From: Alexander Potapenko <glider@google.com> To: Marco Elver <elver@google.com> Cc: Vegard Nossum <vegard.nossum@oracle.com>, Dmitry Vyukov <dvyukov@google.com>, Linux Memory Management List <linux-mm@kvack.org>, Al Viro <viro@zeniv.linux.org.uk>, Andreas Dilger <adilger.kernel@dilger.ca>, Andrew Morton <akpm@linux-foundation.org>, Andrey Konovalov <andreyknvl@google.com>, Andrey Ryabinin <aryabinin@virtuozzo.com>, Andy Lutomirski <luto@kernel.org>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, Arnd Bergmann <arnd@arndb.de>, Christoph Hellwig <hch@infradead.org>, Christoph Hellwig <hch@lst.de>, "Darrick J. Wong" <darrick.wong@oracle.com>, "David S. Miller" <davem@davemloft.net>, Dmitry Torokhov <dmitry.torokhov@gmail.com>, Eric Biggers <ebiggers@google.com>, Eric Dumazet <edumazet@google.com>, Eric Van Hensbergen <ericvh@gmail.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Harry Wentland <harry.wentland@amd.com>, Herbert Xu <herbert@gondor.apana.org.au>, Ilya Leoshkevich <iii@linux.ibm.com>, Ingo Molnar <mingo@elte.hu>, Jason Wang <jasowang@redhat.com>, Jens Axboe <axboe@kernel.dk>, Marek Szyprowski <m.szyprowski@samsung.com>, Mark Rutland <mark.rutland@arm.com>, "Martin K. Petersen" <martin.petersen@oracle.com>, Martin Schwidefsky <schwidefsky@de.ibm.com>, Matthew Wilcox <willy@infradead.org>, "Michael S. Tsirkin" <mst@redhat.com>, Michal Simek <monstr@monstr.eu>, Petr Mladek <pmladek@suse.com>, Qian Cai <cai@lca.pw>, Randy Dunlap <rdunlap@infradead.org>, Robin Murphy <robin.murphy@arm.com>, Sergey Senozhatsky <sergey.senozhatsky@gmail.com>, Steven Rostedt <rostedt@goodmis.org>, Takashi Iwai <tiwai@suse.com>, "Theodore Ts'o" <tytso@mit.edu>, Thomas Gleixner <tglx@linutronix.de>, Vasily Gorbik <gor@linux.ibm.com>, Wolfram Sang <wsa@the-dreams.de> Subject: Re: [PATCH RFC v3 31/36] kmsan: disable strscpy() optimization under KMSAN Date: Tue, 3 Dec 2019 12:19:16 +0100 Message-ID: <CAG_fn=Xgv5oQY65RiCbw2cN7gNt41n1HbJUFjwD3N5nuP-yxdQ@mail.gmail.com> (raw) In-Reply-To: <CAG_fn=WgeCY0d2tPmfCL9G7T=KJVEH5WmTp0t_GVq7Z8STnb0Q@mail.gmail.com> On Mon, Dec 2, 2019 at 5:23 PM Alexander Potapenko <glider@google.com> wrote: > > On Mon, Dec 2, 2019 at 4:51 PM Marco Elver <elver@google.com> wrote: > > > > On Fri, 22 Nov 2019 at 12:28, <glider@google.com> wrote: > > > > > > Disable the efficient 8-byte reading under KMSAN to avoid false positives. > > > > > > Signed-off-by: Alexander Potapenko <glider@google.com> > > > To: Alexander Potapenko <glider@google.com> > > > Cc: Vegard Nossum <vegard.nossum@oracle.com> > > > Cc: Dmitry Vyukov <dvyukov@google.com> > > > Cc: linux-mm@kvack.org > > > > > > --- > > > > > > Change-Id: I25d1acf5c3df6eff85894cd94f5ddbe93308271c > > > --- > > > lib/string.c | 5 ++++- > > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > > > diff --git a/lib/string.c b/lib/string.c > > > index 08ec58cc673b..15efdc51bda6 100644 > > > --- a/lib/string.c > > > +++ b/lib/string.c > > > @@ -186,7 +186,10 @@ ssize_t strscpy(char *dest, const char *src, size_t count) > > > if (count == 0 || WARN_ON_ONCE(count > INT_MAX)) > > > return -E2BIG; > > > > > > -#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS > > > +/** > > > > Why a doc comment? > Will fix, thanks! > > > + * Disable the efficient 8-byte reading under KMSAN to avoid false positives. > > > + */ > > > > AFAIK the CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS case is about > > unaligned accesses crossing page boundaries. In the #else case it's > > still going to do word-at-a-time if both src and dest are aligned, so > > the comment above is somewhat inaccurate. > Yes, this makes little sense. > Reading word-at-a-time shouldn't induce any errors, although it may > generate redundant stack IDs for values that will never be used. > I'll try to drop this patch. Turns out the patch is still needed, as read_word_at_a_time may read uninitialized bytes which are then used in comparisons. I've changed the patch to always set max=0 under KMSAN: https://github.com/google/kmsan/commit/3ff43863bf53dd871a3d4dc4fbb2a76d79b4db4f Will include this version in v4 series. > > > > +#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) && !defined(CONFIG_KMSAN) > > > /* > > > * If src is unaligned, don't cross a page boundary, > > > * since we don't know if the next page is mapped. > > > -- > > > 2.24.0.432.g9d3f5f5b63-goog > > > > > > > -- > 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 -- 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
next prev parent reply index Thread overview: 120+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-11-22 11:25 [PATCH RFC v3 00/36] Add KernelMemorySanitizer infrastructure glider 2019-11-22 11:25 ` [PATCH RFC v3 01/36] stackdepot: check depot_index before accessing the stack slab glider 2019-11-27 14:22 ` Marco Elver 2019-11-22 11:25 ` [PATCH RFC v3 02/36] stackdepot: build with -fno-builtin glider 2019-11-27 14:22 ` Marco Elver 2019-11-22 11:25 ` [PATCH RFC v3 03/36] kasan: stackdepot: move filter_irq_stacks() to stackdepot.c glider 2019-11-27 14:22 ` Marco Elver 2019-11-27 14:56 ` Alexander Potapenko 2019-11-22 11:25 ` [PATCH RFC v3 04/36] stackdepot: reserve 5 extra bits in depot_stack_handle_t glider 2019-11-27 14:23 ` Marco Elver 2019-11-22 11:25 ` [PATCH RFC v3 05/36] kmsan: add ReST documentation glider 2019-11-27 14:22 ` Marco Elver 2019-12-03 12:42 ` Alexander Potapenko 2019-11-22 11:25 ` [PATCH RFC v3 06/36] kmsan: gfp: introduce __GFP_NO_KMSAN_SHADOW glider 2019-11-27 14:48 ` Marco Elver 2019-12-03 12:57 ` Alexander Potapenko 2019-11-22 11:25 ` [PATCH RFC v3 07/36] kmsan: introduce __no_sanitize_memory and __SANITIZE_MEMORY__ glider 2019-11-28 13:13 ` Marco Elver 2019-11-29 16:09 ` Andrey Konovalov 2019-12-16 11:35 ` Alexander Potapenko 2019-11-22 11:25 ` [PATCH RFC v3 08/36] kmsan: reduce vmalloc space glider 2019-11-28 13:30 ` Marco Elver 2019-11-22 11:25 ` [PATCH RFC v3 09/36] kmsan: add KMSAN bits to struct page and struct task_struct glider 2019-11-28 13:44 ` Marco Elver 2019-11-28 14:05 ` Alexander Potapenko 2019-11-22 11:25 ` [PATCH RFC v3 10/36] kmsan: add KMSAN runtime glider 2019-11-24 19:44 ` Wolfram Sang 2019-11-25 9:14 ` Alexander Potapenko 2019-11-29 16:07 ` Marco Elver 2019-12-19 14:16 ` Alexander Potapenko 2019-12-02 15:39 ` Andrey Konovalov 2019-12-20 18:58 ` Alexander Potapenko 2019-12-03 14:34 ` Andrey Konovalov 2019-11-22 11:25 ` [PATCH RFC v3 11/36] kmsan: stackdepot: don't allocate KMSAN metadata for stackdepot glider 2019-11-29 14:52 ` Andrey Konovalov 2019-12-03 14:27 ` Alexander Potapenko 2019-11-22 11:25 ` [PATCH RFC v3 12/36] kmsan: define READ_ONCE_NOCHECK() glider 2019-12-02 10:03 ` Marco Elver 2019-12-03 12:45 ` Alexander Potapenko 2019-11-22 11:25 ` [PATCH RFC v3 13/36] kmsan: make READ_ONCE_TASK_STACK() return initialized values glider 2019-12-02 10:07 ` Marco Elver 2019-12-05 15:52 ` Alexander Potapenko 2019-11-22 11:25 ` [PATCH RFC v3 14/36] kmsan: x86: sync metadata pages on page fault glider 2019-11-22 11:26 ` [PATCH RFC v3 15/36] kmsan: add tests for KMSAN glider 2019-11-29 14:14 ` Andrey Konovalov 2019-12-05 14:30 ` Alexander Potapenko 2019-11-22 11:26 ` [PATCH RFC v3 16/36] crypto: kmsan: disable accelerated configs under KMSAN glider 2019-12-02 13:25 ` Marco Elver 2019-12-05 14:51 ` Alexander Potapenko 2019-11-22 11:26 ` [PATCH RFC v3 17/36] kmsan: x86: disable UNWINDER_ORC " glider 2019-12-02 13:30 ` Marco Elver 2019-11-22 11:26 ` [PATCH RFC v3 18/36] kmsan: disable LOCK_DEBUGGING_SUPPORT glider 2019-12-02 13:33 ` Marco Elver 2019-12-03 14:34 ` Alexander Potapenko 2019-12-03 15:00 ` Qian Cai 2019-12-03 15:14 ` Alexander Potapenko 2019-12-03 18:02 ` Qian Cai 2019-12-03 18:38 ` Steven Rostedt 2019-12-04 8:41 ` Alexander Potapenko 2019-12-04 12:22 ` Petr Mladek 2019-12-04 13:12 ` Qian Cai 2019-12-04 16:24 ` Alexander Potapenko 2019-12-04 18:03 ` Qian Cai 2019-11-22 11:26 ` [PATCH RFC v3 20/36] kmsan: x86: increase stack sizes in KMSAN builds glider 2019-12-02 14:31 ` Marco Elver 2019-11-22 11:26 ` [PATCH RFC v3 21/36] kmsan: disable KMSAN instrumentation for certain kernel parts glider 2019-11-29 15:07 ` Andrey Konovalov 2019-12-10 10:35 ` Alexander Potapenko 2019-12-10 12:38 ` Alexander Potapenko 2019-12-10 12:43 ` Qian Cai 2019-11-22 11:26 ` [PATCH RFC v3 22/36] kmsan: mm: call KMSAN hooks from SLUB code glider 2019-12-02 15:36 ` Marco Elver 2019-12-10 12:07 ` Alexander Potapenko 2019-11-22 11:26 ` [PATCH RFC v3 23/36] kmsan: call KMSAN hooks where needed glider 2019-11-26 10:17 ` Petr Mladek 2019-11-26 10:52 ` Alexander Potapenko 2019-11-29 16:21 ` Andrey Konovalov 2019-12-16 11:30 ` Alexander Potapenko 2019-11-22 11:26 ` [PATCH RFC v3 24/36] kmsan: disable instrumentation of certain functions glider 2019-11-29 14:59 ` Andrey Konovalov 2019-12-18 10:02 ` Alexander Potapenko 2019-11-22 11:26 ` [PATCH RFC v3 25/36] kmsan: unpoison |tlb| in arch_tlb_gather_mmu() glider 2019-11-29 15:08 ` Andrey Konovalov 2019-12-03 14:19 ` Alexander Potapenko 2019-11-22 11:26 ` [PATCH RFC v3 26/36] kmsan: use __msan_memcpy() where possible glider 2019-11-29 15:13 ` Andrey Konovalov 2019-12-05 15:46 ` Alexander Potapenko 2019-11-22 11:26 ` [PATCH RFC v3 27/36] kmsan: hooks for copy_to_user() and friends glider 2019-11-29 15:34 ` Andrey Konovalov 2019-12-05 16:00 ` Alexander Potapenko 2019-12-05 16:44 ` Andrey Konovalov 2019-12-11 14:22 ` Alexander Potapenko 2019-11-22 11:26 ` [PATCH RFC v3 28/36] kmsan: enable KMSAN builds glider 2019-11-29 15:55 ` Andrey Konovalov 2019-12-11 12:51 ` Alexander Potapenko 2019-11-22 11:26 ` [PATCH RFC v3 29/36] kmsan: handle /dev/[u]random glider 2019-11-22 11:26 ` [PATCH RFC v3 30/36] kmsan: virtio: check/unpoison scatterlist in vring_map_one_sg() glider 2019-11-22 11:26 ` [PATCH RFC v3 31/36] kmsan: disable strscpy() optimization under KMSAN glider 2019-12-02 15:51 ` Marco Elver 2019-12-02 16:23 ` Alexander Potapenko 2019-12-03 11:19 ` Alexander Potapenko [this message] 2019-12-03 11:24 ` Marco Elver 2019-12-03 11:27 ` Alexander Potapenko 2019-11-22 11:26 ` [PATCH RFC v3 32/36] kmsan: add iomap support glider 2019-12-03 12:50 ` Marco Elver 2019-12-03 14:07 ` Alexander Potapenko 2019-11-22 11:26 ` [PATCH RFC v3 33/36] kmsan: dma: unpoison memory mapped by dma_direct_map_page() glider 2019-11-22 11:26 ` [PATCH RFC v3 34/36] kmsan: disable physical page merging in biovec glider 2019-12-03 12:54 ` Marco Elver 2019-12-03 13:38 ` Alexander Potapenko 2019-11-22 11:26 ` [PATCH RFC v3 35/36] kmsan: ext4: skip block merging logic in ext4_mpage_readpages for KMSAN glider 2019-11-25 16:05 ` Robin Murphy 2019-11-25 17:03 ` Alexander Potapenko 2019-12-03 14:22 ` Marco Elver 2019-12-05 14:31 ` Alexander Potapenko 2019-11-22 11:26 ` [PATCH RFC v3 36/36] net: kasan: kmsan: support CONFIG_GENERIC_CSUM on x86, enable it for KASAN/KMSAN glider 2019-12-03 14:17 ` Marco Elver 2019-12-05 14:37 ` Alexander Potapenko 2019-11-29 14:39 ` [PATCH RFC v3 00/36] Add KernelMemorySanitizer infrastructure Marco Elver 2019-12-02 16:02 ` Alexander Potapenko
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