kconfig/nconf: Fix hang when editing symbol with a long prompt

commit 79e51b5c2deea542b3bb8c66e0d502230b017dde upstream.

Currently it is impossible to edit the value of a config symbol with a
prompt longer than (terminal width - 2) characters.  dialog_inputbox()
calculates a negative x-offset for the input window and newwin() fails
as this is invalid.  It also doesn't check for this failure, so it
busy-loops calling wgetch(NULL) which immediately returns -1.

The additions in the offset calculations also don't match the intended
size of the window.

Limit the window size and calculate the offset similarly to
show_scroll_win().

Fixes: 692d97c380c6 ("kconfig: new configuration interface (nconfig)")
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 11 insertions, 4 deletions

diff --git a/scripts/kconfig/nconf.gui.c b/scripts/kconfig/nconf.gui.c
index 8275f0e55106..4b2f44c20caf 100644
--- a/scripts/kconfig/nconf.gui.c
+++ b/scripts/kconfig/nconf.gui.c
@@ -364,12 +364,14 @@ int dialog_inputbox(WINDOW *main_window,
         WINDOW *prompt_win;
         WINDOW *form_win;
         PANEL *panel;
-        int i, x, y;
+        int i, x, y, lines, columns, win_lines, win_cols;
         int res = -1;
         int cursor_position = strlen(init);
         int cursor_form_win;
         char *result = *resultp;
 
+        getmaxyx(stdscr, lines, columns);
+
         if (strlen(init)+1 > *result_len) {
                 *result_len = strlen(init)+1;
                 *resultp = result = realloc(result, *result_len);
@@ -386,14 +388,19 @@ int dialog_inputbox(WINDOW *main_window,
         if (title)
                 prompt_width = max(prompt_width, strlen(title));
 
+        win_lines = min(prompt_lines+6, lines-2);
+        win_cols = min(prompt_width+7, columns-2);
+        prompt_lines = max(win_lines-6, 0);
+        prompt_width = max(win_cols-7, 0);
+
         /* place dialog in middle of screen */
-        y = (getmaxy(stdscr)-(prompt_lines+4))/2;
-        x = (getmaxx(stdscr)-(prompt_width+4))/2;
+        y = (lines-win_lines)/2;
+        x = (columns-win_cols)/2;
 
         strncpy(result, init, *result_len);
 
         /* create the windows */
-        win = newwin(prompt_lines+6, prompt_width+7, y, x);
+        win = newwin(win_lines, win_cols, y, x);
         prompt_win = derwin(win, prompt_lines+1, prompt_width, 2, 2);
         form_win = derwin(win, 1, prompt_width, prompt_lines+3, 2);
         keypad(form_win, TRUE);