linux-kernel - Re: [PATCH] RISC-V: Fix raw_copy_{to,from}

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Date:   Thu, 15 Nov 2018 12:27:42 -0800
From:   Olof Johansson <olof@...om.net>
To:     Palmer Dabbelt <palmer@...ive.com>
Cc:     Albert Ou <aou@...s.berkeley.edu>, linux-riscv@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] RISC-V: Fix raw_copy_{to,from}_user()

On Thu, Nov 15, 2018 at 6:59 AM Palmer Dabbelt <palmer@...ive.com> wrote:
>
> On Wed, 14 Nov 2018 16:27:55 PST (-0800), Olof Johansson wrote:
> > Sparse highlighted it, and appears to be a pure bug (from vs to).
> >
> > ./arch/riscv/include/asm/uaccess.h:403:35: warning: incorrect type in argument 1 (different address spaces)
> > ./arch/riscv/include/asm/uaccess.h:403:39: warning: incorrect type in argument 2 (different address spaces)
> > ./arch/riscv/include/asm/uaccess.h:409:37: warning: incorrect type in argument 1 (different address spaces)
> > ./arch/riscv/include/asm/uaccess.h:409:41: warning: incorrect type in argument 2 (different address spaces)
> >
> > Signed-off-by: Olof Johansson <olof@...om.net>
> > ---
> >  arch/riscv/include/asm/uaccess.h | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
> > index 473cfc84e412f..8c3e3e3c8be12 100644
> > --- a/arch/riscv/include/asm/uaccess.h
> > +++ b/arch/riscv/include/asm/uaccess.h
> > @@ -400,13 +400,13 @@ extern unsigned long __must_check __asm_copy_from_user(void *to,
> >  static inline unsigned long
> >  raw_copy_from_user(void *to, const void __user *from, unsigned long n)
> >  {
> > -     return __asm_copy_to_user(to, from, n);
> > +     return __asm_copy_from_user(to, from, n);
> >  }
> >
> >  static inline unsigned long
> >  raw_copy_to_user(void __user *to, const void *from, unsigned long n)
> >  {
> > -     return __asm_copy_from_user(to, from, n);
> > +     return __asm_copy_to_user(to, from, n);
> >  }
> >
> >  extern long strncpy_from_user(char *dest, const char __user *src, long count);
>
> Oh, no idea how I missed that one.  This looks like it's been in for a long
> time, so I'm surprised anything works at all!

Actually, it boils down to a memcpy either way, it's just that
exceptions and access control isn't handled right. So as long as you
always do valid copying you'll luck out.

> I'm going to add a stable CC and PR this to Linus this week, assuming I get
> some time to at least give it a minimal test.
>
> Thanks for catching this!

Cool, sounds good.


-Olof