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From: Kees Cook <keescook@chromium.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Randy Dunlap <rdunlap@infradead.org>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Linux Next Mailing List <linux-next@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: linux-next: Tree for Mar 18 (objtool)
Date: Wed, 25 Mar 2020 22:57:02 -0700	[thread overview]
Message-ID: <202003252251.771EF5EC5F@keescook> (raw)
In-Reply-To: <20200324222406.zg6hylzqux353jhq@treble>

On Tue, Mar 24, 2020 at 05:24:06PM -0500, Josh Poimboeuf wrote:
> On Tue, Mar 24, 2020 at 11:18:07AM -0700, Kees Cook wrote:
> > As far as I could tell, this needs patches to the UBSAN support in gcc
> > and clang. I have opened bugs for each:
> > 
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94307
> > https://bugs.llvm.org/show_bug.cgi?id=45295
> 
> So it sounds like this would replace the second UD2 with a "call
> some_ubsan_function()"?
> 
> That might be slightly better, though it would still need an objtool
> change to ignore unreachable warnings for such calls.

Well, there are basically two modes (actually three as I've just
discovered on the clang bug): warn and fail. I hadn't found a way to get
"small" warns, so I wired up the fail path which injects an
"unreachable" as part of its logic.

> In the meantime I can still change objtool to ignore unreachable UD2s if
> there aren't any better ideas.

It'll still need the objtool change for CONFIG_UBSAN_TRAP, though based on
the clang bug discussion, I'll probably _also_ be adding CONFIG_UBSAN_WARN
which won't have an unreachable (and won't bloat the kernel). Testing
still under way... it is possible that CONFIG_UBSAN_TRAP will go away
in the future, though. If that happens, should I also remove the change
at that time?

-- 
Kees Cook

  reply	other threads:[~2020-03-26  5:57 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-18 11:09 linux-next: Tree for Mar 18 Stephen Rothwell
2020-03-18 16:14 ` linux-next: Tree for Mar 18 (drivers/base/power/sysfs.c) Randy Dunlap
2020-03-19  3:20   ` Stephen Rothwell
2020-03-19 14:47     ` [PATCH net-next] sysfs: fix static inline declaration of sysfs_groups_change_owner() Christian Brauner
2020-03-19 16:19       ` Randy Dunlap
2020-03-20  4:17       ` David Miller
2020-03-18 16:48 ` linux-next: Tree for Mar 18 (objtool) Randy Dunlap
2020-03-18 16:55   ` Josh Poimboeuf
2020-03-18 18:23   ` Josh Poimboeuf
2020-03-18 20:05     ` Peter Zijlstra
2020-03-19 11:12       ` Peter Zijlstra
2020-03-19 17:31       ` Josh Poimboeuf
2020-03-19 17:33         ` Josh Poimboeuf
2020-03-19 17:40           ` Josh Poimboeuf
2020-03-19 17:45             ` Josh Poimboeuf
2020-03-20  8:26               ` Peter Zijlstra
2020-03-20 18:35                 ` Kees Cook
2020-03-24 16:44                   ` Josh Poimboeuf
2020-03-24 18:18                     ` Kees Cook
2020-03-24 22:24                       ` Josh Poimboeuf
2020-03-26  5:57                         ` Kees Cook [this message]
2020-03-26 16:31                           ` Josh Poimboeuf
2020-03-26 18:36                             ` Kees Cook
2020-03-27  3:55                               ` Josh Poimboeuf

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