diff --git a/firmware/2lib/2common.c b/firmware/2lib/2common.c
index 9099f6f..56593aa 100644
--- a/firmware/2lib/2common.c
+++ b/firmware/2lib/2common.c
@@ -20,14 +20,14 @@
 		offs = align - offs;
 
 		if (*size < offs)
-			return VB2_ERROR_BUFFER_TOO_SMALL;
+			return VB2_ERROR_ALIGN_BIGGER_THAN_SIZE;
 
 		*ptr += offs;
 		*size -= offs;
 	}
 
 	if (*size < want_size)
-		return VB2_ERROR_BUFFER_TOO_SMALL;
+		return VB2_ERROR_ALIGN_SIZE;
 
 	return VB2_SUCCESS;
 }
@@ -106,10 +106,10 @@
 	return (uintptr_t)ptr - (uintptr_t)base;
 }
 
-int vb2_verify_member_inside(const void *parent, uint32_t parent_size,
-			     const void *member, uint32_t member_size,
-			     uint32_t member_data_offset,
-			     uint32_t member_data_size)
+int vb2_verify_member_inside(const void *parent, size_t parent_size,
+			     const void *member, size_t member_size,
+			     ptrdiff_t member_data_offset,
+			     size_t member_data_size)
 {
 	const size_t psize = (size_t)parent_size;
 	const uintptr_t parent_end = (uintptr_t)parent + parent_size;
@@ -120,23 +120,22 @@
 
 	/* Make sure parent doesn't wrap */
 	if (parent_end < (uintptr_t)parent)
-		return VB2_ERROR_UNKNOWN;
+		return VB2_ERROR_INSIDE_PARENT_WRAPS;
 
 	/*
 	 * Make sure the member is fully contained in the parent and doesn't
 	 * wrap.  Use >, not >=, since member_size = 0 is possible.
 	 */
 	if (member_end_offs < member_offs)
-		return VB2_ERROR_UNKNOWN;
-	if (member_offs > psize || member_end_offs > psize)
-		return VB2_ERROR_UNKNOWN;
-
+		return VB2_ERROR_INSIDE_MEMBER_WRAPS;
+	if (member_offs < 0 || member_offs > psize || member_end_offs > psize)
+		return VB2_ERROR_INSIDE_MEMBER_OUTSIDE;
 
 	/* Make sure parent fully contains member data */
 	if (data_end_offs < data_offs)
-		return VB2_ERROR_UNKNOWN;
-	if (data_offs > psize || data_end_offs > psize)
-		return VB2_ERROR_UNKNOWN;
+		return VB2_ERROR_INSIDE_DATA_WRAPS;
+	if (data_offs < 0 || data_offs > psize || data_end_offs > psize)
+		return VB2_ERROR_INSIDE_DATA_OUTSIDE;
 
 	return VB2_SUCCESS;
 }
diff --git a/firmware/2lib/include/2common.h b/firmware/2lib/include/2common.h
index 3bb403b..326f891 100644
--- a/firmware/2lib/include/2common.h
+++ b/firmware/2lib/include/2common.h
@@ -151,10 +151,10 @@
  * @param member_data_size	Size of member data in bytes
  * @return VB2_SUCCESS, or non-zero if error.
  */
-int vb2_verify_member_inside(const void *parent, uint32_t parent_size,
-			     const void *member, uint32_t member_size,
-			     uint32_t member_data_offset,
-			     uint32_t member_data_size);
+int vb2_verify_member_inside(const void *parent, size_t parent_size,
+			     const void *member, size_t member_size,
+			     ptrdiff_t member_data_offset,
+			     size_t member_data_size);
 
 /**
  * Verify a signature is fully contained in its parent data
diff --git a/firmware/2lib/include/2return_codes.h b/firmware/2lib/include/2return_codes.h
index 28c0f91..f81dc73 100644
--- a/firmware/2lib/include/2return_codes.h
+++ b/firmware/2lib/include/2return_codes.h
@@ -100,6 +100,32 @@
 	VB2_ERROR_SECDATA_SET_FLAGS,
 
         /**********************************************************************
+	 * Common code errors
+	 */
+	VB2_ERROR_COMMON = VB2_ERROR_BASE + 0x050000,
+
+	/* Buffer is smaller than alignment offset in vb2_align() */
+	VB2_ERROR_ALIGN_BIGGER_THAN_SIZE,
+
+	/* Buffer is smaller than request in vb2_align() */
+	VB2_ERROR_ALIGN_SIZE,
+
+	/* Parent wraps around in vb2_verify_member_inside() */
+	VB2_ERROR_INSIDE_PARENT_WRAPS,
+
+	/* Member wraps around in vb2_verify_member_inside() */
+	VB2_ERROR_INSIDE_MEMBER_WRAPS,
+
+	/* Member outside parent in vb2_verify_member_inside() */
+	VB2_ERROR_INSIDE_MEMBER_OUTSIDE,
+
+	/* Member data wraps around in vb2_verify_member_inside() */
+	VB2_ERROR_INSIDE_DATA_WRAPS,
+
+	/* Member data outside parent in vb2_verify_member_inside() */
+	VB2_ERROR_INSIDE_DATA_OUTSIDE,
+
+        /**********************************************************************
 	 * TODO: errors which must still be made specific
 	 */
 	VB2_ERROR_TODO = VB2_ERROR_BASE + 0xff0000,
diff --git a/tests/vb2_common_tests.c b/tests/vb2_common_tests.c
index fd8a7ac..e476edf 100644
--- a/tests/vb2_common_tests.c
+++ b/tests/vb2_common_tests.c
@@ -23,27 +23,30 @@
 	p0 = (uint8_t *)buf;
 	ptr = p0;
 	size = 16;
-	TEST_EQ(vb2_align(&ptr, &size, 4, 16), 0, "vb2_align() aligned");
+	TEST_SUCC(vb2_align(&ptr, &size, 4, 16), "vb2_align() aligned");
 	TEST_EQ(vb2_offset_of(p0, ptr), 0, "ptr");
 	TEST_EQ(size, 16, "  size");
-	TEST_NEQ(vb2_align(&ptr, &size, 4, 17), 0, "vb2_align() small");
+	TEST_EQ(vb2_align(&ptr, &size, 4, 17),
+		VB2_ERROR_ALIGN_SIZE, "vb2_align() small");
 
 	/* Offset */
 	ptr = p0 + 1;
 	size = 15;
-	TEST_EQ(vb2_align(&ptr, &size, 4, 12), 0, "vb2_align() offset");
+	TEST_SUCC(vb2_align(&ptr, &size, 4, 12), "vb2_align() offset");
 	TEST_EQ(vb2_offset_of(p0, ptr), 4, "ptr");
 	TEST_EQ(size, 12, "  size");
 
 	/* Offset, now too small */
 	ptr = p0 + 1;
 	size = 15;
-	TEST_NEQ(vb2_align(&ptr, &size, 4, 15), 0, "vb2_align() offset small");
+	TEST_EQ(vb2_align(&ptr, &size, 4, 15),
+		VB2_ERROR_ALIGN_SIZE, "vb2_align() offset small");
 
 	/* Offset, too small even to align */
 	ptr = p0 + 1;
 	size = 1;
-	TEST_NEQ(vb2_align(&ptr, &size, 4, 1), 0, "vb2_align() offset tiny");
+	TEST_EQ(vb2_align(&ptr, &size, 4, 1),
+		VB2_ERROR_ALIGN_BIGGER_THAN_SIZE, "vb2_align() offset tiny");
 }
 
 /**
@@ -149,69 +152,79 @@
 
 	{
 		uint8_t *p = (uint8_t *)test_helper_functions;
-		TEST_EQ(vb2_verify_member_inside(p, 20, p, 6, 11, 3), 0,
-			"MemberInside ok 1");
-		TEST_EQ(vb2_verify_member_inside(p, 20, p+4, 4, 8, 4), 0,
-			"MemberInside ok 2");
-		TEST_NEQ(vb2_verify_member_inside(p, 20, p-4, 4, 8, 4), 0,
-			 "MemberInside member before parent");
-		TEST_NEQ(vb2_verify_member_inside(p, 20, p+20, 4, 8, 4), 0,
-			 "MemberInside member after parent");
-		TEST_NEQ(vb2_verify_member_inside(p, 20, p, 21, 0, 0), 0,
-			 "MemberInside member too big");
-		TEST_NEQ(vb2_verify_member_inside(p, 20, p, 4, 21, 0), 0,
-			 "MemberInside data after parent");
-		TEST_NEQ(vb2_verify_member_inside(p, 20, p, 4, UINT32_MAX, 0),
-			 0, "MemberInside data before parent");
-		TEST_NEQ(vb2_verify_member_inside(p, 20, p, 4, 4, 17), 0,
-			 "MemberInside data too big");
-		TEST_NEQ(vb2_verify_member_inside(p, UINT32_MAX,
-						  p+UINT32_MAX-9, 12, 5, 0), 0,
-			 "MemberInside wraparound 1");
-		TEST_NEQ(vb2_verify_member_inside(p, UINT32_MAX,
-						  p+UINT32_MAX-9, 5, 12, 0), 0,
-			 "MemberInside wraparound 2");
-		TEST_NEQ(vb2_verify_member_inside(p, UINT32_MAX,
-						  p+UINT32_MAX-9, 5, 0, 12), 0,
-			 "MemberInside wraparound 3");
+		TEST_SUCC(vb2_verify_member_inside(p, 20, p, 6, 11, 3),
+			  "MemberInside ok 1");
+		TEST_SUCC(vb2_verify_member_inside(p, 20, p+4, 4, 8, 4),
+			  "MemberInside ok 2");
+		TEST_EQ(vb2_verify_member_inside(p, 20, p-4, 4, 8, 4),
+			VB2_ERROR_INSIDE_MEMBER_OUTSIDE,
+			"MemberInside member before parent");
+		TEST_EQ(vb2_verify_member_inside(p, 20, p+20, 4, 8, 4),
+			VB2_ERROR_INSIDE_MEMBER_OUTSIDE,
+			"MemberInside member after parent");
+		TEST_EQ(vb2_verify_member_inside(p, 20, p, 21, 0, 0),
+			VB2_ERROR_INSIDE_MEMBER_OUTSIDE,
+			"MemberInside member too big");
+		TEST_EQ(vb2_verify_member_inside(p, 20, p, 4, 21, 0),
+			VB2_ERROR_INSIDE_DATA_OUTSIDE,
+			"MemberInside data after parent");
+		TEST_EQ(vb2_verify_member_inside(p, 20, p, 4, SIZE_MAX, 0),
+			VB2_ERROR_INSIDE_DATA_OUTSIDE,
+			"MemberInside data before parent");
+		TEST_EQ(vb2_verify_member_inside(p, 20, p, 4, 4, 17),
+			VB2_ERROR_INSIDE_DATA_OUTSIDE,
+			"MemberInside data too big");
+		TEST_EQ(vb2_verify_member_inside(p, -8, p, 12, 0, 0),
+			VB2_ERROR_INSIDE_PARENT_WRAPS,
+			"MemberInside wraparound 1");
+		TEST_EQ(vb2_verify_member_inside(p, 20, p, -8, 0, 0),
+			VB2_ERROR_INSIDE_MEMBER_WRAPS,
+			"MemberInside wraparound 2");
+		TEST_EQ(vb2_verify_member_inside(p, 20, p, 4, 0, -8),
+			VB2_ERROR_INSIDE_DATA_WRAPS,
+			"MemberInside wraparound 3");
 	}
 
 	{
 		struct vb2_packed_key k = {.key_offset = sizeof(k),
 					   .key_size = 128};
-		TEST_EQ(vb2_verify_packed_key_inside(&k, sizeof(k)+128, &k), 0,
-			"PublicKeyInside ok 1");
-		TEST_EQ(vb2_verify_packed_key_inside(&k - 1,
-						     2*sizeof(k)+128, &k),
-			0, "PublicKeyInside ok 2");
-		TEST_NEQ(vb2_verify_packed_key_inside(&k, 128, &k), 0,
-			 "PublicKeyInside key too big");
+		TEST_SUCC(vb2_verify_packed_key_inside(&k, sizeof(k)+128, &k),
+			  "PublicKeyInside ok 1");
+		TEST_SUCC(vb2_verify_packed_key_inside(&k - 1,
+						       2*sizeof(k)+128, &k),
+			  "PublicKeyInside ok 2");
+		TEST_EQ(vb2_verify_packed_key_inside(&k, 128, &k),
+			VB2_ERROR_INSIDE_DATA_OUTSIDE,
+			"PublicKeyInside key too big");
 	}
 
 	{
 		struct vb2_packed_key k = {.key_offset = 100,
 					   .key_size = 4};
-		TEST_NEQ(vb2_verify_packed_key_inside(&k, 99, &k), 0,
-			 "PublicKeyInside offset too big");
+		TEST_EQ(vb2_verify_packed_key_inside(&k, 99, &k),
+			VB2_ERROR_INSIDE_DATA_OUTSIDE,
+			"PublicKeyInside offset too big");
 	}
 
 	{
 		struct vb2_signature s = {.sig_offset = sizeof(s),
 					  .sig_size = 128};
-		TEST_EQ(vb2_verify_signature_inside(&s, sizeof(s)+128, &s), 0,
+		TEST_SUCC(vb2_verify_signature_inside(&s, sizeof(s)+128, &s),
 			"SignatureInside ok 1");
-		TEST_EQ(vb2_verify_signature_inside(&s - 1,
-						    2*sizeof(s)+128, &s),
-			0, "SignatureInside ok 2");
-		TEST_NEQ(vb2_verify_signature_inside(&s, 128, &s), 0,
-			 "SignatureInside sig too big");
+		TEST_SUCC(vb2_verify_signature_inside(&s - 1,
+						      2*sizeof(s)+128, &s),
+			  "SignatureInside ok 2");
+		TEST_EQ(vb2_verify_signature_inside(&s, 128, &s),
+			VB2_ERROR_INSIDE_DATA_OUTSIDE,
+			"SignatureInside sig too big");
 	}
 
 	{
 		struct vb2_signature s = {.sig_offset = 100,
 					  .sig_size = 4};
-		TEST_NEQ(vb2_verify_signature_inside(&s, 99, &s), 0,
-			 "SignatureInside offset too big");
+		TEST_EQ(vb2_verify_signature_inside(&s, 99, &s),
+			VB2_ERROR_INSIDE_DATA_OUTSIDE,
+			"SignatureInside offset too big");
 	}
 }