[vlc-devel] [PATCH] control/globalhotkeys: xcb: fix p_sys->p_map population
filip at atch.se
Mon Mar 20 13:38:18 CET 2017
*Hugo Beauzée-Luyssen* just pointed out that the commit message in the
patch which this email is a reply to contains an extremely weird typo.
The first sentence is supposed to read *"As described in **#18836**,
[...]"*, not *"#17747"* (which isn't even remotely related to what
this patch is set out to address).
The patch has now been applied with the typo fixed, but I deeply
apologize for any confusion that it may have caused.
On 2017-03-18 18:00, Filip Roséen wrote:
> 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.
> fixes: #18136
> 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.
> Best Regards,\
> Filip RosÃ©en
> 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
> --- a/modules/control/globalhotkeys/xcb.c
> +++ b/modules/control/globalhotkeys/xcb.c
> @@ -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 )
> - continue;
> 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 )
> + break;
> 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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