linux-kernel - [PATCH 4.4 085/103] arm64: uaccess: ensure extension of access

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Message-Id: <20170523200903.294157512@linuxfoundation.org>
Date:   Tue, 23 May 2017 22:09:51 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>
Subject: [PATCH 4.4 085/103] arm64: uaccess: ensure extension of access_ok() addr

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mark Rutland <mark.rutland@....com>

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.

Fixes: 0aea86a2176c ("arm64: User access library functions")
Acked-by: Will Deacon <will.deacon@....com>
Signed-off-by: Mark Rutland <mark.rutland@....com>
Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -92,11 +92,12 @@ 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;								\