[PATCH] arm64: compat: fix compat types affecting struct compat_elf_prpsinfo

[Catalin Marinas]

On Tue, Oct 14, 2014 at 10:29:14AM +0100, Arnd Bergmann wrote:
> On Tuesday 14 October 2014 09:51:25 Catalin Marinas wrote:
> > On Tue, Oct 14, 2014 at 06:55:05AM +0100, Victor Kamensky wrote:
> > > The compat_elf_prpsinfo structure does not match the arch/arm struct
> > > elf_pspsinfo definition. As result NT_PRPSINFO note in core file
> > > created by arm64 kernel for aarch32 (compat) process has wrong size.
> > > So gdb cannot display command that caused process crash.
> > > 
> > > Fix is to change size of __compat_uid_t, __compat_gid_t so it would
> > > match size of similar fields in arch/arm case.
> > > 
> > > Signed-off-by: Victor Kamensky <victor.kamensky at linaro.org>
> > > ---
> > >  arch/arm64/include/asm/compat.h | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/arch/arm64/include/asm/compat.h b/arch/arm64/include/asm/compat.h
> > > index 253e33b..56de5aa 100644
> > > --- a/arch/arm64/include/asm/compat.h
> > > +++ b/arch/arm64/include/asm/compat.h
> > > @@ -37,8 +37,8 @@ typedef s32         compat_ssize_t;
> > >  typedef s32          compat_time_t;
> > >  typedef s32          compat_clock_t;
> > >  typedef s32          compat_pid_t;
> > > -typedef u32          __compat_uid_t;
> > > -typedef u32          __compat_gid_t;
> > > +typedef u16          __compat_uid_t;
> > > +typedef u16          __compat_gid_t;
> > >  typedef u16          __compat_uid16_t;
> > >  typedef u16          __compat_gid16_t;
> > >  typedef u32          __compat_uid32_t;
> > 
> > __compat_uid_t is defined to match the arm32 uid_t and that would be
> > __kernel_uid32_t (or __compat_uid32_t). So this is not the correct fix.
> 
> No, I think Victor is right: __compat_uid_t should match the arm32
> __kernel_uid_t, not the arm32 uid_t, which is just a kernel-internal
> definition, while the __kernel_uid_t is the one used in all user
> visible interfaces.

Ah, I think you are right. The compat_uid_t (without underscores) should
match the arm32 uid_t while __compat_uid_t would match arm32
__kernel_uid_t.

> The definition in your asm/compat.h file seems to be a mistake.

What's weird is that 32-bit LTP on top of the arm64 kernel hasn't caught
this for the past years.

> > The problem is that elf_prpsinfo uses __kernel_uid_t which arm32 defines
> > as (unsigned short) while compat_elf_prspinfo uses __compat_uid_t which
> > is 32-bit. In reality compat_uid_t is different from the arm32
> > kernel_uid_t (other 32-bit architectures may use a 32-bit kernel_uid_t).
> 
> compat_uid_t should match the __kernel_uid_t for all 32-bit architectures
> that are emulated on a 64-bit architecture, that is the definition.

I guess you meant __compat_uid_t here. The compat_uid_t type is u32
already.

So that patch is fine, I'll take it for 3.17 (and cc stable all the way
back to 3.7).

Thanks.

-- 
Catalin