Merge branch 'nocache-cleanup'

This series cleans up some of the special user copy functions naming and
semantics.  In particular, get rid of the (very traditional) double
underscore names and behavior: the whole "optimize away the range check"
model has been largely excised from the other user accessors because
it's so subtle and can be unsafe, but also because it's just not a
relevant optimization any more.

To do that, a couple of drivers that misused the "user" copies as kernel
copies in order to get non-temporal stores had to be fixed up, but that
kind of code should never have been allowed anyway.

The x86-only "nocache" version was also renamed to more accurately
reflect what it actually does.

This was all done because I looked at this code due to a report by Jann
Horn, and I just couldn't stand the inconsistent naming, the horrible
semantics, and the random misuse of these functions.  This code should
probably be cleaned up further, but it's at least slightly closer to
normal semantics.

I had a more intrusive series that went even further in trying to
normalize the semantics, but that ended up hitting so many other
inconsistencies between different architectures in this area (eg
'size_t' vs 'unsigned long' vs 'int' as size arguments, and various
iovec check differences that Vasily Gorbik pointed out) that I ended up
with this more limited version that fixed the worst of the issues.

Reported-by: Jann Horn <jannh@google.com>
Tested-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/all/CAHk-=wgg1QVWNWG-UCFo1hx0zqrPnB3qhPzUTrWNft+MtXQXig@mail.gmail.com/

* nocache-cleanup:
  x86-64/arm64/powerpc: clean up and rename __copy_from_user_flushcache
  x86: rename and clean up __copy_from_user_inatomic_nocache()
  x86-64: rename misleadingly named '__copy_user_nocache()' function

1 files changed, 8 insertions, 3 deletions

diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 4fe63169d5a2..56328601218c 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);