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

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Message-ID: <CAHk-=wjD-A_VsYC_OKcn30_ZsrLEE1CN7mnwZ803cvaFTdTTfA@mail.gmail.com>
Date:   Mon, 25 Mar 2019 15:13:40 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        syzbot <syzbot+7a8ba368b47fdefca61e@...kaller.appspotmail.com>,
        Alexei Starovoitov <ast@...nel.org>,
        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 3:04 PM Daniel Borkmann <daniel@...earbox.net> wrote:
>
> I'm fine either way, I think the rcu_destroy_inode would indeed simplify
> it nicely. In any case fwiw, here's what I'd have ready for standby on bpf
> side and tested as well. Decided to get rid of bpf_evict_inode() entirely
> since the only callback we'd really need is on final inode destruction:

Yes, this looks correct to me.

I think this is worth doing regardless. Even if we then make the vfs
layer add that rcu_destroy_inode(), that will fit very well with this
patch, and getting rid of the special bpf_evict_inode() logic and just
letting the normal vfs inode cleanup happen looks like the right
thing.

So ack from me on your

> Subject: [PATCH bpf] bpf: fix use after free in bpf_evict_inode

patch regardless of what else we might end up doing in this area to
clean things up.

                 Linus