x86/amd_node: Fix PCI device reference counting in amd_smn_init()grafted

The local "root" pointer is a temporary variable used during the device
search. Therefore, refcount related to the search iterators should be cleaned
up after the search is complete.

Use the __free() cleanup macro to ensure the refcount is decremented when the
temporary pointer goes out of scope.

Additionally, increment the refcount when caching a root pointer. This ensures
the in-use refcount is separate from the temporary search refcounting.

Finally, drop the redundant "root = NULL" before the second search loop. The
pci_get_class() iterator always decrements the refcount of its "from"
argument, so the first loop can only fall through with "root" already NULL.

Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: LLM
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com

1 files changed, 52 insertions, 0 deletions

diff --git a/rust/quote/spanned.rs b/rust/quote/spanned.rs
new file mode 100644
index 000000000..54ce9177f
--- /dev/null
+++ b/rust/quote/spanned.rs
@@ -0,0 +1,52 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use crate::ToTokens;
+use proc_macro2::extra::DelimSpan;
+use proc_macro2::{Span, TokenStream};
+
+// Not public API other than via the syn crate. Use syn::spanned::Spanned.
+pub trait Spanned: private::Sealed {
+    fn __span(&self) -> Span;
+}
+
+impl Spanned for Span {
+    fn __span(&self) -> Span {
+        *self
+    }
+}
+
+impl Spanned for DelimSpan {
+    fn __span(&self) -> Span {
+        self.join()
+    }
+}
+
+impl<T: ?Sized + ToTokens> Spanned for T {
+    fn __span(&self) -> Span {
+        join_spans(self.into_token_stream())
+    }
+}
+
+fn join_spans(tokens: TokenStream) -> Span {
+    let mut iter = tokens.into_iter().map(|tt| tt.span());
+
+    let first = match iter.next() {
+        Some(span) => span,
+        None => return Span::call_site(),
+    };
+
+    iter.fold(None, |_prev, next| Some(next))
+        .and_then(|last| first.join(last))
+        .unwrap_or(first)
+}
+
+mod private {
+    use crate::ToTokens;
+    use proc_macro2::extra::DelimSpan;
+    use proc_macro2::Span;
+
+    pub trait Sealed {}
+    impl Sealed for Span {}
+    impl Sealed for DelimSpan {}
+    impl<T: ?Sized + ToTokens> Sealed for T {}
+}