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, 80 insertions, 0 deletions

diff --git a/rust/zerocopy-derive/derive/unaligned.rs b/rust/zerocopy-derive/derive/unaligned.rs
new file mode 100644
index 000000000..7c97d62e2
--- /dev/null
+++ b/rust/zerocopy-derive/derive/unaligned.rs
@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: (BSD-2-Clause OR Apache-2.0) OR MIT
+//
+use proc_macro2::{Span, TokenStream};
+use syn::{Data, DataEnum, DataStruct, DataUnion, Error};
+
+use crate::{
+    repr::{EnumRepr, StructUnionRepr},
+    util::{Ctx, FieldBounds, ImplBlockBuilder, Trait},
+};
+
+pub(crate) fn derive_unaligned(ctx: &Ctx, _top_level: Trait) -> Result<TokenStream, Error> {
+    match &ctx.ast.data {
+        Data::Struct(strct) => derive_unaligned_struct(ctx, strct),
+        Data::Enum(enm) => derive_unaligned_enum(ctx, enm),
+        Data::Union(unn) => derive_unaligned_union(ctx, unn),
+    }
+}
+
+/// A struct is `Unaligned` if:
+/// - `repr(align)` is no more than 1 and either
+///   - `repr(C)` or `repr(transparent)` and
+///     - all fields `Unaligned`
+///   - `repr(packed)`
+fn derive_unaligned_struct(ctx: &Ctx, strct: &DataStruct) -> Result<TokenStream, Error> {
+    let repr = StructUnionRepr::from_attrs(&ctx.ast.attrs)?;
+    repr.unaligned_validate_no_align_gt_1()?;
+
+    let field_bounds = if repr.is_packed_1() {
+        FieldBounds::None
+    } else if repr.is_c() || repr.is_transparent() {
+        FieldBounds::ALL_SELF
+    } else {
+        return ctx.error_or_skip(Error::new(
+            Span::call_site(),
+            "must have #[repr(C)], #[repr(transparent)], or #[repr(packed)] attribute in order to guarantee this type's alignment",
+        ));
+    };
+
+    Ok(ImplBlockBuilder::new(ctx, strct, Trait::Unaligned, field_bounds).build())
+}
+
+/// An enum is `Unaligned` if:
+/// - No `repr(align(N > 1))`
+/// - `repr(u8)` or `repr(i8)`
+fn derive_unaligned_enum(ctx: &Ctx, enm: &DataEnum) -> Result<TokenStream, Error> {
+    let repr = EnumRepr::from_attrs(&ctx.ast.attrs)?;
+    repr.unaligned_validate_no_align_gt_1()?;
+
+    if !repr.is_u8() && !repr.is_i8() {
+        return ctx.error_or_skip(Error::new(
+            Span::call_site(),
+            "must have #[repr(u8)] or #[repr(i8)] attribute in order to guarantee this type's alignment",
+        ));
+    }
+
+    Ok(ImplBlockBuilder::new(ctx, enm, Trait::Unaligned, FieldBounds::ALL_SELF).build())
+}
+
+/// Like structs, a union is `Unaligned` if:
+/// - `repr(align)` is no more than 1 and either
+///   - `repr(C)` or `repr(transparent)` and
+///     - all fields `Unaligned`
+///   - `repr(packed)`
+fn derive_unaligned_union(ctx: &Ctx, unn: &DataUnion) -> Result<TokenStream, Error> {
+    let repr = StructUnionRepr::from_attrs(&ctx.ast.attrs)?;
+    repr.unaligned_validate_no_align_gt_1()?;
+
+    let field_type_trait_bounds = if repr.is_packed_1() {
+        FieldBounds::None
+    } else if repr.is_c() || repr.is_transparent() {
+        FieldBounds::ALL_SELF
+    } else {
+        return ctx.error_or_skip(Error::new(
+            Span::call_site(),
+            "must have #[repr(C)], #[repr(transparent)], or #[repr(packed)] attribute in order to guarantee this type's alignment",
+        ));
+    };
+
+    Ok(ImplBlockBuilder::new(ctx, unn, Trait::Unaligned, field_type_trait_bounds).build())
+}