From: Andrey Ryabinin <aryabinin@virtuozzo.com> To: Dmitry Vyukov <dvyukov@google.com> Cc: Walter Wu <walter-zh.wu@mediatek.com>, Alexander Potapenko <glider@google.com>, Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Matthias Brugger <matthias.bgg@gmail.com>, Martin Schwidefsky <schwidefsky@de.ibm.com>, Arnd Bergmann <arnd@arndb.de>, Vasily Gorbik <gor@linux.ibm.com>, Andrey Konovalov <andreyknvl@google.com>, "Jason A . Donenfeld" <Jason@zx2c4.com>, Miles Chen <miles.chen@mediatek.com>, kasan-dev <kasan-dev@googlegroups.com>, LKML <linux-kernel@vger.kernel.org>, Linux-MM <linux-mm@kvack.org>, Linux ARM <linux-arm-kernel@lists.infradead.org>, linux-mediatek@lists.infradead.org, wsd_upstream <wsd_upstream@mediatek.com> Subject: Re: [PATCH v3] kasan: add memory corruption identification for software tag-based mode Date: Thu, 13 Jun 2019 18:50:25 +0300 [thread overview] Message-ID: <278bd641-7d74-b9ac-1549-1e630ef3d38c@virtuozzo.com> (raw) In-Reply-To: <CACT4Y+ZGEmGE2LFmRfPGgtUGwBqyL+s_CSp5DCpWGanTJCRcXw@mail.gmail.com> On 6/13/19 4:05 PM, Dmitry Vyukov wrote: > On Thu, Jun 13, 2019 at 2:27 PM Andrey Ryabinin <aryabinin@virtuozzo.com> wrote: >> On 6/13/19 11:13 AM, Walter Wu wrote: >>> This patch adds memory corruption identification at bug report for >>> software tag-based mode, the report show whether it is "use-after-free" >>> or "out-of-bound" error instead of "invalid-access" error.This will make >>> it easier for programmers to see the memory corruption problem. >>> >>> Now we extend the quarantine to support both generic and tag-based kasan. >>> For tag-based kasan, the quarantine stores only freed object information >>> to check if an object is freed recently. When tag-based kasan reports an >>> error, we can check if the tagged addr is in the quarantine and make a >>> good guess if the object is more like "use-after-free" or "out-of-bound". >>> >> >> >> We already have all the information and don't need the quarantine to make such guess. >> Basically if shadow of the first byte of object has the same tag as tag in pointer than it's out-of-bounds, >> otherwise it's use-after-free. >> >> In pseudo-code it's something like this: >> >> u8 object_tag = *(u8 *)kasan_mem_to_shadow(nearest_object(cacche, page, access_addr)); >> >> if (access_addr_tag == object_tag && object_tag != KASAN_TAG_INVALID) >> // out-of-bounds >> else >> // use-after-free > > But we don't have redzones in tag mode (intentionally), so unless I am > missing something we don't have the necessary info. Both cases look > the same -- we hit a different tag. We always have some redzone. We need a place to store 'struct kasan_alloc_meta', and sometimes also kasan_free_meta plus alignment to the next object. > There may only be a small trailer for kmalloc-allocated objects that > is painted with a different tag. I don't remember if we actually use a > different tag for the trailer. Since tag mode granularity is 16 bytes, > for smaller objects the trailer is impossible at all. > Smaller that 16-bytes objects have 16 bytes of kasan_alloc_meta. Redzones and freed objects always painted with KASAN_TAG_INVALID.
WARNING: multiple messages have this Message-ID (diff)
From: Andrey Ryabinin <aryabinin@virtuozzo.com> To: Dmitry Vyukov <dvyukov@google.com> Cc: wsd_upstream <wsd_upstream@mediatek.com>, Walter Wu <walter-zh.wu@mediatek.com>, Vasily Gorbik <gor@linux.ibm.com>, Arnd Bergmann <arnd@arndb.de>, Linux-MM <linux-mm@kvack.org>, Andrey Konovalov <andreyknvl@google.com>, "Jason A . Donenfeld" <Jason@zx2c4.com>, kasan-dev <kasan-dev@googlegroups.com>, LKML <linux-kernel@vger.kernel.org>, Pekka Enberg <penberg@kernel.org>, Martin Schwidefsky <schwidefsky@de.ibm.com>, Miles Chen <miles.chen@mediatek.com>, Alexander Potapenko <glider@google.com>, David Rientjes <rientjes@google.com>, Matthias Brugger <matthias.bgg@gmail.com>, linux-mediatek@lists.infradead.org, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Christoph Lameter <cl@linux.com>, Linux ARM <linux-arm-kernel@lists.infradead.org> Subject: Re: [PATCH v3] kasan: add memory corruption identification for software tag-based mode Date: Thu, 13 Jun 2019 18:50:25 +0300 [thread overview] Message-ID: <278bd641-7d74-b9ac-1549-1e630ef3d38c@virtuozzo.com> (raw) In-Reply-To: <CACT4Y+ZGEmGE2LFmRfPGgtUGwBqyL+s_CSp5DCpWGanTJCRcXw@mail.gmail.com> On 6/13/19 4:05 PM, Dmitry Vyukov wrote: > On Thu, Jun 13, 2019 at 2:27 PM Andrey Ryabinin <aryabinin@virtuozzo.com> wrote: >> On 6/13/19 11:13 AM, Walter Wu wrote: >>> This patch adds memory corruption identification at bug report for >>> software tag-based mode, the report show whether it is "use-after-free" >>> or "out-of-bound" error instead of "invalid-access" error.This will make >>> it easier for programmers to see the memory corruption problem. >>> >>> Now we extend the quarantine to support both generic and tag-based kasan. >>> For tag-based kasan, the quarantine stores only freed object information >>> to check if an object is freed recently. When tag-based kasan reports an >>> error, we can check if the tagged addr is in the quarantine and make a >>> good guess if the object is more like "use-after-free" or "out-of-bound". >>> >> >> >> We already have all the information and don't need the quarantine to make such guess. >> Basically if shadow of the first byte of object has the same tag as tag in pointer than it's out-of-bounds, >> otherwise it's use-after-free. >> >> In pseudo-code it's something like this: >> >> u8 object_tag = *(u8 *)kasan_mem_to_shadow(nearest_object(cacche, page, access_addr)); >> >> if (access_addr_tag == object_tag && object_tag != KASAN_TAG_INVALID) >> // out-of-bounds >> else >> // use-after-free > > But we don't have redzones in tag mode (intentionally), so unless I am > missing something we don't have the necessary info. Both cases look > the same -- we hit a different tag. We always have some redzone. We need a place to store 'struct kasan_alloc_meta', and sometimes also kasan_free_meta plus alignment to the next object. > There may only be a small trailer for kmalloc-allocated objects that > is painted with a different tag. I don't remember if we actually use a > different tag for the trailer. Since tag mode granularity is 16 bytes, > for smaller objects the trailer is impossible at all. > Smaller that 16-bytes objects have 16 bytes of kasan_alloc_meta. Redzones and freed objects always painted with KASAN_TAG_INVALID. _______________________________________________ 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:[~2019-06-13 15:50 UTC|newest] Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-06-13 8:13 [PATCH v3] kasan: add memory corruption identification for software tag-based mode Walter Wu 2019-06-13 8:13 ` Walter Wu 2019-06-13 8:13 ` Walter Wu 2019-06-13 12:27 ` Andrey Ryabinin 2019-06-13 12:27 ` Andrey Ryabinin 2019-06-13 12:27 ` Andrey Ryabinin 2019-06-13 13:05 ` Dmitry Vyukov 2019-06-13 13:05 ` Dmitry Vyukov 2019-06-13 13:05 ` Dmitry Vyukov 2019-06-13 13:05 ` Dmitry Vyukov 2019-06-13 15:50 ` Andrey Ryabinin [this message] 2019-06-13 15:50 ` Andrey Ryabinin 2019-06-13 17:46 ` Walter Wu 2019-06-13 17:46 ` Walter Wu 2019-06-13 17:46 ` Walter Wu 2019-06-14 2:32 ` Walter Wu 2019-06-14 2:32 ` Walter Wu 2019-06-14 2:32 ` Walter Wu 2019-06-17 4:00 ` Walter Wu 2019-06-17 4:00 ` Walter Wu 2019-06-17 4:00 ` Walter Wu 2019-06-17 11:57 ` Dmitry Vyukov 2019-06-17 11:57 ` Dmitry Vyukov 2019-06-17 11:57 ` Dmitry Vyukov 2019-06-17 12:32 ` Walter Wu 2019-06-17 12:32 ` Walter Wu 2019-06-17 12:32 ` Walter Wu 2019-07-01 9:56 ` Walter Wu 2019-07-01 9:56 ` Walter Wu 2019-07-01 9:56 ` Walter Wu 2019-07-05 13:34 ` Dmitry Vyukov 2019-07-05 13:34 ` Dmitry Vyukov 2019-07-05 13:34 ` Dmitry Vyukov 2019-07-08 16:33 ` Andrey Ryabinin 2019-07-08 16:33 ` Andrey Ryabinin 2019-07-09 2:53 ` Walter Wu 2019-07-09 2:53 ` Walter Wu 2019-07-09 2:53 ` Walter Wu 2019-07-10 18:24 ` Andrey Ryabinin 2019-07-10 18:24 ` Andrey Ryabinin 2019-07-11 10:06 ` Walter Wu 2019-07-11 10:06 ` Walter Wu 2019-07-11 10:06 ` Walter Wu 2019-07-12 10:52 ` Andrey Ryabinin 2019-07-12 10:52 ` Andrey Ryabinin 2019-07-15 3:06 ` Walter Wu 2019-07-15 3:06 ` Walter Wu 2019-07-15 3:06 ` Walter Wu 2019-07-18 16:11 ` Andrey Ryabinin 2019-07-18 16:11 ` Andrey Ryabinin 2019-07-22 9:52 ` Walter Wu 2019-07-22 9:52 ` Walter Wu 2019-07-22 9:52 ` Walter Wu 2019-07-26 12:00 ` Andrey Ryabinin 2019-07-26 12:00 ` Andrey Ryabinin 2019-07-26 12:28 ` Walter Wu 2019-07-26 12:28 ` Walter Wu 2019-07-26 12:28 ` Walter Wu 2019-07-26 12:52 ` Andrey Ryabinin 2019-07-26 12:52 ` Andrey Ryabinin 2019-07-26 13:19 ` Walter Wu 2019-07-26 13:19 ` Walter Wu 2019-07-26 13:19 ` Walter Wu 2019-07-31 17:04 ` Andrey Ryabinin 2019-07-31 17:04 ` Andrey Ryabinin 2019-08-02 3:04 ` Walter Wu 2019-08-02 3:04 ` Walter Wu 2019-08-02 3:04 ` Walter Wu
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