linux-kernel - [PATCH] objtool: Fix ORC 'signal' propagation

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Message-Id: <97eef9db60cd86d376a9a40d49d77bb67a8f6526.1676579666.git.jpoimboe@kernel.org>
Date:   Thu, 16 Feb 2023 12:34:41 -0800
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        kernel test robot <oliver.sang@...el.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: [PATCH] objtool: Fix ORC 'signal' propagation

There have been some recently reported ORC unwinder warnings like:

  WARNING: can't access registers at entry_SYSCALL_64_after_hwframe+0x63/0xcd
  WARNING: stack going in the wrong direction? at __sys_setsockopt+0x2c6/0x5b0 net/socket.c:2271

And a KASAN warning:

  BUG: KASAN: stack-out-of-bounds in unwind_next_frame (arch/x86/include/asm/ptrace.h:136 arch/x86/kernel/unwind_orc.c:455)

It turns out the 'signal' bit isn't getting propagated from the unwind
hints to the ORC entries, making the unwinder confused at times.

Fixes: ffb1b4a41016 ("x86/unwind/orc: Add 'signal' field to ORC metadata")
Reported-by: kernel test robot <oliver.sang@...el.com>
Link: https://lore.kernel.org/oe-lkp/202302161616.85f13863-oliver.sang@intel.com
Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
Link: https://lkml.kernel.org/lkml/CACT4Y+YzZb2vscjBLiJ-p-ghbu77o851gbESfE=nZebXqfgE4g@mail.gmail.com/
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 tools/objtool/check.c               | 1 +
 tools/objtool/include/objtool/cfi.h | 1 +
 tools/objtool/orc_gen.c             | 1 +
 3 files changed, 3 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 7c40bd51c75a..8b242634bc51 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2266,6 +2266,7 @@ static int read_unwind_hints(struct objtool_file *file)
 
 		cfi.cfa.offset = bswap_if_needed(file->elf, hint->sp_offset);
 		cfi.type = hint->type;
+		cfi.signal = hint->signal;
 		cfi.end = hint->end;
 
 		insn->cfi = cfi_hash_find_or_add(&cfi);
diff --git a/tools/objtool/include/objtool/cfi.h b/tools/objtool/include/objtool/cfi.h
index f11d1ac1dadf..b1258e79a1b7 100644
--- a/tools/objtool/include/objtool/cfi.h
+++ b/tools/objtool/include/objtool/cfi.h
@@ -34,6 +34,7 @@ struct cfi_state {
 	unsigned char type;
 	bool bp_scratch;
 	bool drap;
+	bool signal;
 	bool end;
 };
 
diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
index 1f22b7ebae58..57a4527d5988 100644
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -27,6 +27,7 @@ static int init_orc_entry(struct orc_entry *orc, struct cfi_state *cfi,
 	}
 
 	orc->end = cfi->end;
+	orc->signal = cfi->signal;
 
 	if (cfi->cfa.base == CFI_UNDEFINED) {
 		orc->sp_reg = ORC_REG_UNDEFINED;
-- 
2.39.1