m68k: Make sys_atomic_cmpxchg_32 work on classic m68k

commit 9e2760d18b3cf179534bbc27692c84879c61b97c upstream.

User space access must always go through uaccess accessors, since on
classic m68k user space and kernel space are completely separate.

Signed-off-by: Andreas Schwab <schwab@linux-m68k.org>
Tested-by: Thorsten Glaser <tg@debian.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/m68k/kernel/sys_m68k.c b/arch/m68k/kernel/sys_m68k.c
index 8623f8dc16f8a03c9da88910537ae93fc47bc510..9a5932ec368946bf808c5faf527cbf39731b5540 100644 (file)
--- a/arch/m68k/kernel/sys_m68k.c
+++ b/arch/m68k/kernel/sys_m68k.c
@@ -479,9 +479,13 @@ sys_atomic_cmpxchg_32(unsigned long newval, int oldval, int d3, int d4, int d5,
                        goto bad_access;
                }
 
-               mem_value = *mem;
+               /*
+                * No need to check for EFAULT; we know that the page is
+                * present and writable.
+                */
+               __get_user(mem_value, mem);
                if (mem_value == oldval)
-                       *mem = newval;
+                       __put_user(newval, mem);
 
                pte_unmap_unlock(pte, ptl);
                up_read(&mm->mmap_sem);