virtio: acknowledge all features before access
stable inclusion from stable-v5.10.106 commit 573a3228ca3268441ce334251cb9fec0d69ca574 bugzilla: https://gitee.com/openeuler/kernel/issues/I573US Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=573a3228ca3268441ce334251cb9fec0d69ca574 -------------------------------- commit 4fa59ede 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 commit 404123c2 ("virtio: allow drivers to validate features") with fallout in at least block and net. We have a partial work-around in commit 2f9a174f ("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: NJason Wang <jasowang@redhat.com> Cc: stable@vger.kernel.org Fixes: 404123c2 ("virtio: allow drivers to validate features") Fixes: 2f9a174f ("virtio: write back F_VERSION_1 before validate") Cc: "Halil Pasic" <pasic@linux.ibm.com> Signed-off-by: NMichael S. Tsirkin <mst@redhat.com> Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: NYu Liao <liaoyu15@huawei.com> Reviewed-by: NWei Li <liwei391@huawei.com> Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
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