arm64: uaccess: ensure extension of access_ok() addr

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@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 55d0adb..14cca10 100644 (file)
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -93,11 +93,12 @@ static inline void set_fs(mm_segment_t fs)
  */
 #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;                                                           \