linux-kernel - Re: [RFC][PATCH v3] ftrace/x86_64: Emulate call function while updating in breakpoint handler

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]

Message-ID: <20190501191716.GV7905@worktop.programming.kicks-ass.net>
Date:   Wed, 1 May 2019 21:17:16 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Andy Lutomirski <luto@...nel.org>,
        Nicolai Stange <nstange@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Shuah Khan <shuah@...nel.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Juergen Gross <jgross@...e.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nayna Jain <nayna@...ux.ibm.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Joerg Roedel <jroedel@...e.de>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        live-patching@...r.kernel.org,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>
Subject: Re: [RFC][PATCH v3] ftrace/x86_64: Emulate call function while
 updating in breakpoint handler

On Wed, May 01, 2019 at 11:59:05AM -0700, Linus Torvalds wrote:
> On Wed, May 1, 2019 at 11:52 AM Steven Rostedt <rostedt@...dmis.org> wrote:
> >
> > I got Peter's patch working. Here it is. What do you think?
> 
> I can tell from just looking at it for five seconds that at least the
> 32-bit case is buggy.
> 
> You can't look at CS(%rsp) without first also checking that you're not
> coming from vm86 mode.

Something like so then?

Index: linux-2.6/arch/x86/entry/entry_32.S
===================================================================
--- linux-2.6.orig/arch/x86/entry/entry_32.S
+++ linux-2.6/arch/x86/entry/entry_32.S
@@ -1479,6 +1479,10 @@ ENTRY(int3)
 	ASM_CLAC
 	pushl	$-1				# mark this as an int

+#ifdef CONFIG_VM86
+	testl	$X86_EFLAGS_VM, PT_EFLAGS(%esp)
+	jnz	.Lfrom_usermode_no_gap
+#endif
 	testl	$SEGMENT_RPL_MASK, PT_CS(%esp)
 	jnz	.Lfrom_usermode_no_gap
 	.rept 6