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

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Message-ID: <20190325234439.jimxj6q4bs5ndrwf@ast-mbp>
Date:   Mon, 25 Mar 2019 16:44:40 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        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 11:37:32PM +0000, Al Viro wrote:
> 
> For debugfs it's clearly "use default ->evict_inode(), have explicit
> ->destroy_inode() using free_inode_nonrcu()" - there we have nothing
> else done in ->evict_inode() and kfree is obviously safe in softirq.
> I'll post that (or push to vfs.git#fixes), along with minimal fixes
> for other 3.  If bpf_any_put() is softirq-safe, we'll have the full
> set for -stable and the rest could be done on top of that.

Yes. bpf_any_put() is safe to be called from softirq.