[vlc-devel] [PATCH] control/globalhotkeys: xcb: fix p_sys->p_map population
filip at atch.se
Sat Mar 18 18:00:33 CET 2017
As described in #17747, certain configurations end up causing a
double-free in xcb.c:Close due to the same value returned from
xcb_key_symbols_get_keycode appearing multiple times in p_sys->p_map.
The code responsible for clean-up assumes that every value refers to a
separate allocated resource, whereas Mapping potentially populates
p_sys->p_map with the same value several times.
These changes make sure that initialization vs clean-up is in harmony.
A side-effect of these changes is that the we are allocating more
resources than before. There are two alternative fixes (each suffering
from added code complexity):
1. store all return-values xcb_key_symbols_get_keycode in a separate
array (with unique entries), so that clean-up can use this array
instead of looping through p_sys->p_map.
2. As duplicate entries in p_sys->p_map in terms of ->p_keys are
guaranteed to be seqential, one could also update the clean-up loop
so that it does not free the about-to-be-freed value if it compares
equal to the previous item.
It is important to note that xcb_keysym_t is (at least currently)
typedef'd to "uint8_t", meaning that even though we in theory allocate
3 times more memory at the affected code-path - the real impact on
memory usage is very small.
modules/control/globalhotkeys/xcb.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/modules/control/globalhotkeys/xcb.c b/modules/control/globalhotkeys/xcb.c
index 42fb9f4854..f083b81336 100644
@@ -308,11 +308,6 @@ static bool Mapping( intf_thread_t *p_intf )
if( i_vlc_key == KEY_UNSET )
- xcb_keycode_t *p_keys = xcb_key_symbols_get_keycode(
- p_sys->p_symbols, GetX11Key( i_vlc_key & ~KEY_MODIFIER ) );
- if( !p_keys )
const unsigned i_modifier = GetX11Modifier( p_sys->p_connection,
p_sys->p_symbols, i_vlc_key & KEY_MODIFIER );
@@ -325,6 +320,12 @@ static bool Mapping( intf_thread_t *p_intf )
if( i != 0 && i_ignored == 0)
+ xcb_keycode_t *p_keys = xcb_key_symbols_get_keycode(
+ p_sys->p_symbols, GetX11Key( i_vlc_key & ~KEY_MODIFIER ) );
+ if( !p_keys )
hotkey_mapping_t *p_map = realloc( p_sys->p_map,
sizeof(*p_sys->p_map) * (p_sys->i_map+1) );
if( !p_map )
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