objtool: Make BP scratch register warning more robust

If func is NULL, a seg fault can result.

This is a theoretical issue which was found by Coverity, ID: 1492002
("Dereference after null check").

Fixes: c705cecc8431 ("objtool: Track original function across branches")
Reported-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/afc628693a37acd287e843bcc5c0430263d93c74.1585761021.git.jpoimboe@redhat.com

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index cb2d299..4b170fd 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2005,8 +2005,8 @@ static int validate_return(struct symbol *func, struct instruction *insn, struct
        }
 
        if (state->bp_scratch) {
-               WARN("%s uses BP as a scratch register",
-                    func->name);
+               WARN_FUNC("BP used as a scratch register",
+                         insn->sec, insn->offset);
                return 1;
        }