Re: [PATCH 1/2] fuse: virtiofs: Fix nullptr dereference

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Mon, Apr 27, 2020 at 01:58:14PM -0400, Vivek Goyal wrote:
> On Fri, Apr 24, 2020 at 03:25:39PM +0900, Chirantan Ekbote wrote:
> > virtiofs device implementations are allowed to provide more than one
> > request queue.  In this case `fsvq->fud` would not be initialized,
> > leading to a nullptr dereference later during driver initialization.
> > 
> > Make sure that `fsvq->fud` is initialized for all request queues even if
> > the driver doesn't use them.
> > 
> > Signed-off-by: Chirantan Ekbote <chirantan@chromium.org>
> > ---
> >  fs/fuse/virtio_fs.c | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
> > index bade747689033..d3c38222a7e4e 100644
> > --- a/fs/fuse/virtio_fs.c
> > +++ b/fs/fuse/virtio_fs.c
> > @@ -1066,10 +1066,13 @@ static int virtio_fs_fill_super(struct super_block *sb)
> >  	}
> >  
> >  	err = -ENOMEM;
> > -	/* Allocate fuse_dev for hiprio and notification queues */
> > -	for (i = 0; i < VQ_REQUEST; i++) {
> > +	/* Allocate fuse_dev for all queues except the first request queue. */
> > +	for (i = 0; i < fs->nvqs; i++) {
> >  		struct virtio_fs_vq *fsvq = &fs->vqs[i];
> >  
> > +		if (i == VQ_REQUEST)
> > +			continue;
> > +
> 
> These special conditions of initializing fuse device for one queue
> fusing fill_super_common() and rest of the queues outside of it, are
> bothering me. I am proposing a separate patch where all fuse device
> initialization/cleanup is done by the caller. It makes code look
> cleaner and easier to understand.

Nice!

Stefan

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