linux-kernel - Re: KCSAN: data-race in __alloc_file / __alloc

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Message-ID: <CAHk-=whPFjpOEfU5N4qz_gGC8_=NLh1VkBLm09K1S1Gcma5pzA@mail.gmail.com>
Date:   Tue, 12 Nov 2019 09:36:41 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Kirill Smelkov <kirr@...edi.com>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Alan Stern <stern@...land.harvard.edu>,
        Marco Elver <elver@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        syzbot <syzbot+3ef049d50587836c0606@...kaller.appspotmail.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Andrea Parri <parri.andrea@...il.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        LKMM Maintainers -- Akira Yokosawa <akiyks@...il.com>
Subject: Re: KCSAN: data-race in __alloc_file / __alloc_file

On Tue, Nov 12, 2019 at 9:23 AM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Hmm. I thought we already then applied all the patches that marked
> things that didn't use f_pos as FMODE_STREAM. Including pipes and
> sockets etc.
>
> But if we didn't - and no, I didn't double-check now either - then
> obviously that part of the patch can't be applied now.

Ok, looking at it now.

Yeah, commit c5bf68fe0c86 ("*: convert stream-like files from
nonseekable_open -> stream_open") did the scripted thing, but it only
did it for nonseekable_open, not for the more complicated cases.

So yup, you're right - we'd need to at least do the pipe/socket case too.

What happens if the actual conversion part (nonseekable_open ->
stream_open) is removed from the cocci script, and it's used to only
find "read/write doesn't use f_pos" cases?

Or maybe trigger on '.llseek = no_llseek'?

                 Linus