Re: [PATCH] virtio_ring: Fix mem leak with vring_new_virtqueue()

[Jason Wang]

On 2020/2/26 äå12:51, Suman Anna wrote:
> Hi Jason,
>
> On 2/24/20 11:39 PM, Jason Wang wrote:
> > On 2020/2/25 äå5:26, Suman Anna wrote:
> > > The functions vring_new_virtqueue() and __vring_new_virtqueue() are used
> > > with split rings, and any allocations within these functions are managed
> > > outside of the .we_own_ring flag. The commit cbeedb72b97a ("virtio_ring:
> > > allocate desc state for split ring separately") allocates the desc state
> > > within the __vring_new_virtqueue() but frees it only when the
> > > .we_own_ring
> > > flag is set. This leads to a memory leak when freeing such allocated
> > > virtqueues with the vring_del_virtqueue() function.
> > >
> > > Fix this by moving the desc_state free code outside the flag and only
> > > for split rings. Issue was discovered during testing with remoteproc
> > > and virtio_rpmsg.
> > >
> > > Fixes: cbeedb72b97a ("virtio_ring: allocate desc state for split ring
> > > separately")
> > > Signed-off-by: Suman Anna<s-anna@xxxxxx>
> > > ---
> > >  Â drivers/virtio/virtio_ring.c | 4 ++--
> > >  Â 1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> > > index 867c7ebd3f10..58b96baa8d48 100644
> > > --- a/drivers/virtio/virtio_ring.c
> > > +++ b/drivers/virtio/virtio_ring.c
> > > @@ -2203,10 +2203,10 @@ void vring_del_virtqueue(struct virtqueue *_vq)
> > >  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ vq->split.queue_size_in_bytes,
> > >  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ vq->split.vring.desc,
> > >  ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ vq->split.queue_dma_addr);
> > > -
> > > -ÂÂÂÂÂÂÂÂÂÂÂ kfree(vq->split.desc_state);
> > >  ÂÂÂÂÂÂÂÂÂ }
> > >  ÂÂÂÂÂ }
> > > +ÂÂÂ if (!vq->packed_ring)
> > > +ÂÂÂÂÂÂÂ kfree(vq->split.desc_state);
> > Nitpick, it looks to me it would be more clear if we just free
> > desc_state unconditionally here (and remove the kfree for packed above).
> OK, are you sure you want that to be folded into this patch? It looks to
> me a separate cleanup/consolidation patch, and packed desc_state does
> not suffer this memleak, and need not be backported into stable kernels.
>
> regards
> Suman


Though it's just a small tweak, I'm fine for leaving it for future.

So

Acked-by: Jason Wang <jasowang@xxxxxxxxxx>

Thanks