glx: Don't create a shared context if the other context isn't the same kind
Each of the DRI, DRI2, and DRISW backends contain code like the following in their create-context routine: if (shareList) { pcp_shared = (struct dri2_context *) shareList; shared = pcp_shared->driContext; } This assumes that the glx_context *shareList is actually the correct derived type. However, if shareList was created as an indirect-rendering context, it will not be the expected type. As a result, shared will contain garbage. This garbage will be passed to the driver, and the driver will probably segfault. This can be observed with the following GLX code: ctx0 = glXCreateContext(dpy, visinfo, NULL, False); ctx1 = glXCreateContext(dpy, visinfo, ctx0, True); Create-context is the only case where this occurs. All other cases where a context is passed to the backend, it is the 'this' pointer (i.e., we got to the backend by call something from ctx->vtable). To work around this, check that the shareList->vtable->destroy method is the same as the destroy method of the expected type. We could also check that shareList->vtable matches the vtable or by adding a "tag" to glx_context to identify the derived type. NOTE: This is a candidate for the 7.11 branch. Signed-off-by: Ian Romanick <ian.d.romanick@intel.com> Reviewed-by: Adam Jackson <ajax@redhat.com> Reviewed-by: Eric Anholt <eric@anholt.net>
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@ -185,6 +185,13 @@ dri2_create_context(struct glx_screen *base,
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__DRIcontext *shared = NULL;
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if (shareList) {
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/* If the shareList context is not a DRI2 context, we cannot possibly
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* create a DRI2 context that shares it.
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*/
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if (shareList->vtable->destroy != dri2_destroy_context) {
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return NULL;
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}
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pcp_shared = (struct dri2_context *) shareList;
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shared = pcp_shared->driContext;
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}
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@ -587,6 +587,13 @@ dri_create_context(struct glx_screen *base,
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return NULL;
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if (shareList) {
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/* If the shareList context is not a DRI context, we cannot possibly
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* create a DRI context that shares it.
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*/
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if (shareList->vtable->destroy != dri_destroy_context) {
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return NULL;
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}
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pcp_shared = (struct dri_context *) shareList;
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shared = pcp_shared->driContext;
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}
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@ -383,6 +383,13 @@ drisw_create_context(struct glx_screen *base,
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return NULL;
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if (shareList) {
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/* If the shareList context is not a DRISW context, we cannot possibly
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* create a DRISW context that shares it.
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*/
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if (shareList->vtable->destroy != drisw_destroy_context) {
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return NULL;
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}
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pcp_shared = (struct drisw_context *) shareList;
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shared = pcp_shared->driContext;
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}
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