Re: [PATCH 2/2] x86: fix __user annotations

Jann Horn
2019-03-29T16:02:36Z

On Fri, Mar 29, 2019 at 2:39 PM Borislav Petkov <bp@alien8.de> wrote:
>
> On Thu, Mar 28, 2019 at 10:23:21PM +0100, Jann Horn wrote:
> > Fix __user annotations in various places across the x86 tree:
> >
> > - cast to wrong pointer type in __user_atomic_cmpxchg_inatomic()
> > - generic_load_microcode() deals with a pointer that can be either a
> > kernel pointer or a user pointer; change the code to pass it around as
> > a __user pointer, and add explicit casts to convert between __user and
> > __kernel
> > - save_xstate_epilog() has missing __user in explicit casts
> > - setup_sigcontext() and x32_setup_rt_frame() rely on the cast performed
> > by put_user_ex() on its first argument, but sparse requires __force for
> > casting __user pointers to unsigned long
> > - xen_hvm_config() has missing __user
> >
> > This patch removes all sparse warnings about the asn:1 address space
> > (__user) in arch/x86/ for my kernel config.
> >
> > Signed-off-by: Jann Horn <jannh@google.com>
> > ---
> > This patch requires the previous one, "[PATCH 1/2] kernel.h: use
> > parentheses around argument in u64_to_user_ptr()", otherwise
> > xen_hvm_config() breaks. Can we take both together through the x86 tree,
> > or does the first one have to go through akpm's tree?
>
> I don't see why not, unless akpm has objections.
>
> However,
>
> > arch/x86/include/asm/uaccess.h | 3 +--
> > arch/x86/include/asm/uaccess_64.h | 2 +-
>
> This chunk is being discussed here already:
>
> https://lkml.kernel.org/r/20190228185027.2480-1-ben.dooks@codethink.co.uk
>
> and I'd like to take Ben's v2 when Ben adds Linus' explanation.

Alright, dropped the changes in:
arch/x86/lib/usercopy_64.c
arch/x86/include/asm/uaccess_64.h

> Then, it would be probably easier if you could split that patch into:
>
> > arch/x86/kernel/cpu/microcode/intel.c | 20 ++++++++++++--------
>
> microcode
>
> > arch/x86/kernel/fpu/signal.c | 6 +++---
> > arch/x86/kernel/signal.c | 4 ++--
>
> fpu patch
>
> > arch/x86/kvm/x86.c | 8 ++++----

Split these out as suggested. Additionally, I've split out one commit
for x86/uaccess (the change to arch/x86/include/asm/uaccess.h wasn't
in Ben's patch).

> kvm patch

Actually, looking at the log of that file, and at MAINTAINERS, it
looks like that should go through the KVM tree? There's also something
I want to fix in virt/kvm/kvm_main.c, so I have to send some stuff to
Paolo anyway.