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Re: [PATCH] [iov_iter] use memmove() when copying to/from user page

From Al Viro <viro@ZenIV.linux.org.uk>
Newsgroups linux.kernel
Subject Re: [PATCH] [iov_iter] use memmove() when copying to/from user page
Date 2017-05-16 20:50 +0200
Message-ID <tHPHI-IC-11@gated-at.bofh.it> (permalink)
References <tHJLZ-5yL-37@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Tue, May 16, 2017 at 02:27:34PM +0200, Alexander Potapenko wrote:
> It's possible that calling sendfile() to copy the data from a memfd to
> itself may result in doing a memcpy() with overlapping arguments.
> To avoid undefined behavior here, replace memcpy() with memmove() and
> rename memcpy_to_page()/memcpy_from_page() accordingly.

Er...  And what semantics would you assign to such sendfile()?  I really
want to see details, because it sounds like memmove() here will not be
any more useful than memcpy() - you still can esily get odd behaviour.

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[PATCH] [iov_iter] use memmove() when copying to/from user page Alexander Potapenko <glider@google.com> - 2017-05-16 14:30 +0200
  Re: [PATCH] [iov_iter] use memmove() when copying to/from user page Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-16 20:50 +0200
    Re: [PATCH] [iov_iter] use memmove() when copying to/from user page Dmitry Vyukov <dvyukov@google.com> - 2017-05-16 21:00 +0200
      Re: [PATCH] [iov_iter] use memmove() when copying to/from user page Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-16 21:40 +0200
        Re: [PATCH] [iov_iter] use memmove() when copying to/from user page Dmitry Vyukov <dvyukov@google.com> - 2017-05-16 22:20 +0200
          Re: [PATCH] [iov_iter] use memmove() when copying to/from user page Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-16 23:00 +0200
            Re: [PATCH] [iov_iter] use memmove() when copying to/from user page Dmitry Vyukov <dvyukov@google.com> - 2017-05-16 23:10 +0200
              Re: [PATCH] [iov_iter] use memmove() when copying to/from user page Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-16 23:40 +0200
                Re: [PATCH] [iov_iter] use memmove() when copying to/from user page Dmitry Vyukov <dvyukov@google.com> - 2017-05-17 00:20 +0200
                Re: [PATCH] [iov_iter] use memmove() when copying to/from user page Al Viro <viro@ZenIV.linux.org.uk> - 2017-05-17 00:50 +0200

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