elver 2020-10-09 17:40 ` Marco Elver 2020-10-09 17:40 ` Marco Elver 2020-10-02 6:08 ` Jann Horn 2020-10-02 6:08 ` Jann Horn 2020-10-02 6:08 ` Jann Horn 2020-09-29 13:38 ` [PATCH v4 03/11] arm64, kfence: enable KFENCE for ARM64 Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-10-02 6:47 ` Jann Horn 2020-10-02 6:47 ` Jann Horn 2020-10-02 6:47 ` Jann Horn 2020-10-02 14:18 ` Marco Elver 2020-10-02 14:18 ` Marco Elver 2020-10-02 14:18 ` Marco Elver 2020-10-02 16:10 ` Jann Horn 2020-10-02 16:10 ` Jann Horn 2020-10-02 16:10 ` Jann Horn 2020-09-29 13:38 ` [PATCH v4 04/11] mm, kfence: insert KFENCE hooks for SLAB Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` [PATCH v4 05/11] mm, kfence: insert KFENCE hooks for SLUB Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-10-02 7:07 ` Jann Horn 2020-10-02 7:07 ` Jann Horn 2020-10-02 7:07 ` Jann Horn 2020-10-05 9:29 ` Alexander Potapenko [this message] 2020-10-05 9:29 ` Alexander Potapenko 2020-10-05 9:29 ` Alexander Potapenko 2020-09-29 13:38 ` [PATCH v4 06/11] kfence, kasan: make KFENCE compatible with KASAN Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` [PATCH v4 07/11] kfence, kmemleak: make KFENCE compatible with KMEMLEAK Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` [PATCH v4 08/11] kfence, lockdep: make KFENCE compatible with lockdep Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` [PATCH v4 09/11] kfence, Documentation: add KFENCE documentation Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` [PATCH v4 10/11] kfence: add test suite Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` [PATCH v4 11/11] MAINTAINERS: Add entry for KFENCE Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 13:38 ` Marco Elver 2020-09-29 14:21 ` SeongJae Park 2020-09-29 14:21 ` SeongJae Park
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