All of lore.kernel.org
 help / color / mirror / Atom feed
From: Andy Lutomirski <luto@amacapital.net>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Ingo Molnar <mingo@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"linux-tip-commits@vger.kernel.org" 
	<linux-tip-commits@vger.kernel.org>
Subject: Re: [tip:x86/urgent] x86/tls: Don't validate lm in set_thread_area() after all
Date: Thu, 18 Dec 2014 10:26:57 -0800	[thread overview]
Message-ID: <CALCETrU=+rBkG_xwaOA4vruiAeHFE_XLPrAgVCjnvpO5WrfgTw@mail.gmail.com> (raw)
In-Reply-To: <549307F0.7090009@zytor.com>

On Thu, Dec 18, 2014 at 8:59 AM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 12/18/2014 03:16 AM, tip-bot for Andy Lutomirski wrote:
>> Commit-ID:  3fb2f4237bb452eb4e98f6a5dbd5a445b4fed9d0
>> Gitweb:     http://git.kernel.org/tip/3fb2f4237bb452eb4e98f6a5dbd5a445b4fed9d0
>> Author:     Andy Lutomirski <luto@amacapital.net>
>> AuthorDate: Wed, 17 Dec 2014 14:48:30 -0800
>> Committer:  Ingo Molnar <mingo@kernel.org>
>> CommitDate: Thu, 18 Dec 2014 12:12:26 +0100
>>
>> x86/tls: Don't validate lm in set_thread_area() after all
>>
>> It turns out that there's a lurking ABI issue.  GCC, when
>> compiling this in a 32-bit program:
>>
>> struct user_desc desc = {
>>       .entry_number    = idx,
>>       .base_addr       = base,
>>       .limit           = 0xfffff,
>>       .seg_32bit       = 1,
>>       .contents        = 0, /* Data, grow-up */
>>       .read_exec_only  = 0,
>>       .limit_in_pages  = 1,
>>       .seg_not_present = 0,
>>       .useable         = 0,
>> };
>>
>> will leave .lm uninitialized.  This means that anything in the
>> kernel that reads user_desc.lm for 32-bit tasks is unreliable.
>>
>
> No, it won't.  However, if you initialize this dynamically field by
> field rather than as an initializer, then you are correct.
>

I tried the code above in function scope.

--Andy

>         -hpa
>



-- 
Andy Lutomirski
AMA Capital Management, LLC

  reply	other threads:[~2014-12-18 18:27 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-17 22:48 [PATCH resend] x86, tls: Don't validate lm in set_thread_area " Andy Lutomirski
2014-12-18 11:16 ` [tip:x86/urgent] x86/tls: Don't validate lm in set_thread_area() " tip-bot for Andy Lutomirski
2014-12-18 16:59   ` H. Peter Anvin
2014-12-18 18:26     ` Andy Lutomirski [this message]
2014-12-18 19:03     ` Linus Torvalds

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='CALCETrU=+rBkG_xwaOA4vruiAeHFE_XLPrAgVCjnvpO5WrfgTw@mail.gmail.com' \
    --to=luto@amacapital.net \
    --cc=hpa@zytor.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-tip-commits@vger.kernel.org \
    --cc=mingo@kernel.org \
    --cc=tglx@linutronix.de \
    --cc=torvalds@linux-foundation.org \
    --subject='Re: [tip:x86/urgent] x86/tls: Don'\''t validate lm in set_thread_area() after all' \
    /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

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.