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

On Tue, Jul 27, 2021 at 7:27 PM Heiko Carstens [off-list ref] wrote:

On Tue, Jul 27, 2021 at 04:48:57PM +0200, Arnd Bergmann wrote:

quoted

---
 include/linux/compat.h |  17 ++--
 mm/mempolicy.c         | 175 +++++++++++++----------------------------
 2 files changed, 63 insertions(+), 129 deletions(-)

...

quoted

+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.

        Arnd

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