fix shell msh_exec memory over-bound.
@@ -374,7 +374,7 @@ int msh_exec(char *cmd, rt_size_t length)
int cmd_ret;
/* strim the beginning of command */
- while (*cmd == ' ' || *cmd == '\t')
+ while ((length > 0) && (*cmd == ' ' || *cmd == '\t'))
{
cmd++;
length--;
