lib: util: Add sys_valid_io_range()

This implements the contraints of
[MS-FSA] 2.1.5.2 Server Requests a Read.

The special handling of [MS-FSA] 2.1.5.3 Server Requests a Write
with offset < 0, should be handled by higher layers!
Which means the check can also be used for writes.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14361

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

1 files changed, 24 insertions, 0 deletions

diff --git a/lib/util/sys_rw.c b/lib/util/sys_rw.c
index 9a6cdcaa606..6fa7ca57365 100644
--- a/lib/util/sys_rw.c
+++ b/lib/util/sys_rw.c
@@ -24,6 +24,30 @@
 #include "system/filesys.h"
 #include "lib/util/sys_rw.h"
 
+bool sys_valid_io_range(off_t offset, size_t length)
+{
+	uint64_t last_byte_ofs;
+
+	if (offset < 0) {
+		return false;
+	}
+
+	if (offset > INT64_MAX) {
+		return false;
+	}
+
+	if (length > UINT32_MAX) {
+		return false;
+	}
+
+	last_byte_ofs = (uint64_t)offset + (uint64_t)length;
+	if (last_byte_ofs > INT64_MAX) {
+		return false;
+	}
+
+	return true;
+}
+
 /*******************************************************************
 A read wrapper that will deal with EINTR/EWOULDBLOCK
 ********************************************************************/