1 files changed, 6 insertions, 6 deletions
diff --git a/otherlibs/win32unix/unix.ml b/otherlibs/win32unix/unix.ml
index 5231507e1..5bec474e2 100644
--- a/otherlibs/win32unix/unix.ml
+++ b/otherlibs/win32unix/unix.ml
@@ -184,11 +184,11 @@ external unsafe_write : file_descr -> string -> int -> int -> int
                       = "unix_write"
 
 let read fd buf ofs len =
-  if len < 0 || ofs + len > String.length buf
+  if ofs < 0 || len < 0 || ofs > String.length buf - len
   then invalid_arg "Unix.read"
   else unsafe_read fd buf ofs len
 let write fd buf ofs len =
-  if len < 0 || ofs + len > String.length buf
+  if ofs < 0 || len < 0 || ofs > String.length buf - len
   then invalid_arg "Unix.write"
   else unsafe_write fd buf ofs len
 
@@ -549,19 +549,19 @@ external unsafe_sendto :
                                   = "unix_sendto" "unix_sendto_native"
 
 let recv fd buf ofs len flags =
-  if len < 0 || ofs + len > String.length buf
+  if ofs < 0 || len < 0 || ofs > String.length buf - len
   then invalid_arg "Unix.recv"
   else unsafe_recv fd buf ofs len flags
 let recvfrom fd buf ofs len flags =
-  if len < 0 || ofs + len > String.length buf
+  if ofs < 0 || len < 0 || ofs > String.length buf - len
   then invalid_arg "Unix.recvfrom"
   else unsafe_recvfrom fd buf ofs len flags
 let send fd buf ofs len flags =
-  if len < 0 || ofs + len > String.length buf
+  if ofs < 0 || len < 0 || ofs > String.length buf - len
   then invalid_arg "Unix.send"
   else unsafe_send fd buf ofs len flags
 let sendto fd buf ofs len flags addr =
-  if len < 0 || ofs + len > String.length buf
+  if ofs < 0 || len < 0 || ofs > String.length buf - len
   then invalid_arg "Unix.sendto"
   else unsafe_sendto fd buf ofs len flags addr