Commit f180b04d authored by
glx: Fix SEGV due to dereferencing a NULL ptr from XCB-GLX.
When run in optirun, applications that linked to `libGLX.so` and then proceeded to querying Mesa for extension strings caused a SEGV in Mesa. `glXQueryExtensionsString` was calling a chain of functions that eventually led to `__glXQueryServerString`. This function would call `xcb_glx_query_server_string` then `xcb_glx_query_server_string_reply`. The latter for some unknown reason returned `NULL`. Passing this `NULL` to `xcb_glx_query_server_string_string_length` would cause a SEGV as the function tried to dereference it. The reason behind the function returning `NULL` is yet to be determined, however, simply checking that the ptr is not `NULL` resolves this. A similar check has been added to `__glXGetString` for completeness sake, although not immediately necessary. In addition to that, we stumbled into a similar problem in `AllocAndFetchScreenConfigs` which tries to access the configs to free them if `__glXQueryServerString` fails. This, of course, SEGVs, because the configs are yet to have been allocated. Simply continuing past the configs if their config ptrs are `NULL` resolves this. We also switch to `calloc` to make sure that the config ptrs are `NULL` by default, and not some uninitialized value. Cc: email@example.com Fixes: 24b8a8cf "glx: implement __glXGetString, hide __glXGetStringFromServer" Fixes: cb3610e3 "Import the GLX client side library, formerly from xc/lib/GL/glx. Build it " Reviewed-by: Adam Jackson <firstname.lastname@example.org> Signed-off-by: Hal Gentz <email@example.com> (cherry picked from commit 1591d1fe)
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