[Xcb] [PATCH util-keysymy] Fix handling of error connections

[Uli Schlachter]

On 16.11.2013 12:33, Uli Schlachter wrote:
> When an xcb_connection_t goes into an error state, all operations on it will
> fail. This means that after a call to xcb_key_symbols_get_reply(), syms->u.reply
> would still be a NULL pointer and that xcb_get_setup() returns a NULL pointer.
> 
> The only way for xcb_get_setup() to return NULL is for an error connection, but
> xcb_get_keyboard_mapping_reply() could also fail for other reasons. So to fix
> this, all functions need to check for error connections and if syms->u.reply is
> not NULL.
> 
> This was tested with the following C code:
> 
>   #include <xcb_keysyms.h>
>   #include <stdio.h>
>   #include <stdlib.h>
> 
>   int main()
>   {
>   	xcb_connection_t *c = xcb_connect(NULL, NULL);
>   	xcb_key_symbols_t *syms = xcb_key_symbols_alloc(c);
>   	/* The above sent a GetKeyboardMapping request. Let's now break the
>   	 * connection so that it cannot get the reply.
>   	 */
>   	uint32_t max = xcb_get_maximum_request_length(c);
>   	xcb_screen_t *s = xcb_setup_roots_iterator(xcb_get_setup(c)).data;
>   	size_t len = (max << 2) * 2;
>   	void *p = malloc(len);
> 
>   	printf("Sending request of length %d*2=%d\n",
>   			xcb_get_maximum_request_length(c), len);
>   	xcb_change_property(c, XCB_PROP_MODE_REPLACE, s->root,
>   			XCB_ATOM_STRING, XCB_ATOM_STRING, 8, len, p);
>   	free(p);
> 
>   	if (!xcb_connection_has_error(c))
>   		puts("Connection did not break :(");
> 
>   	/* Crash? */
>   	free(xcb_key_symbols_get_keycode(syms, 0xff14));
> 
>   	return 0;
>   }
> 
> Reference: https://awesome.naquadah.org/bugs/index.php?do=details&task_id=1195
> Signed-off-by: Uli Schlachter <psychon at znc.in>

Merged.

> ---
>  keysyms/keysyms.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/keysyms/keysyms.c b/keysyms/keysyms.c
> index daa863f..419c58b 100644
> --- a/keysyms/keysyms.c
> +++ b/keysyms/keysyms.c
> @@ -77,7 +77,7 @@ xcb_key_symbols_alloc (xcb_connection_t *c)
>    xcb_keycode_t     min_keycode;
>    xcb_keycode_t     max_keycode;
> 
> -  if (!c)
> +  if (!c || xcb_connection_has_error(c))
>      return NULL;
> 
>    syms = malloc (sizeof (xcb_key_symbols_t));
> @@ -198,10 +198,13 @@ xcb_keysym_t xcb_key_symbols_get_keysym (xcb_key_symbols_t
> *syms,
>    xcb_keycode_t max_keycode;
>    int        per;
> 
> -  if (!syms)
> +  if (!syms || xcb_connection_has_error(syms->c))
>      return keysym_null;
> 
>    xcb_key_symbols_get_reply (syms, NULL);
> +
> +  if (!syms->u.reply)
> +    return keysym_null;
> 
>    keysyms = xcb_get_keyboard_mapping_keysyms (syms->u.reply);
>    min_keycode = xcb_get_setup (syms->c)->min_keycode;
> @@ -245,12 +248,15 @@ xcb_key_symbols_get_keycode(xcb_key_symbols_t *syms,
>    int j, nresult = 0;
>    xcb_keycode_t i, min, max, *result = NULL, *result_np = NULL;
> 
> -  if(syms)
> +  if(syms && !xcb_connection_has_error(syms->c))
>    {
>        xcb_key_symbols_get_reply (syms, NULL);
>        min = xcb_get_setup(syms->c)->min_keycode;
>        max = xcb_get_setup(syms->c)->max_keycode;
> 
> +      if (!syms->u.reply)
> +        return NULL;
> +
>        for(i = min; i && i <= max; i++)
>            for(j = 0; j < syms->u.reply->keysyms_per_keycode; j++)
>            {
> @@ -298,7 +304,7 @@ int
>  xcb_refresh_keyboard_mapping (xcb_key_symbols_t         *syms,
>  			   xcb_mapping_notify_event_t *event)
>  {
> -  if (event->request == XCB_MAPPING_KEYBOARD && syms) {
> +  if (event->request == XCB_MAPPING_KEYBOARD && syms &&
> !xcb_connection_has_error(syms->c)) {
>      if (syms->tag == TAG_VALUE) {
>        xcb_keycode_t     min_keycode;
>        xcb_keycode_t     max_keycode;
> 


-- 
<alanc> I think someone had a Xprint version of glxgears at one point,
    but benchmarking how many GL pages you can print per second
    was deemed too silly to merge