UBUNTU-CVE-2026-97947: Null Pointer Dereference

In the Linux kernel, the following vulnerability has been resolved: x86/amdnode: Fix potential NULL pointer dereference amdsmnread/write() are exported functions around amdsmnrw(), so they are always available even if amdsmninit() fails. In that case, 'amdroots' is NULL and amdsmnrw() will access uninitialized memory. Then, commit: 83518453074d ("x86/amdnode: Add SMN offsets to exclusive region access") added the 'smnexclusive' flag, which indicated the calls to pcirequestconfigregionexclusive() succeeded, to prevent concurrent userspace access. Commit: 0a4b61d9c2e4 ("x86/amdnode: Fix AMD root device caching") re-ordered initialization so pcirequestconfigregionexclusive() is called earlier and a failure exits amdsmninit() before allocating 'amdroots'. The setting of 'smnexclusive' moved to the end of amdsmninit(), after 'amdroots' is allocated. It became redundant and can be removed. Replace 'smnexclusive' with directly checking 'amdroots', to fix a potential NULL pointer dereference and to simplify the logic. [ bp: Reorg commit message, touchup comment. ] [ mingo: Rebase & further touchups. ]