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Re: [PATCH v3] mm/usercopy: get rid of CONFIG_DEBUG_STRICT_USER_COPY_CHECKS

From Mark Rutland <mark.rutland@arm.com>
Newsgroups linux.kernel
Subject Re: [PATCH v3] mm/usercopy: get rid of CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
Date 2016-08-31 11:50 +0200
Message-ID <scajE-HB-27@gated-at.bofh.it> (permalink)
References <sbyel-1BC-11@gated-at.bofh.it> <sbQXD-5kV-23@gated-at.bofh.it> <sbUHT-7Jg-1@gated-at.bofh.it> <sbVND-8n7-9@gated-at.bofh.it> <sbXFL-1b9-1@gated-at.bofh.it>
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On Tue, Aug 30, 2016 at 09:13:32PM +0100, Al Viro wrote:
> On Tue, Aug 30, 2016 at 02:15:58PM -0400, Kees Cook wrote:
> 
> > First, some current API usage which we'll need to maintain at least
> > for now: __copy_*_user() is just copy_*_user() without the access_ok()
> > checks. Unfortunately, some arch implement different copying methods
> > depending on if the entry is via copy...() or __copy..() (e.g. see
> > x86's use of _copy...() -- single underscore??) There doesn't seem to
> > be a good reason for this, and I think it would make sense to extract
> > the actual per-arch implementation that performs the real copy into
> > something like arm64's __arch_copy_*_user(), which only does the copy
> > itself and nothing else.
> 
> No.  __arch_copy_from_user() is a bloody bad idea; the real primitive
> is what's currently called __copy_from_user_inatomic(), and I'm planning
> to rename it to raw_copy_from_user(). 

Great!

FWIW, my plan with the arch_* forms was to follow the convention set by
the spinlock code and have raw_* forms build atop of these, where common
debug and/or hardening checks would live.

From my PoV, anything to make this more consistent cross-architecture is
good, especially if we can pull the duplicated logic into common code.

Thanks,
Mark.

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Re: [PATCH 2/2] mm/usercopy: enable usercopy size checking for  modern versions of gcc Josh Poimboeuf <jpoimboe@redhat.com> - 2016-08-25 23:00 +0200
  Re: [PATCH 2/2] mm/usercopy: enable usercopy size checking for modern  versions of gcc Kees Cook <keescook@chromium.org> - 2016-08-26 04:30 +0200
    Re: [PATCH 2/2] mm/usercopy: enable usercopy size checking for  modern versions of gcc Josh Poimboeuf <jpoimboe@redhat.com> - 2016-08-26 06:00 +0200
      Re: [PATCH 2/2] mm/usercopy: enable usercopy size checking for modern  versions of gcc Kees Cook <keescook@chromium.org> - 2016-08-26 15:50 +0200
        Re: [PATCH 2/2] mm/usercopy: enable usercopy size checking for  modern versions of gcc Josh Poimboeuf <jpoimboe@redhat.com> - 2016-08-26 16:00 +0200
          Re: [PATCH 2/2] mm/usercopy: enable usercopy size checking for  modern versions of gcc Josh Poimboeuf <jpoimboe@redhat.com> - 2016-08-26 23:10 +0200
            Re: [PATCH 2/2] mm/usercopy: enable usercopy size checking for  modern versions of gcc Josh Poimboeuf <jpoimboe@redhat.com> - 2016-08-26 23:10 +0200
            Re: [PATCH 2/2] mm/usercopy: enable usercopy size checking for modern  versions of gcc Linus Torvalds <torvalds@linux-foundation.org> - 2016-08-27 02:40 +0200
              Re: [PATCH 2/2] mm/usercopy: enable usercopy size checking for  modern versions of gcc Josh Poimboeuf <jpoimboe@redhat.com> - 2016-08-29 16:50 +0200
                Re: [PATCH 2/2] mm/usercopy: enable usercopy size checking for modern  versions of gcc Linus Torvalds <torvalds@linux-foundation.org> - 2016-08-29 17:40 +0200
                [PATCH v2] mm/usercopy: get rid of  CONFIG_DEBUG_STRICT_USER_COPY_CHECKS Josh Poimboeuf <jpoimboe@redhat.com> - 2016-08-29 19:10 +0200
                Re: [PATCH v2] mm/usercopy: get rid of  CONFIG_DEBUG_STRICT_USER_COPY_CHECKS Josh Poimboeuf <jpoimboe@redhat.com> - 2016-08-29 20:10 +0200
                [PATCH v3] mm/usercopy: get rid of CONFIG_DEBUG_STRICT_USER_COPY_CHECKS Josh Poimboeuf <jpoimboe@redhat.com> - 2016-08-30 15:10 +0200
                Re: [PATCH v3] mm/usercopy: get rid of CONFIG_DEBUG_STRICT_USER_COPY_CHECKS Linus Torvalds <torvalds@linux-foundation.org> - 2016-08-30 19:10 +0200
                Re: [PATCH v3] mm/usercopy: get rid of CONFIG_DEBUG_STRICT_USER_COPY_CHECKS Kees Cook <keescook@chromium.org> - 2016-08-30 20:20 +0200
                Re: [PATCH v3] mm/usercopy: get rid of  CONFIG_DEBUG_STRICT_USER_COPY_CHECKS Josh Poimboeuf <jpoimboe@redhat.com> - 2016-08-30 21:10 +0200
                Re: [PATCH v3] mm/usercopy: get rid of CONFIG_DEBUG_STRICT_USER_COPY_CHECKS Kees Cook <keescook@chromium.org> - 2016-08-30 21:30 +0200
                Re: [PATCH v3] mm/usercopy: get rid of  CONFIG_DEBUG_STRICT_USER_COPY_CHECKS Al Viro <viro@ZenIV.linux.org.uk> - 2016-08-30 22:20 +0200
                Re: [PATCH v3] mm/usercopy: get rid of CONFIG_DEBUG_STRICT_USER_COPY_CHECKS Kees Cook <keescook@chromium.org> - 2016-08-31 00:30 +0200
                Re: [PATCH v3] mm/usercopy: get rid of  CONFIG_DEBUG_STRICT_USER_COPY_CHECKS Mark Rutland <mark.rutland@arm.com> - 2016-08-31 11:50 +0200
                Re: [PATCH v3] mm/usercopy: get rid of CONFIG_DEBUG_STRICT_USER_COPY_CHECKS Linus Torvalds <torvalds@linux-foundation.org> - 2016-08-30 20:20 +0200
                Re: [PATCH v3] mm/usercopy: get rid of  CONFIG_DEBUG_STRICT_USER_COPY_CHECKS Al Viro <viro@ZenIV.linux.org.uk> - 2016-08-30 20:20 +0200
                Re: [PATCH 2/2] mm/usercopy: enable usercopy size checking for modern  versions of gcc Kees Cook <keescook@chromium.org> - 2016-08-30 20:40 +0200

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