x86: rename and clean up __copy_from_user_inatomic_nocache()

Similarly to the previous commit, this renames the somewhat confusingly
named function.  But in this case, it was at least less confusing: the
__copy_from_user_inatomic_nocache is indeed copying from user memory,
and it is indeed ok to be used in an atomic context, so it will not warn
about it.

But the previous commit also removed the NTB mis-use of the
__copy_from_user_inatomic_nocache() function, and as a result every
call-site is now _actually_ doing a real user copy.  That means that we
can now do the proper user pointer verification too.

End result: add proper address checking, remove the double underscores,
and change the "nocache" to "nontemporal" to more accurately describe
what this x86-only function actually does.  It might be worth noting
that only the target is non-temporal: the actual user accesses are
normal memory accesses.

Also worth noting is that non-x86 targets (and on older 32-bit x86 CPU's
before XMM2 in the Pentium III) we end up just falling back on a regular
user copy, so nothing can actually depend on the non-temporal semantics,
but that has always been true.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 3 deletions

diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 1f3804245c06..4c7d0b815093 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -331,16 +331,21 @@ static inline size_t probe_subpage_writeable(char __user *uaddr, size_t size)
 
 #endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */
 
-#ifndef ARCH_HAS_NOCACHE_UACCESS
+#ifndef ARCH_HAS_NONTEMPORAL_UACCESS
 
 static inline __must_check unsigned long
-__copy_from_user_inatomic_nocache(void *to, const void __user *from,
+copy_from_user_inatomic_nontemporal(void *to, const void __user *from,
 				  unsigned long n)
 {
+	if (can_do_masked_user_access())
+		from = mask_user_address(from);
+	else
+		if (!access_ok(from, n))
+			return n;
 	return __copy_from_user_inatomic(to, from, n);
 }
 
-#endif		/* ARCH_HAS_NOCACHE_UACCESS */
+#endif		/* ARCH_HAS_NONTEMPORAL_UACCESS */
 
 extern __must_check int check_zeroed_user(const void __user *from, size_t size);