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From: Dan Williams <dan.j.williams@intel.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: "Weiny, Ira" <ira.weiny@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Christoph Hellwig <hch@infradead.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Eric Biggers <ebiggers@kernel.org>,
	Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH V2 2/2] mm/highmem: Lift memcpy_[to|from]_page to core
Date: Mon, 7 Dec 2020 15:34:44 -0800	[thread overview]
Message-ID: <CAPcyv4hkY-9V5Rq5s=BRku2AeWYtgs9DuVXnhdEkara2NiN9Tg@mail.gmail.com> (raw)
In-Reply-To: <20201207232649.GD7338@casper.infradead.org>

On Mon, Dec 7, 2020 at 3:27 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Dec 07, 2020 at 02:57:03PM -0800, ira.weiny@intel.com wrote:
> > +static inline void memcpy_page(struct page *dst_page, size_t dst_off,
> > +                            struct page *src_page, size_t src_off,
> > +                            size_t len)
> > +{
> > +     char *dst = kmap_local_page(dst_page);
> > +     char *src = kmap_local_page(src_page);
>
> I appreciate you've only moved these, but please add:
>
>         BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);

I imagine it's not outside the realm of possibility that some driver
on CONFIG_HIGHMEM=n is violating this assumption and getting away with
it because kmap_atomic() of contiguous pages "just works (TM)".
Shouldn't this WARN rather than BUG so that the user can report the
buggy driver and not have a dead system?

  reply	other threads:[~2020-12-07 23:35 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-07 22:57 [PATCH V2 0/2] Lift memcpy_[to|from]_page to core ira.weiny
2020-12-07 22:57 ` [PATCH V2 1/2] mm/highmem: Remove deprecated kmap_atomic ira.weiny
2020-12-08  0:22   ` kernel test robot
2020-12-08  0:22     ` kernel test robot
2020-12-07 22:57 ` [PATCH V2 2/2] mm/highmem: Lift memcpy_[to|from]_page to core ira.weiny
2020-12-07 23:26   ` Matthew Wilcox
2020-12-07 23:34     ` Dan Williams [this message]
2020-12-07 23:40       ` Matthew Wilcox
2020-12-07 23:49         ` Dan Williams
2020-12-08 21:32           ` Ira Weiny
2020-12-08 21:50             ` Matthew Wilcox
2020-12-08 22:23               ` Dan Williams
2020-12-08 22:32                 ` Matthew Wilcox
2020-12-08 22:45                   ` Darrick J. Wong
2020-12-08 22:54                     ` Matthew Wilcox
2020-12-08 23:40                     ` Dan Williams
2020-12-09  2:22                       ` Ira Weiny
2020-12-09  4:03                         ` Matthew Wilcox
2020-12-09 19:47                           ` Dan Williams
2020-12-09 20:14                             ` Matthew Wilcox
2020-12-09 20:19                               ` Dan Williams
2020-12-10  5:35                               ` Ira Weiny
2020-12-08 22:21             ` Dan Williams
2020-12-08  0:40   ` kernel test robot
2020-12-08  0:40     ` kernel test robot
2020-12-08  1:09   ` kernel test robot
2020-12-08  1:09     ` kernel test robot
2020-12-08 12:23   ` Matthew Wilcox
2020-12-08 16:38     ` Ira Weiny
2020-12-08 16:40       ` Matthew Wilcox

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