[BUG] readline history

[Alexander Aring]

Hi,

the issues is that hist_prev or hist_next runs:
"list_entry(history_current->next, struct history, list);"

on an empty list with no entries and history->line is a dangling pointer.

because the list head don't include a char *line and on an empty list
the attributes are prev == next.

I hacked a solution which check on an empty list at first and returning
NULL.

diff --git a/lib/readline.c b/lib/readline.c
index b70bca8..0892cf5 100644
--- a/lib/readline.c
+++ b/lib/readline.c
@@ -67,6 +67,9 @@ static const char *hist_prev(void)
 {
        struct history *history;
 
+       if (list_empty(&history_list))
+               return NULL;
+
        if (history_current->prev == &history_list) {
                history = list_entry(history_current, struct history, list);
                getcmd_cbeep();
@@ -84,6 +87,9 @@ static const char *hist_next(void)
 {
        struct history *history;
 
+       if (list_empty(&history_list))
+               return NULL;
+
        if (history_current->next == &history_list) {
                history_current = &history_list;
                return "";
@@ -301,6 +307,9 @@ int readline(const char *prompt, char *buf, int len)
                        else
                                hline = hist_next();
 
+                       if (!hline)
+                               break;
+
                        /* nuke the current line */
                        /* first, go home */
                        BEGINNING_OF_LINE();

Don't know if it should make a beep or not, just hacked not complete tested.
Maybe there are similar issues in other functions.

- Alex