In the Linux kernel, the following vulnerability has been resolved: drm/dpmst: Ensure mstprimary pointer is valid in drmdpmsthandleupreq() While receiving an MST up request message from one thread in drmdpmsthandleupreq(), the MST topology could be removed from another thread via drmdpmsttopologymgrsetmst(false), freeing mstprimary and setting drmdpmsttopologymgr::mstprimary to NULL. This could lead to a NULL deref/use-after-free of mstprimary in drmdpmsthandleupreq(). Avoid the above by holding a reference for mstprimary in drmdpmsthandleupreq() while it's used. v2: Fix kfreeing the request if getting an mst_primary reference fails.