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virtio: acknowledge all features before access
commit4fa59ede95
upstream. The feature negotiation was designed in a way that makes it possible for devices to know which config fields will be accessed by drivers. This is broken since commit404123c2db
("virtio: allow drivers to validate features") with fallout in at least block and net. We have a partial work-around in commit2f9a174f91
("virtio: write back F_VERSION_1 before validate") which at least lets devices find out which format should config space have, but this is a partial fix: guests should not access config space without acknowledging features since otherwise we'll never be able to change the config space format. To fix, split finalize_features from virtio_finalize_features and call finalize_features with all feature bits before validation, and then - if validation changed any bits - once again after. Since virtio_finalize_features no longer writes out features rename it to virtio_features_ok - since that is what it does: checks that features are ok with the device. As a side effect, this also reduces the amount of hypervisor accesses - we now only acknowledge features once unless we are clearing any features when validating (which is uncommon). IRC I think that this was more or less always the intent in the spec but unfortunately the way the spec is worded does not say this explicitly, I plan to address this at the spec level, too. Acked-by: Jason Wang <jasowang@redhat.com> Cc: stable@vger.kernel.org Fixes:404123c2db
("virtio: allow drivers to validate features") Fixes:2f9a174f91
("virtio: write back F_VERSION_1 before validate") Cc: "Halil Pasic" <pasic@linux.ibm.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
bf52b627cf
commit
573a3228ca
2 changed files with 24 additions and 18 deletions
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@ -167,14 +167,13 @@ void virtio_add_status(struct virtio_device *dev, unsigned int status)
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}
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EXPORT_SYMBOL_GPL(virtio_add_status);
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static int virtio_finalize_features(struct virtio_device *dev)
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/* Do some validation, then set FEATURES_OK */
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static int virtio_features_ok(struct virtio_device *dev)
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{
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int ret = dev->config->finalize_features(dev);
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unsigned status;
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int ret;
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might_sleep();
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if (ret)
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return ret;
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ret = arch_has_restricted_virtio_memory_access();
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if (ret) {
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@ -239,17 +238,6 @@ static int virtio_dev_probe(struct device *_d)
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driver_features_legacy = driver_features;
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}
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/*
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* Some devices detect legacy solely via F_VERSION_1. Write
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* F_VERSION_1 to force LE config space accesses before FEATURES_OK for
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* these when needed.
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*/
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if (drv->validate && !virtio_legacy_is_little_endian()
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&& device_features & BIT_ULL(VIRTIO_F_VERSION_1)) {
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dev->features = BIT_ULL(VIRTIO_F_VERSION_1);
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dev->config->finalize_features(dev);
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}
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if (device_features & (1ULL << VIRTIO_F_VERSION_1))
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dev->features = driver_features & device_features;
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else
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@ -260,13 +248,26 @@ static int virtio_dev_probe(struct device *_d)
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if (device_features & (1ULL << i))
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__virtio_set_bit(dev, i);
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err = dev->config->finalize_features(dev);
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if (err)
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goto err;
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if (drv->validate) {
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u64 features = dev->features;
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err = drv->validate(dev);
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if (err)
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goto err;
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/* Did validation change any features? Then write them again. */
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if (features != dev->features) {
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err = dev->config->finalize_features(dev);
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if (err)
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goto err;
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}
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}
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err = virtio_finalize_features(dev);
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err = virtio_features_ok(dev);
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if (err)
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goto err;
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@ -437,7 +438,11 @@ int virtio_device_restore(struct virtio_device *dev)
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/* We have a driver! */
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virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER);
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ret = virtio_finalize_features(dev);
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ret = dev->config->finalize_features(dev);
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if (ret)
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goto err;
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ret = virtio_features_ok(dev);
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if (ret)
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goto err;
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@ -62,8 +62,9 @@ struct virtio_shm_region {
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* Returns the first 64 feature bits (all we currently need).
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* @finalize_features: confirm what device features we'll be using.
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* vdev: the virtio_device
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* This gives the final feature bits for the device: it can change
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* This sends the driver feature bits to the device: it can change
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* the dev->feature bits if it wants.
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* Note: despite the name this can be called any number of times.
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* Returns 0 on success or error status
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* @bus_name: return the bus name associated with the device (optional)
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* vdev: the virtio_device
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