Re: [PATCH 1/2] block-backend: Retain permissions after migration

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 11/25/21 14:53, Hanna Reitz wrote:
> After migration, the permissions the guest device wants to impose on its
> BlockBackend are stored in blk->perm and blk->shared_perm.  In
> blk_root_activate(), we take our permissions, but keep all shared
> permissions open by calling `blk_set_perm(blk->perm, BLK_PERM_ALL)`.
> 
> Only afterwards (immediately or later, depending on the runstate) do we
> restrict the shared permissions by calling
> `blk_set_perm(blk->perm, blk->shared_perm)`.  Unfortunately, our first
> call with shared_perm=BLK_PERM_ALL has overwritten blk->shared_perm to
> be BLK_PERM_ALL, so this is a no-op and the set of shared permissions is
> not restricted.
> 
> Fix this bug by saving the set of shared permissions before invoking
> blk_set_perm() with BLK_PERM_ALL and restoring it afterwards.
> 
> Fixes: 5f7772c4d0cf32f4e779fcd5a69ae4dae24aeebf
>        ("block-backend: Defer shared_perm tightening migration
>        completion")
> Reported-by: Peng Liang <liangpeng10@huawei.com>
> Signed-off-by: Hanna Reitz <hreitz@redhat.com>
> ---
>  block/block-backend.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>