linux-kernel - Re: KASAN: use-after-free Read in path

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Message-ID: <CAHk-=whJ4M5FegOLvnjUtJ0+pHv4L8UNFt+9jJDhox3Ada8kwA@mail.gmail.com>
Date:   Mon, 25 Mar 2019 12:18:02 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     syzbot <syzbot+7a8ba368b47fdefca61e@...kaller.appspotmail.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: KASAN: use-after-free Read in path_lookupat

On Mon, Mar 25, 2019 at 11:36 AM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> >
> > You mean, split ->destroy_inode() into immediate and RCU-delayed parts?
> > There are filesystems where both parts are non-empty - we can't just
> > switch all ->destroy_inode() work to call_rcu().
>
> Right. Not just move the existing destroy_inode() - because as you
> say, people may not be able to to do that in RCU contect, but split it
> up, and add a "final_free_inode()" callback or something for the RCU
> phase.

Something like the attached.

COMPLETELY UNTESTED. And no filesystems converted to actually use the
new rcu_destroy_inode() thing.

Hmm?

                Linus

View attachment "patch.diff" of type "text/x-patch" (3424 bytes)