objtool: Fix SEGFAULT

find_insn() will return NULL in case of failure. Check insn in order
to avoid a kernel Oops for NULL pointer dereference.

Tested-by: Naveen N. Rao <[email protected]>
Reviewed-by: Naveen N. Rao <[email protected]>
Acked-by: Josh Poimboeuf <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Christophe Leroy <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: chleroy

tools/objtool/check.c

@@ -207,7 +207,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
 		return false;
 
 	insn = find_insn(file, func->sec, func->offset);
-	if (!insn->func)
+	if (!insn || !insn->func)
 		return false;
 
 	func_for_each_insn(file, func, insn) {