x86/amd_node: Prevent 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 smn_exclusive 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.
Setting 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 avoid a potential
NULL pointer dereference.

  [ bp: Reorg commit message, touchup comment. ]

Fixes: 77466b798d59 ("x86/amd_node: Remove dependency on AMD_NB")
Signed-off-by: Jason Andryuk <jason.andryuk@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260825214805.39148-3-jason.andryuk@amd.com

0 files changed, 0 insertions, 0 deletions