Re: [PATCH v5 4/6] mm: simplify compat numa syscalls

Heiko Carstens
2021-07-27T18:40:02Z

On Tue, Jul 27, 2021 at 07:40:05PM +0200, Arnd Bergmann wrote:
> On Tue, Jul 27, 2021 at 7:27 PM Heiko Carstens <hca@linux.ibm.com> wrote:
> > > +static int get_bitmap(unsigned long *mask, const unsigned long __user *nmask,
> > > + unsigned long maxnode)
> > > +{
> > > + unsigned long nlongs = BITS_TO_LONGS(maxnode);
> > > + int ret;
> > > +
> > > + if (in_compat_syscall())
> > > + ret = compat_get_bitmap(mask,
> > > + (const compat_ulong_t __user *)nmask,
> > > + maxnode);
> >
> > compat_ptr() conversion for e.g. nmask is missing with the next patch
> > which removes the compat system calls.
> > Is that intended or am I missing something?
>
> I don't think it's needed here, since the pointer comes from the system
> call argument, which has the compat_ptr() conversion applied in
> arch/s390/include/asm/syscall_wrapper.h, not from a compat_uptr_t
> that gets passed indirectly. The compat_get_bitmap() conversion
> is only needed for byte order adjustment, not for converting pointers.
>
> It's also possible that I'm the one who's missing something.

What I was trying to say: this patch on its own is ok. However with
the next patch you remove the compat system calls and map the regular
system calls instead.

That is:

-COMPAT_SYSCALL_DEFINE6(mbind, compat_ulong_t, start, compat_ulong_t, len,
- compat_ulong_t, mode, compat_ulong_t __user *, nmask,
- compat_ulong_t, maxnode, compat_ulong_t, flags)
-{
- return kernel_mbind(start, len, mode, (unsigned long __user *)nmask,
- maxnode, flags);
-}

and this:

-268 common mbind sys_mbind compat_sys_mbind
-269 common get_mempolicy sys_get_mempolicy compat_sys_get_mempolicy
-270 common set_mempolicy sys_set_mempolicy compat_sys_set_mempolicy
+268 common mbind sys_mbind sys_mbind
+269 common get_mempolicy sys_get_mempolicy sys_get_mempolicy
+270 common set_mempolicy sys_set_mempolicy sys_set_mempolicy

would remove compat_ptr() conversion from nmask above if I'm not mistaken.