linux-kernel - [PATCH v8 01/12] objtool: Detect jumps to retpoline thunks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 11 Jan 2018 21:46:23 +0000
From:   David Woodhouse <dwmw@...zon.co.uk>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Paul Turner <pjt@...gle.com>, LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>, tglx@...utronix.de,
        Kees Cook <keescook@...gle.com>,
        Rik van Riel <riel@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        Jiri Kosina <jikos@...nel.org>, gnomes@...rguk.ukuu.org.uk,
        x86@...nel.org, thomas.lendacky@....com,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: [PATCH v8 01/12] objtool: Detect jumps to retpoline thunks

From: Josh Poimboeuf <jpoimboe@...hat.com>

A direct jump to a retpoline thunk is really an indirect jump in
disguise.  Change the objtool instruction type accordingly.

Objtool needs to know where indirect branches are so it can detect
switch statement jump tables.

This fixes a bunch of warnings with CONFIG_RETPOLINE like:

  arch/x86/events/intel/uncore_nhmex.o: warning: objtool: nhmex_rbox_msr_enable_event()+0x44: sibling call from callable instruction with modified stack frame
  kernel/signal.o: warning: objtool: copy_siginfo_to_user()+0x91: sibling call from callable instruction with modified stack frame
  ...

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
---
 tools/objtool/check.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 9b341584..de053fb 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -456,6 +456,13 @@ static int add_jump_destinations(struct objtool_file *file)
 		} else if (rela->sym->sec->idx) {
 			dest_sec = rela->sym->sec;
 			dest_off = rela->sym->sym.st_value + rela->addend + 4;
+		} else if (strstr(rela->sym->name, "_indirect_thunk_")) {
+			/*
+			 * Retpoline jumps are really dynamic jumps in
+			 * disguise, so convert them accordingly.
+			 */
+			insn->type = INSN_JUMP_DYNAMIC;
+			continue;
 		} else {
 			/* sibling call */
 			insn->jump_dest = 0;
-- 
2.7.4