linux-user: check fd is >= 0 in fd_trans_host_to_target_data/fd_trans…

…_host_to_target_addr

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Riku Voipio <riku.voipio@linaro.org>

linux-user/syscall.c

@@ -309,15 +309,15 @@ static unsigned int target_fd_max;
 
 static TargetFdDataFunc fd_trans_host_to_target_data(int fd)
 {
-    if (fd < target_fd_max && target_fd_trans[fd]) {
+    if (fd >= 0 && fd < target_fd_max && target_fd_trans[fd]) {
         return target_fd_trans[fd]->host_to_target_data;
     }
     return NULL;
 }
 
 static TargetFdAddrFunc fd_trans_target_to_host_addr(int fd)
 {
-    if (fd < target_fd_max && target_fd_trans[fd]) {
+    if (fd >= 0 && fd < target_fd_max && target_fd_trans[fd]) {
         return target_fd_trans[fd]->target_to_host_addr;
     }
     return NULL;