CVE-2026-97947

In the Linux kernel, the following vulnerability has been resolved:

x86/amd node: Fix potential NULL pointer dereference

amd smn read/write() are exported functions around amd smn rw(), so they are always available even if amd smn init() fails. In that case, 'amd roots' is NULL and amd smn rw() will access uninitialized memory.

Then, commit:

83518453074d ("x86/amd node: Add SMN offsets to exclusive region access")

added the 'smn exclusive' flag, which indicated the calls to pci request config region exclusive() succeeded, to prevent concurrent userspace access.

Commit:

0a4b61d9c2e4 ("x86/amd node: Fix AMD root device caching")

re-ordered initialization so pci request config region exclusive() is called earlier and a failure exits amd smn init() before allocating 'amd roots'. The setting of 'smn exclusive' moved to the end of amd smn init(), after 'amd roots' is allocated. It became redundant and can be removed.

Replace 'smn exclusive' with directly checking 'amd roots', to fix a potential NULL pointer dereference and to simplify the logic.

[ bp: Reorg commit message, touchup comment. ] [ mingo: Rebase & further touchups. ]