On Thu, Jan 30, 2025 at 04:47:00PM +0100, Jens Remus wrote:

On 22.01.2025 03:31, Josh Poimboeuf wrote:

quoted

+struct sframe_fre {
+	unsigned int	size;
+	s32		ip_off;

The IP offset (from function start) in the SFrame V2 FDE is unsigned:

u32 ip_off;

Indeed.

quoted

+#define __UNSAFE_GET_USER_INC(to, from, type, label)			\
+({									\
+	type __to;							\
+	unsafe_get_user(__to, (type __user *)from, label);		\
+	from += sizeof(__to);						\
+	to = (typeof(to))__to;							\
+})
+
+#define UNSAFE_GET_USER_INC(to, from, size, label)			\
+({									\
+	switch (size) {							\
+	case 1:								\
+		__UNSAFE_GET_USER_INC(to, from, u8, label);		\
+		break;							\
+	case 2:								\
+		__UNSAFE_GET_USER_INC(to, from, u16, label);		\
+		break;							\
+	case 4:								\
+		__UNSAFE_GET_USER_INC(to, from, u32, label);		\
+		break;							\
+	default:							\
+		return -EFAULT;						\
+	}								\
+})

This does not work for the signed SFrame fields, such as the FRE CFA,
RA, and FP offsets, as it does not perform the required sign extension.
One option would be to rename to UNSAFE_GET_USER_UNSIGNED_INC() and
re-introduce UNSAFE_GET_USER_SIGNED_INC() using s8, s16, and s32.

See the following line in __UNSAFE_GET_USER_INC():

	to = (typeof(to))__to;

Does that not do the sign extension?

-- 
Josh