Linux-mm Archive on lore.kernel.org
 help / color / Atom feed
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 12:27:50 +0100
Message-ID: <CAG_fn=VNdb8WsOhsUhgbon8V_tew6dgOhh9__TBSEMB_2530bQ@mail.gmail.com> (raw)
In-Reply-To: <CANpmjNNoHyaQxgZP=iJzmA6nz_teqxRVWsuGMZLki8jeRkKS9w@mail.gmail.com>

On Tue, Dec 3, 2019 at 12:25 PM Marco Elver <elver@google.com> wrote:
>
> On Tue, 3 Dec 2019 at 12:19, Alexander Potapenko <glider@google.com> wrote:
> >
> > 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.
>
> So was the previous version working because all strscpy where this was
> relevant were unaligned?
Right.
> Re new patch: I think here it should be trivial to use 'if
> (IS_ENABLED(CONFIG_KMSAN))' instead of #ifdef.
Yes, sorry, I always forget about IS_ENABLED.
> Thanks,
> -- Marco
>
> > > > > +#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



-- 
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


  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
2019-12-03 11:24         ` Marco Elver
2019-12-03 11:27           ` Alexander Potapenko [this message]
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

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to='CAG_fn=VNdb8WsOhsUhgbon8V_tew6dgOhh9__TBSEMB_2530bQ@mail.gmail.com' \
    --to=glider@google.com \
    --cc=adilger.kernel@dilger.ca \
    --cc=akpm@linux-foundation.org \
    --cc=andreyknvl@google.com \
    --cc=ard.biesheuvel@linaro.org \
    --cc=arnd@arndb.de \
    --cc=aryabinin@virtuozzo.com \
    --cc=axboe@kernel.dk \
    --cc=cai@lca.pw \
    --cc=darrick.wong@oracle.com \
    --cc=davem@davemloft.net \
    --cc=dmitry.torokhov@gmail.com \
    --cc=dvyukov@google.com \
    --cc=ebiggers@google.com \
    --cc=edumazet@google.com \
    --cc=elver@google.com \
    --cc=ericvh@gmail.com \
    --cc=gor@linux.ibm.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=harry.wentland@amd.com \
    --cc=hch@infradead.org \
    --cc=hch@lst.de \
    --cc=herbert@gondor.apana.org.au \
    --cc=iii@linux.ibm.com \
    --cc=jasowang@redhat.com \
    --cc=linux-mm@kvack.org \
    --cc=luto@kernel.org \
    --cc=m.szyprowski@samsung.com \
    --cc=mark.rutland@arm.com \
    --cc=martin.petersen@oracle.com \
    --cc=mingo@elte.hu \
    --cc=monstr@monstr.eu \
    --cc=mst@redhat.com \
    --cc=pmladek@suse.com \
    --cc=rdunlap@infradead.org \
    --cc=robin.murphy@arm.com \
    --cc=rostedt@goodmis.org \
    --cc=schwidefsky@de.ibm.com \
    --cc=sergey.senozhatsky@gmail.com \
    --cc=tglx@linutronix.de \
    --cc=tiwai@suse.com \
    --cc=tytso@mit.edu \
    --cc=vegard.nossum@oracle.com \
    --cc=viro@zeniv.linux.org.uk \
    --cc=willy@infradead.org \
    --cc=wsa@the-dreams.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-mm Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mm/0 linux-mm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mm linux-mm/ https://lore.kernel.org/linux-mm \
		linux-mm@kvack.org
	public-inbox-index linux-mm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kvack.linux-mm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git