linux-kernel - Re: [uml-devel] SYSCALL, ptrace and syscall restart breakages (Re: [RFC] weird crap with vdso on uml/i386)

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: <20110823000705.GX2203@ZenIV.linux.org.uk>
Date:	Tue, 23 Aug 2011 01:07:05 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Andrew Lutomirski <luto@....edu>,
	Borislav Petkov <bp@...64.org>, Ingo Molnar <mingo@...nel.org>,
	"user-mode-linux-devel@...ts.sourceforge.net" 
	<user-mode-linux-devel@...ts.sourceforge.net>,
	Richard Weinberger <richard@....at>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...hat.com" <mingo@...hat.com>
Subject: Re: [uml-devel] SYSCALL, ptrace and syscall restart breakages (Re:
 [RFC] weird crap with vdso on uml/i386)

On Tue, Aug 23, 2011 at 01:03:14AM +0100, Al Viro wrote:
> On Mon, Aug 22, 2011 at 04:27:51PM -0700, Linus Torvalds wrote:
> 
> > So I think the "let's fix the vdso case for sysenter" + "let's remove
> > the 32-bit syscall vdso" is the right solution. If somebody has
> > hardcoded syscall instructions, or generates them dynamically with
> > some JIT, that's their problem. We'll continue to support it as well
> > as we ever have (read: "almost nobody will ever notice").
> 
> Umm...  Maybe, but I really wonder if it would be better to do this:
> 	* check if %ecx is the right one for vdso32 entry.  If it isn't,
> act as we act now (and possibly warn).  If it is, increment it by 4.
> 	* slap 0x90, 0x90, 0xcd, 0x80 right after that syscall insn -
> i.e. nop/nop/int 0x80.  Followed by what we currently do there.
> 
> 	Those who do syscall insn in 32bit mode outside of vdso will get
> what they currently get.  __kernel_vsyscall() will keep working and do
> that without restart problems.  And the price is comparison + branch not
> taken + addition for that path...

s/whine/set your "don't restart that one" flag/, even...
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/