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, 136 insertions, 0 deletions

diff --git a/rust/zerocopy-derive/derive/mod.rs b/rust/zerocopy-derive/derive/mod.rs
new file mode 100644
index 000000000..b3839fcf7
--- /dev/null
+++ b/rust/zerocopy-derive/derive/mod.rs
@@ -0,0 +1,136 @@
+// SPDX-License-Identifier: (BSD-2-Clause OR Apache-2.0) OR MIT
+//
+pub mod from_bytes;
+pub mod into_bytes;
+pub mod known_layout;
+pub mod try_from_bytes;
+pub mod unaligned;
+
+use proc_macro2::{Span, TokenStream};
+use quote::quote;
+use syn::{Data, Error};
+
+use crate::{
+    repr::StructUnionRepr,
+    util::{Ctx, DataExt, FieldBounds, ImplBlockBuilder, Trait},
+};
+
+pub(crate) fn derive_immutable(ctx: &Ctx, _top_level: Trait) -> Result<TokenStream, Error> {
+    Ok(match &ctx.ast.data {
+        Data::Struct(strct) => {
+            ImplBlockBuilder::new(ctx, strct, Trait::Immutable, FieldBounds::ALL_SELF).build()
+        }
+        Data::Enum(enm) => {
+            ImplBlockBuilder::new(ctx, enm, Trait::Immutable, FieldBounds::ALL_SELF).build()
+        }
+        Data::Union(unn) => {
+            ImplBlockBuilder::new(ctx, unn, Trait::Immutable, FieldBounds::ALL_SELF).build()
+        }
+    })
+}
+
+pub(crate) fn derive_hash(ctx: &Ctx, _top_level: Trait) -> Result<TokenStream, Error> {
+    // This doesn't delegate to `impl_block` because `impl_block` assumes it is
+    // deriving a `zerocopy`-defined trait, and these trait impls share a common
+    // shape that `Hash` does not. In particular, `zerocopy` traits contain a
+    // method that only `zerocopy_derive` macros are supposed to implement, and
+    // `impl_block` generating this trait method is incompatible with `Hash`.
+    let type_ident = &ctx.ast.ident;
+    let (impl_generics, ty_generics, where_clause) = ctx.ast.generics.split_for_impl();
+    let where_predicates = where_clause.map(|clause| &clause.predicates);
+    let zerocopy_crate = &ctx.zerocopy_crate;
+    let core = ctx.core_path();
+    Ok(quote! {
+        impl #impl_generics #core::hash::Hash for #type_ident #ty_generics
+        where
+            Self: #zerocopy_crate::IntoBytes + #zerocopy_crate::Immutable,
+            #where_predicates
+        {
+            fn hash<H: #core::hash::Hasher>(&self, state: &mut H) {
+                #core::hash::Hasher::write(state, #zerocopy_crate::IntoBytes::as_bytes(self))
+            }
+
+            fn hash_slice<H: #core::hash::Hasher>(data: &[Self], state: &mut H) {
+                #core::hash::Hasher::write(state, #zerocopy_crate::IntoBytes::as_bytes(data))
+            }
+        }
+    })
+}
+
+pub(crate) fn derive_eq(ctx: &Ctx, _top_level: Trait) -> Result<TokenStream, Error> {
+    // This doesn't delegate to `impl_block` because `impl_block` assumes it is
+    // deriving a `zerocopy`-defined trait, and these trait impls share a common
+    // shape that `Eq` does not. In particular, `zerocopy` traits contain a
+    // method that only `zerocopy_derive` macros are supposed to implement, and
+    // `impl_block` generating this trait method is incompatible with `Eq`.
+    let type_ident = &ctx.ast.ident;
+    let (impl_generics, ty_generics, where_clause) = ctx.ast.generics.split_for_impl();
+    let where_predicates = where_clause.map(|clause| &clause.predicates);
+    let zerocopy_crate = &ctx.zerocopy_crate;
+    let core = ctx.core_path();
+    Ok(quote! {
+        impl #impl_generics #core::cmp::PartialEq for #type_ident #ty_generics
+        where
+            Self: #zerocopy_crate::IntoBytes + #zerocopy_crate::Immutable,
+            #where_predicates
+        {
+            fn eq(&self, other: &Self) -> bool {
+                #core::cmp::PartialEq::eq(
+                    #zerocopy_crate::IntoBytes::as_bytes(self),
+                    #zerocopy_crate::IntoBytes::as_bytes(other),
+                )
+            }
+        }
+
+        impl #impl_generics #core::cmp::Eq for #type_ident #ty_generics
+        where
+            Self: #zerocopy_crate::IntoBytes + #zerocopy_crate::Immutable,
+            #where_predicates
+        {
+        }
+    })
+}
+
+pub(crate) fn derive_split_at(ctx: &Ctx, _top_level: Trait) -> Result<TokenStream, Error> {
+    let repr = StructUnionRepr::from_attrs(&ctx.ast.attrs)?;
+
+    match &ctx.ast.data {
+        Data::Struct(_) => {}
+        Data::Enum(_) | Data::Union(_) => {
+            return ctx
+                .error_or_skip(Error::new(Span::call_site(), "can only be applied to structs"));
+        }
+    };
+
+    if repr.get_packed().is_some() {
+        return ctx.error_or_skip(Error::new(
+            Span::call_site(),
+            "must not have #[repr(packed)] attribute",
+        ));
+    }
+
+    if !(repr.is_c() || repr.is_transparent()) {
+        return ctx.error_or_skip(Error::new(
+            Span::call_site(),
+            "must have #[repr(C)] or #[repr(transparent)] in order to guarantee this type's layout is splitable",
+        ));
+    }
+
+    let fields = ctx.ast.data.fields();
+    let trailing_field = if let Some(((_, _, trailing_field), _)) = fields.split_last() {
+        trailing_field
+    } else {
+        return ctx.error_or_skip(Error::new(Span::call_site(), "must at least one field"));
+    };
+
+    let zerocopy_crate = &ctx.zerocopy_crate;
+    // SAFETY: `#ty`, per the above checks, is `repr(C)` or `repr(transparent)`
+    // and is not packed; its trailing field is guaranteed to be well-aligned
+    // for its type. By invariant on `FieldBounds::TRAILING_SELF`, the trailing
+    // slice of the trailing field is also well-aligned for its type.
+    Ok(ImplBlockBuilder::new(ctx, &ctx.ast.data, Trait::SplitAt, FieldBounds::TRAILING_SELF)
+        .inner_extras(quote! {
+            type Elem = <#trailing_field as #zerocopy_crate::SplitAt>::Elem;
+        })
+        .build())
+}