From: "H. Peter Anvin" <hpa@zytor.com>
To: Andy Lutomirski <luto@amacapital.net>,
Denys Vlasenko <dvlasenk@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.org>, Borislav Petkov <bp@alien8.de>,
Oleg Nesterov <oleg@redhat.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Alexei Starovoitov <ast@plumgrid.com>,
Will Drewry <wad@chromium.org>, Kees Cook <keescook@chromium.org>,
X86 ML <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/4] x86: entry.S: tidy up several suboptimal insns
Date: Tue, 24 Feb 2015 14:52:37 -0800 [thread overview]
Message-ID: <54ED00B5.3020203@zytor.com> (raw)
In-Reply-To: <CALCETrVretXX1Wgx9TNQH67XH=M6fGA+L+7agyp0Fm8503Ey9w@mail.gmail.com>
On 02/24/2015 02:25 PM, Andy Lutomirski wrote:
> On Tue, Feb 24, 2015 at 10:51 AM, Denys Vlasenko <dvlasenk@redhat.com> wrote:
>> In all three 32-bit entry points, %eax is zero-extended to %rax.
>> It is safe to do 32-bit compare when checking that syscall#
>> is not too large.
>
> Applied. Thanks!
>
NAK NAK NAK NAK NAK!!!!
We have already had this turn into a security issue not just once but
TWICE, because someone decided to "optimize" the path by taking out the
zero extend.
The use of a 64-bit compare here is an intentional "belts and
suspenders" safety issue.
-hpa
next prev parent reply other threads:[~2015-02-24 22:53 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-24 18:51 [PATCH 1/4] x86: entry.S: tidy up several suboptimal insns Denys Vlasenko
2015-02-24 18:51 ` [PATCH 2/4] x86: get rid of KERNEL_STACK_OFFSET Denys Vlasenko
2015-02-24 19:30 ` Steven Rostedt
2015-02-24 20:02 ` Denys Vlasenko
2015-02-24 22:37 ` Andy Lutomirski
2015-02-25 9:45 ` Ingo Molnar
2015-02-25 16:14 ` Andy Lutomirski
2015-02-26 11:42 ` Ingo Molnar
2015-02-26 15:21 ` Andy Lutomirski
2015-02-26 15:29 ` Andy Lutomirski
2015-02-25 8:53 ` Ingo Molnar
2015-02-25 12:48 ` Denys Vlasenko
2015-02-25 13:25 ` Denys Vlasenko
2015-02-25 13:53 ` Ingo Molnar
2015-02-24 18:51 ` [PATCH 3/4] x86: save r11 into pt_regs->eflags on SYSCALL64 fastpath Denys Vlasenko
2015-02-24 22:44 ` Andy Lutomirski
2015-02-24 18:51 ` [PATCH 4/4] x86: save user %rsp in pt_regs->sp Denys Vlasenko
2015-02-24 22:55 ` Andy Lutomirski
2015-02-24 19:58 ` [PATCH 1/4] x86: entry.S: tidy up several suboptimal insns Borislav Petkov
2015-02-24 20:13 ` Denys Vlasenko
2015-02-24 20:36 ` Borislav Petkov
2015-02-24 22:51 ` H. Peter Anvin
2015-02-24 22:25 ` Andy Lutomirski
2015-02-24 22:52 ` H. Peter Anvin [this message]
2015-02-24 22:56 ` Andy Lutomirski
2015-02-24 23:01 ` H. Peter Anvin
2015-02-24 23:03 ` Andy Lutomirski
2015-02-24 23:26 ` Denys Vlasenko
2015-02-25 9:20 ` Ingo Molnar
2015-02-25 9:27 ` H. Peter Anvin
2015-02-25 9:39 ` Ingo Molnar
2015-02-25 14:43 ` Steven Rostedt
2015-02-25 15:40 ` Denys Vlasenko
2015-02-25 16:01 ` Steven Rostedt
2015-02-25 16:06 ` Borislav Petkov
2015-02-26 11:47 ` Ingo Molnar
2015-02-26 12:47 ` Steven Rostedt
2015-02-26 12:50 ` Steven Rostedt
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=54ED00B5.3020203@zytor.com \
--to=hpa@zytor.com \
--cc=ast@plumgrid.com \
--cc=bp@alien8.de \
--cc=dvlasenk@redhat.com \
--cc=fweisbec@gmail.com \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=rostedt@goodmis.org \
--cc=torvalds@linux-foundation.org \
--cc=wad@chromium.org \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.