[Mesa-dev] [Mesa-stable] [PATCH v2] glx: Properly handle cases where screen creation fails

[Emil Velikov]

On 22 February 2018 at 14:33, Chuck Atkins <chuck.atkins at kitware.com> wrote:
> This fixes a segfault exposed by a29d63ecf7 which occurs when swr is
> used on an unsupported architecture.
>
> v2: re-work to place logic in xmesa_init_display
>
> Signed-off-by: Chuck Atkins <chuck.atkins at kitware.com>
> Cc: mesa-stable at lists.freedesktop.org
> Cc: George Kyriazis <george.kyriazis at intel.com>
> Cc: Bruce Cherniak <bruce.cherniak at intel.com>
FWIW
Reviewed-by: Emil Velikov <emil.l.velikov at gmail.com>

> ---
>  src/gallium/state_trackers/glx/xlib/glx_api.c |  5 ++-
>  src/gallium/state_trackers/glx/xlib/xm_api.c  | 56 +++++++++++++--------------
>  src/gallium/state_trackers/glx/xlib/xm_api.h  |  2 +-
>  3 files changed, 33 insertions(+), 30 deletions(-)
>
> diff --git a/src/gallium/state_trackers/glx/xlib/glx_api.c b/src/gallium/state_trackers/glx/xlib/glx_api.c
> index 1994e6823a..6ec3a31d5f 100644
> --- a/src/gallium/state_trackers/glx/xlib/glx_api.c
> +++ b/src/gallium/state_trackers/glx/xlib/glx_api.c
> @@ -743,7 +743,10 @@ choose_visual( Display *dpy, int screen, const int *list, GLboolean fbConfig )
>     int numAux = 0;
>     GLint num_samples = 0;
>
> -   xmesa_init( dpy );
> +   if (xmesa_init( dpy ) != 0) {
> +      _mesa_warning(NULL, "Failed to initialize display");
> +      return NULL;
> +   }
>
>     parselist = list;
>
> diff --git a/src/gallium/state_trackers/glx/xlib/xm_api.c b/src/gallium/state_trackers/glx/xlib/xm_api.c
> index 934c0aba11..e8cbb618ce 100644
> --- a/src/gallium/state_trackers/glx/xlib/xm_api.c
> +++ b/src/gallium/state_trackers/glx/xlib/xm_api.c
> @@ -142,8 +142,11 @@ xmesa_close_display(Display *display)
>  {
>     XMesaExtDisplayInfo *info, *prev;
>
> +   /* These assertions are not valid since screen creation can fail and result
> +    * in an empty list
>     assert(MesaExtInfo.ndisplays > 0);
>     assert(MesaExtInfo.head);
> +   */
>
Gut feeling suggests that this and perhaps the choose_visual() hunks
are signs of other preexisting bugs.
If you decide to stick around with xlib-glx it is worth nuking the
XMesa abstraction/API.

It hasn't been used in ages, it will help you simplify the whole thing
and squash a lot more lurking bugs.

HTH
Emil