Invalid free in cairo_ft_apply_variations

[Michael Catanzaro <mcatanzaro () igalia com>]

Hi,

cairo 1.16.0, in cairo_ft_apply_variations() in cairo-ft-font.c frees 
memory using the wrong free function, leading to memory corruption. 
Because cairo is used by WebKitGTK+, WPE WebKit, and the WinCairo port 
of WebKit, this issue can be triggered by web content. CVE-2018-19876 
has been allocated by MITRE. For details, see:

https://gitlab.freedesktop.org/cairo/cairo/merge_requests/5

We recommend Linux distros should patch cairo because the fix has not 
yet been integrated into the upstream source code repository:

https://gitlab.freedesktop.org/cairo/cairo/merge_requests/5.patch
(warning: link provided for convenience, it is not a stable link)

Michael