linux-kernel - Re: [PATCH v3 12/24] erofs: introduce tagged pointer

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: <20190722104048.463397a0@gandalf.local.home>
Date:   Mon, 22 Jul 2019 10:40:48 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Amir Goldstein <amir73il@...il.com>
Cc:     Gao Xiang <gaoxiang25@...wei.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        "Theodore Ts'o" <tytso@....edu>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        devel@...verdev.osuosl.org, LKML <linux-kernel@...r.kernel.org>,
        linux-erofs@...ts.ozlabs.org, Chao Yu <yuchao0@...wei.com>,
        Miao Xie <miaoxie@...wei.com>,
        Li Guifu <bluce.liguifu@...wei.com>,
        Fang Wei <fangwei1@...wei.com>, Ingo Molnar <mingo@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3 12/24] erofs: introduce tagged pointer

On Mon, 22 Jul 2019 09:16:22 +0300
Amir Goldstein <amir73il@...il.com> wrote:

> CC kernel/trace maintainers for RB_PAGE_HEAD/RB_PAGE_UPDATE
> and kernel/locking maintainers for RT_MUTEX_HAS_WAITERS

Interesting.

> 
> > (Is there some use scenerios in overlayfs and fanotify?...)  
> 
> We had one in overlayfs once. It is gone now.
> 
> >
> > and I'm not sure Al could accept __fdget conversion (I just wanted to give a example then...)
> >
> > Therefore, I tend to keep silence and just promote EROFS... some better ideas?...
> >  
> 
> Writing example conversion patches to demonstrate cleaner code
> and perhaps reduce LOC seems the best way.

Yes, I would be more interested in seeing patches that clean up the
code than just talking about it.

> 
> Also pointing out that fixing potential bugs in one implementation is preferred
> to having to patch all copied implementations.
> 
> I wonder if tagptr_unfold_tags() doesn't need READ_ONCE() as per:
> 1be5d4fa0af3 locking/rtmutex: Use READ_ONCE() in rt_mutex_owner()
> 
> rb_list_head() doesn't have READ_ONCE()

Hmm, even if the compiler decided to reread the data, it would still
need to clear the extra bits wouldn't it? Or am I missing something?

-- Steve

> Nor does hlist_bl_first() and BPF_MAP_PTR().
> 
> Are those all safe due to safe call sites? or potentially broken?