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Date:   Mon, 2 Apr 2018 07:44:37 +0100
From:   Al Viro <viro@ZenIV.linux.org.uk>
To:     Eric Biggers <ebiggers3@gmail.com>
Cc:     syzbot <syzbot+f3bd89a5ab3266b10540@syzkaller.appspotmail.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        syzkaller-bugs@googlegroups.com, linux-nfs@vger.kernel.org
Subject: Re: BUG: corrupted list in __dentry_kill
Message-ID: <20180402064437.GB30522@ZenIV.linux.org.uk>
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On Sun, Apr 01, 2018 at 02:48:54PM -0700, Eric Biggers wrote:
> [+Cc linux-nfs]
> > 
> > [   42.965515] net/sunrpc/rpc_pipe.c: __rpc_create_common failed to allocate inode for dentry blocklayout
> > [   42.967234] net/sunrpc/rpc_pipe.c: rpc_mkpipe_dentry() failed to create pipe nfs/blocklayout (errno = -12)

	AFAICS, there's nothing to zero nn->bl_device_pipe->dentry after
nfs4blocklayout_unregister_sb(), is there?  If nothing else, what's
going to happen after mount/umount/mount with failing
nfs4blocklayout_register_sb()?  AFAICS, we'll have stale pointer to
dentry sitting in nn->bl_device_pipe->dentry, and call rpc_unlink()
on it while cleaning up after the failing mount.

	I don't think that's all there is to it, but it does smell like
a bug.