signal: Correct the offset of si_pkey in struct siginfo

The change moving addr_lsb into the _sigfault union failed to take
into account that _sigfault._addr_bnd._lower being a pointer forced
the entire union to have pointer alignment.  In practice this only
mattered for the offset of si_pkey which is why this has taken so long
to discover.

To correct this change _dummy_pkey and _dummy_bnd to have pointer type.
Reported-by: Nkernel test robot <shun.hao@intel.com>
Fixes: b68a68d3 ("signal: Move addr_lsb into the _sigfault union for clarity")
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>

include/linux/compat.h

@@ -229,13 +229,13 @@ typedef struct compat_siginfo {
 				short int _addr_lsb;	/* Valid LSB of the reported address. */
 				/* used when si_code=SEGV_BNDERR */
 				struct {
-					short _dummy_bnd;
+					compat_uptr_t _dummy_bnd;
 					compat_uptr_t _lower;
 					compat_uptr_t _upper;
 				} _addr_bnd;
 				/* used when si_code=SEGV_PKUERR */
 				struct {
-					short _dummy_pkey;
+					compat_uptr_t _dummy_pkey;
 					u32 _pkey;
 				} _addr_pkey;
 			};

include/uapi/asm-generic/siginfo.h

@@ -102,13 +102,13 @@ typedef struct siginfo {
 				short _addr_lsb; /* LSB of the reported address */
 				/* used when si_code=SEGV_BNDERR */
 				struct {
-					short _dummy_bnd;
+					void *_dummy_bnd;
 					void __user *_lower;
 					void __user *_upper;
 				} _addr_bnd;
 				/* used when si_code=SEGV_PKUERR */
 				struct {
-					short _dummy_pkey;
+					void *_dummy_pkey;
 					__u32 _pkey;
 				} _addr_pkey;
 			};