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, 198 insertions, 0 deletions

diff --git a/scripts/elf-parse.c b/scripts/elf-parse.c
new file mode 100644
index 000000000..99869ff91
--- /dev/null
+++ b/scripts/elf-parse.c
@@ -0,0 +1,198 @@
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include "elf-parse.h"
+
+struct elf_funcs elf_parser;
+
+/*
+ * Get the whole file as a programming convenience in order to avoid
+ * malloc+lseek+read+free of many pieces.  If successful, then mmap
+ * avoids copying unused pieces; else just read the whole file.
+ * Open for both read and write.
+ */
+static void *map_file(char const *fname, size_t *size)
+{
+	int fd;
+	struct stat sb;
+	void *addr = NULL;
+
+	fd = open(fname, O_RDWR);
+	if (fd < 0) {
+		perror(fname);
+		return NULL;
+	}
+	if (fstat(fd, &sb) < 0) {
+		perror(fname);
+		goto out;
+	}
+	if (!S_ISREG(sb.st_mode)) {
+		fprintf(stderr, "not a regular file: %s\n", fname);
+		goto out;
+	}
+
+	addr = mmap(0, sb.st_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
+	if (addr == MAP_FAILED) {
+		fprintf(stderr, "Could not mmap file: %s\n", fname);
+		goto out;
+	}
+
+	*size = sb.st_size;
+
+out:
+	close(fd);
+	return addr;
+}
+
+static int elf_parse(const char *fname, void *addr, uint32_t types)
+{
+	Elf_Ehdr *ehdr = addr;
+	uint16_t type;
+
+	switch (ehdr->e32.e_ident[EI_DATA]) {
+	case ELFDATA2LSB:
+		elf_parser.r	= rle;
+		elf_parser.r2	= r2le;
+		elf_parser.r8	= r8le;
+		elf_parser.w	= wle;
+		elf_parser.w8	= w8le;
+		break;
+	case ELFDATA2MSB:
+		elf_parser.r	= rbe;
+		elf_parser.r2	= r2be;
+		elf_parser.r8	= r8be;
+		elf_parser.w	= wbe;
+		elf_parser.w8	= w8be;
+		break;
+	default:
+		fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
+			ehdr->e32.e_ident[EI_DATA], fname);
+		return -1;
+	}
+
+	if (memcmp(ELFMAG, ehdr->e32.e_ident, SELFMAG) != 0 ||
+	    ehdr->e32.e_ident[EI_VERSION] != EV_CURRENT) {
+		fprintf(stderr, "unrecognized ELF file %s\n", fname);
+		return -1;
+	}
+
+	type = elf_parser.r2(&ehdr->e32.e_type);
+	if (!((1 << type) & types)) {
+		fprintf(stderr, "Invalid ELF type file %s\n", fname);
+		return -1;
+	}
+
+	switch (ehdr->e32.e_ident[EI_CLASS]) {
+	case ELFCLASS32: {
+		elf_parser.ehdr_shoff		= ehdr32_shoff;
+		elf_parser.ehdr_shentsize	= ehdr32_shentsize;
+		elf_parser.ehdr_shstrndx	= ehdr32_shstrndx;
+		elf_parser.ehdr_shnum		= ehdr32_shnum;
+		elf_parser.shdr_addr		= shdr32_addr;
+		elf_parser.shdr_offset		= shdr32_offset;
+		elf_parser.shdr_link		= shdr32_link;
+		elf_parser.shdr_size		= shdr32_size;
+		elf_parser.shdr_name		= shdr32_name;
+		elf_parser.shdr_type		= shdr32_type;
+		elf_parser.shdr_entsize		= shdr32_entsize;
+		elf_parser.sym_type		= sym32_type;
+		elf_parser.sym_name		= sym32_name;
+		elf_parser.sym_value		= sym32_value;
+		elf_parser.sym_shndx		= sym32_shndx;
+		elf_parser.rela_offset		= rela32_offset;
+		elf_parser.rela_info		= rela32_info;
+		elf_parser.rela_addend		= rela32_addend;
+		elf_parser.rela_write_addend	= rela32_write_addend;
+
+		if (elf_parser.r2(&ehdr->e32.e_ehsize) != sizeof(Elf32_Ehdr) ||
+		    elf_parser.r2(&ehdr->e32.e_shentsize) != sizeof(Elf32_Shdr)) {
+			fprintf(stderr,
+				"unrecognized ET_EXEC/ET_DYN file: %s\n", fname);
+			return -1;
+		}
+
+		}
+		break;
+	case ELFCLASS64: {
+		elf_parser.ehdr_shoff		= ehdr64_shoff;
+		elf_parser.ehdr_shentsize		= ehdr64_shentsize;
+		elf_parser.ehdr_shstrndx		= ehdr64_shstrndx;
+		elf_parser.ehdr_shnum		= ehdr64_shnum;
+		elf_parser.shdr_addr		= shdr64_addr;
+		elf_parser.shdr_offset		= shdr64_offset;
+		elf_parser.shdr_link		= shdr64_link;
+		elf_parser.shdr_size		= shdr64_size;
+		elf_parser.shdr_name		= shdr64_name;
+		elf_parser.shdr_type		= shdr64_type;
+		elf_parser.shdr_entsize		= shdr64_entsize;
+		elf_parser.sym_type		= sym64_type;
+		elf_parser.sym_name		= sym64_name;
+		elf_parser.sym_value		= sym64_value;
+		elf_parser.sym_shndx		= sym64_shndx;
+		elf_parser.rela_offset		= rela64_offset;
+		elf_parser.rela_info		= rela64_info;
+		elf_parser.rela_addend		= rela64_addend;
+		elf_parser.rela_write_addend	= rela64_write_addend;
+
+		if (elf_parser.r2(&ehdr->e64.e_ehsize) != sizeof(Elf64_Ehdr) ||
+		    elf_parser.r2(&ehdr->e64.e_shentsize) != sizeof(Elf64_Shdr)) {
+			fprintf(stderr,
+				"unrecognized ET_EXEC/ET_DYN file: %s\n",
+				fname);
+			return -1;
+		}
+
+		}
+		break;
+	default:
+		fprintf(stderr, "unrecognized ELF class %d %s\n",
+			ehdr->e32.e_ident[EI_CLASS], fname);
+		return -1;
+	}
+	return 0;
+}
+
+int elf_map_machine(void *addr)
+{
+	Elf_Ehdr *ehdr = addr;
+
+	return elf_parser.r2(&ehdr->e32.e_machine);
+}
+
+int elf_map_long_size(void *addr)
+{
+	Elf_Ehdr *ehdr = addr;
+
+	return ehdr->e32.e_ident[EI_CLASS] == ELFCLASS32 ? 4 : 8;
+}
+
+void *elf_map(char const *fname, size_t *size, uint32_t types)
+{
+	void *addr;
+	int ret;
+
+	addr = map_file(fname, size);
+	if (!addr)
+		return NULL;
+
+	ret = elf_parse(fname, addr, types);
+	if (ret < 0) {
+		elf_unmap(addr, *size);
+		return NULL;
+	}
+
+	return addr;
+}
+
+void elf_unmap(void *addr, size_t size)
+{
+	munmap(addr, size);
+}