linux-kernel - [PATCH] virtio-blk: avoid kernel panic on VIRTIO_BLK_F

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Message-Id: <20221221140012.238494-1-lstoakes@gmail.com>
Date:   Wed, 21 Dec 2022 14:00:12 +0000
From:   Lorenzo Stoakes <lstoakes@...il.com>
To:     linux-block@...r.kernel.org,
        Dmitry Fomichev <dmitry.fomichev@....com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jens Axboe <axboe@...nel.dk>
Cc:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>,
        virtualization@...ts.linux-foundation.org,
        virtio-dev@...ts.oasis-open.org, linux-kernel@...r.kernel.org,
        Hannes Reinecke <hare@...e.de>,
        Sam Li <faithilikerun@...il.com>,
        Lorenzo Stoakes <lstoakes@...il.com>
Subject: [PATCH] virtio-blk: avoid kernel panic on VIRTIO_BLK_F_ZONED check

virtio zoned block device support is added by commit 0562d7bf1604
("virtio-blk: add support for zoned block devices") which adds
VIRTIO_BLK_F_ZONED to the features array in virtio_blk.c but makes it
conditional on CONFIG_BLK_DEV_ZONED.

In it virtblk_probe() calls virtio_has_feature(vdev, VIRTIO_BLK_F_ZONED)
unconditionally, which invokes virtio_check_driver_offered_feature().
This function checks whether virtio_blk.feature_table (assigned to
the static features array) contains the specified feature enum, and if not
_causes a kernel panic_ via BUG().

This therefore means that failing to enable CONFIG_BLK_DEV_ZONED while
using virtio is a guaranteed kernel panic. Fix the issue by making the
feature test also conditional on CONFIG_BLK_DEV_ZONED.

Signed-off-by: Lorenzo Stoakes <lstoakes@...il.com>
---
 drivers/block/virtio_blk.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index ff49052e26f7..34fdc141fb21 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -1580,11 +1580,13 @@ static int virtblk_probe(struct virtio_device *vdev)
 	virtblk_update_capacity(vblk, false);
 	virtio_device_ready(vdev);

+#ifdef CONFIG_BLK_DEV_ZONED
 	if (virtio_has_feature(vdev, VIRTIO_BLK_F_ZONED)) {
 		err = virtblk_probe_zoned_device(vdev, vblk, q);
 		if (err)
 			goto out_cleanup_disk;
 	}
+#endif /* CONFIG_BLK_DEV_ZONED */

 	dev_info(&vdev->dev, "blk config size: %zu\n",
 		sizeof(struct virtio_blk_config));
--
2.39.0