While cloning a reloc, klp diff calls find_export() to determine whether
the referenced symbol is exported. That decides whether the reference
needs a klp reloc, which object the klp symbol belongs to, and whether
the symbol's data needs to be copied into the patch module.
But find_export() matches purely on symbol name, so a static function or
variable which happens to share its name with an export is mistaken for
a reference to that export:
- klp_reloc_needed() creates a klp reloc pointing at the exporting
module's symbol rather than the local one. For a vmlinux export it
skips the klp reloc altogether, leaving a normal reloc which the
module loader resolves to the vmlinux symbol.
- clone_reloc() treats the symbol as external and clones it without
its data, leaving a dangling reference.
- validate_special_section_klp_reloc() attributes a static branch or
call key to the wrong module, and for a vmlinux export skips the
unsupported-key check entirely.
Exports are always global, so ignore local symbols in find_export().
Fixes: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing
object files")
Signed-off-by: Josh Poimboeuf <[email protected]>
---
tools/objtool/klp-diff.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c
index 91a9562c45a6e..aebe68a401571 100644
--- a/tools/objtool/klp-diff.c
+++ b/tools/objtool/klp-diff.c
@@ -1101,6 +1101,9 @@ static struct export *find_export(struct symbol *sym)
{
struct export *export;
+ if (is_local_sym(sym))
+ return NULL;
+
hash_for_each_possible(exports, export, hash, str_hash(sym->name)) {
if (!strcmp(export->sym, sym->name))
return export;
--
2.54.0
