[PATCH 1/3] objtool: Fix seg fault in ignore_unreachable_insn()

[Josh Poimboeuf]

Check prev_insn before dereferencing it.

Fixes: bd841d6154f5 ("objtool: Fix CONFIG_UBSAN_TRAP unreachable warnings")
Reported-by: Arnd Bergmann <arnd@xxxxxxxx>
Closes: https://lore.kernel.org/d86b4cc6-0b97-4095-8793-a7384410b8ab@xxxxxxxxxxxxxxxx
Reported-by: Ingo Molnar <mingo@xxxxxxxxxx>
Closes: https://lore.kernel.org/Z-V_rruKY0-36pqA@xxxxxxxxx
Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
 tools/objtool/check.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 3bf29923d5c0..29de1709ea00 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4037,7 +4037,7 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
 	 * It may also insert a UD2 after calling a __noreturn function.
 	 */
 	prev_insn = prev_insn_same_sec(file, insn);
-	if (prev_insn->dead_end &&
+	if (prev_insn && prev_insn->dead_end &&
 	    (insn->type == INSN_BUG ||
 	     (insn->type == INSN_JUMP_UNCONDITIONAL &&
 	      insn->jump_dest && insn->jump_dest->type == INSN_BUG)))
-- 
2.48.1