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Tsirkin" To: Jason Wang Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, xuanzhuo@linux.alibaba.com Subject: Re: [PATCH net V5] virtio-net: fix the race between refill work and close Message-ID: <20220704045034-mutt-send-email-mst@kernel.org> References: <20220704074859.16912-1-jasowang@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220704074859.16912-1-jasowang@redhat.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Jul 04, 2022 at 03:48:59PM +0800, Jason Wang wrote: > We try using cancel_delayed_work_sync() to prevent the work from > enabling NAPI. This is insufficient since we don't disable the source > of the refill work scheduling. This means an NAPI poll callback after > cancel_delayed_work_sync() can schedule the refill work then can > re-enable the NAPI that leads to use-after-free [1]. > > Since the work can enable NAPI, we can't simply disable NAPI before > calling cancel_delayed_work_sync(). So fix this by introducing a > dedicated boolean to control whether or not the work could be > scheduled from NAPI. > > [1] > ================================================================== > BUG: KASAN: use-after-free in refill_work+0x43/0xd4 > Read of size 2 at addr ffff88810562c92e by task kworker/2:1/42 > > CPU: 2 PID: 42 Comm: kworker/2:1 Not tainted 5.19.0-rc1+ #480 > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 > Workqueue: events refill_work > Call Trace: > > dump_stack_lvl+0x34/0x44 > print_report.cold+0xbb/0x6ac > ? _printk+0xad/0xde > ? refill_work+0x43/0xd4 > kasan_report+0xa8/0x130 > ? refill_work+0x43/0xd4 > refill_work+0x43/0xd4 > process_one_work+0x43d/0x780 > worker_thread+0x2a0/0x6f0 > ? process_one_work+0x780/0x780 > kthread+0x167/0x1a0 > ? kthread_exit+0x50/0x50 > ret_from_fork+0x22/0x30 > > ... > > Fixes: b2baed69e605c ("virtio_net: set/cancel work on ndo_open/ndo_stop") > Signed-off-by: Jason Wang Acked-by: Michael S. Tsirkin > --- > Changes since V4: > - Tweak the variable name (using delayed_refill) > Changes since V3: > - rebase to -net > Changes since V2: > - use spin_unlock()/lock_bh() in open/stop to synchronize with bh > Changes since V1: > - Tweak the changelog > --- > drivers/net/virtio_net.c | 35 +++++++++++++++++++++++++++++++++-- > 1 file changed, 33 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 356cf8dd4164..b9ac4431becb 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -245,6 +245,12 @@ struct virtnet_info { > /* Work struct for refilling if we run low on memory. */ let's update this comment to "for delayed refilling" for consistency > struct delayed_work refill; > > + /* Is delayed refill enabled? */ > + bool delayed_refill_enabled; I would keep the name refill_enabled, refill refers to the field "refill" above. > + > + /* The lock to synchronize the access to delayed_refill_enabled */ add: ... and to refill > + spinlock_t refill_lock; > + > /* Work struct for config space updates */ > struct work_struct config_work; > > @@ -348,6 +354,20 @@ static struct page *get_a_page(struct receive_queue *rq, gfp_t gfp_mask) > return p; > } > > +static void enable_delayed_refill(struct virtnet_info *vi) > +{ > + spin_lock_bh(&vi->refill_lock); > + vi->delayed_refill_enabled = true; > + spin_unlock_bh(&vi->refill_lock); > +} > + > +static void disable_delayed_refill(struct virtnet_info *vi) > +{ > + spin_lock_bh(&vi->refill_lock); > + vi->delayed_refill_enabled = false; > + spin_unlock_bh(&vi->refill_lock); > +} > + > static void virtqueue_napi_schedule(struct napi_struct *napi, > struct virtqueue *vq) > { > @@ -1527,8 +1547,12 @@ static int virtnet_receive(struct receive_queue *rq, int budget, > } > > if (rq->vq->num_free > min((unsigned int)budget, virtqueue_get_vring_size(rq->vq)) / 2) { > - if (!try_fill_recv(vi, rq, GFP_ATOMIC)) > - schedule_delayed_work(&vi->refill, 0); > + if (!try_fill_recv(vi, rq, GFP_ATOMIC)) { > + spin_lock(&vi->refill_lock); > + if (vi->delayed_refill_enabled) > + schedule_delayed_work(&vi->refill, 0); > + spin_unlock(&vi->refill_lock); > + } > } > > u64_stats_update_begin(&rq->stats.syncp); > @@ -1651,6 +1675,8 @@ static int virtnet_open(struct net_device *dev) > struct virtnet_info *vi = netdev_priv(dev); > int i, err; > > + enable_delayed_refill(vi); > + > for (i = 0; i < vi->max_queue_pairs; i++) { > if (i < vi->curr_queue_pairs) > /* Make sure we have some buffers: if oom use wq. */ > @@ -2033,6 +2059,8 @@ static int virtnet_close(struct net_device *dev) > struct virtnet_info *vi = netdev_priv(dev); > int i; > > + /* Make sure NAPI doesn't schedule refill work */ > + disable_delayed_refill(vi); > /* Make sure refill_work doesn't re-enable napi! */ > cancel_delayed_work_sync(&vi->refill); > > @@ -2792,6 +2820,8 @@ static int virtnet_restore_up(struct virtio_device *vdev) > > virtio_device_ready(vdev); > > + enable_delayed_refill(vi); > + > if (netif_running(vi->dev)) { > err = virtnet_open(vi->dev); > if (err) > @@ -3535,6 +3565,7 @@ static int virtnet_probe(struct virtio_device *vdev) > vdev->priv = vi; > > INIT_WORK(&vi->config_work, virtnet_config_changed_work); > + spin_lock_init(&vi->refill_lock); > > /* If we can receive ANY GSO packets, we must allocate large ones. */ > if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) || > -- > 2.25.1