All of lore.kernel.org
 help / color / mirror / Atom feed
From: Randy Dunlap <rdunlap@infradead.org>
To: Kees Cook <keescook@chromium.org>, Peter Zijlstra <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-kernel@vger.kernel.org, aryabinin@virtuozzo.com,
	dvyukov@google.com
Subject: Re: [PATCH] mm/uaccess: Use 'unsigned long' to placate UBSAN warnings, again
Date: Wed, 6 Jan 2021 16:06:57 -0800	[thread overview]
Message-ID: <d5b192b2-b216-57d1-4505-06233ae2b882@infradead.org> (raw)
In-Reply-To: <202101061536.C4A93132@keescook>

On 1/6/21 3:37 PM, Kees Cook wrote:
> On Mon, Jan 04, 2021 at 04:13:17PM +0100, Peter Zijlstra wrote:
>> On Tue, Dec 22, 2020 at 11:04:54PM -0600, Josh Poimboeuf wrote:
>>> GCC 7 has a known bug where UBSAN ignores '-fwrapv' and generates false
>>> signed-overflow-UB warnings.  The type mismatch between 'i' and
>>> 'nr_segs' in copy_compat_iovec_from_user() is causing such a warning,
>>> which also happens to violate uaccess rules:
>>>
>>>   lib/iov_iter.o: warning: objtool: iovec_from_user()+0x22d: call to __ubsan_handle_add_overflow() with UACCESS enabled
>>>
>>> Fix it by making the variable types match.
>>>
>>> This is similar to a previous commit:
>>>
>>>   29da93fea3ea ("mm/uaccess: Use 'unsigned long' to placate UBSAN warnings on older GCC versions")
>>
>> Maybe it's time we make UBSAN builds depend on GCC-8+ ?
> 
> I would be totally fine with that. The only thing I can think of that
> might care is syzbot. Dmitry, does syzbot use anything older than gcc 8?

I use UBSAN successfully with GCC 7.5.0.
However, I can revert whatever future patch someone adds for this...

-- 
~Randy


  reply	other threads:[~2021-01-07  0:07 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-23  5:04 [PATCH] mm/uaccess: Use 'unsigned long' to placate UBSAN warnings, again Josh Poimboeuf
2020-12-23  7:18 ` Randy Dunlap
2021-01-07 10:06   ` David Laight
2021-01-04 15:13 ` Peter Zijlstra
2021-01-06 23:37   ` Kees Cook
2021-01-07  0:06     ` Randy Dunlap [this message]
2021-01-07 21:07       ` Kees Cook
2021-01-13 23:27         ` Josh Poimboeuf
2021-01-07 10:51     ` Dmitry Vyukov
2021-01-14 10:59   ` [PATCH] ubsan: Require GCC-8+ or Clang to use UBSAN Peter Zijlstra
2021-01-14 11:09     ` Andrey Ryabinin
2021-01-18 17:53       ` Josh Poimboeuf
2021-02-09 18:24         ` Josh Poimboeuf
2021-02-09 23:17           ` Andrey Rybainin
2021-02-10  0:21             ` Kees Cook

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=d5b192b2-b216-57d1-4505-06233ae2b882@infradead.org \
    --to=rdunlap@infradead.org \
    --cc=aryabinin@virtuozzo.com \
    --cc=dvyukov@google.com \
    --cc=jpoimboe@redhat.com \
    --cc=keescook@chromium.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=peterz@infradead.org \
    --cc=viro@zeniv.linux.org.uk \
    /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.