Patch "arm64: uaccess: ensure extension of access_ok() addr" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

arm64: uaccess: ensure extension of access_ok() addr

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
arm64-uaccess-ensure-extension-of-access_ok-addr.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Mark Rutland <[email protected]>
Date: Wed, 3 May 2017 16:09:35 +0100
Subject: arm64: uaccess: ensure extension of access_ok() addr

From: Mark Rutland <[email protected]>

commit a06040d7a791a9177581dcf7293941bd92400856 upstream.

Our access_ok() simply hands its arguments over to __range_ok(), which implicitly assummes that the addr parameter is 64 bits wide. This isn't necessarily true for compat code, which might pass down a 32-bit address parameter.

In these cases, we don't have a guarantee that the address has been zero extended to 64 bits, and the upper bits of the register may contain unknown values, potentially resulting in a suprious failure.

Avoid this by explicitly casting the addr parameter to an unsigned long (as is done on other architectures), ensuring that the parameter is widened appropriately.

---
 arch/arm64/include/asm/uaccess.h |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

@@ -93,11 +93,12 @@ static inline void set_fs(mm_segment_t f
  */
 #define __range_ok(addr, size)						\
 ({									\
+	unsigned long __addr = (unsigned long __force)(addr);		\
 	unsigned long flag, roksum;					\
 	__chk_user_ptr(addr);						\
 	asm("adds %1, %1, %3; ccmp %1, %4, #2, cc; cset %0, ls"		\
 		: "=&r" (flag), "=&r" (roksum)				\
-		: "1" (addr), "Ir" (size),				\
+		: "1" (__addr), "Ir" (size),				\
 		  "r" (current_thread_info()->addr_limit)		\
 		: "cc");						\
 	flag;								\

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/arm64-armv8_deprecated-ensure-extension-of-addr.patch queue-4.9/arm64-uaccess-ensure-extension-of-access_ok-addr.patch queue-4.9/arm64-xchg-hazard-against-entire-exchange-variable.patch queue-4.9/arm64-ensure-extension-of-smp_store_release-value.patch