Re: [PATCH v3 14/15] iommufd: vfio container FD ioctl compatibility

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> +	down_read(&ioas->iopt.iova_rwsem);
> +	info.flags = VFIO_IOMMU_INFO_PGSIZES;
> +	info.iova_pgsizes = iommufd_get_pagesizes(ioas);
> +	info.cap_offset = 0;

The iommufd_get_pagesizes() obtains the domains_rwsem and cannot be
called under the iova_rwsem due to lock odering.

The test suite already covers this, but it turns out my test
environment had lockdep disabled since it hits a Intel iommu lockdep
splat on boot starting in v6.1-rc1 :\ Syzkaller found it because it
runs the VM with different options and avoids the boot splat.

@@ -371,11 +371,11 @@ static int iommufd_vfio_iommu_get_info(struct iommufd_ctx *ictx,
        if (IS_ERR(ioas))
                return PTR_ERR(ioas);
 
-       down_read(&ioas->iopt.iova_rwsem);
        info.flags = VFIO_IOMMU_INFO_PGSIZES;
        info.iova_pgsizes = iommufd_get_pagesizes(ioas);
        info.cap_offset = 0;
 
+       down_read(&ioas->iopt.iova_rwsem);
        total_cap_size = sizeof(info);
        for (i = 0; i != ARRAY_SIZE(fill_fns); i++) {
                int cap_size;

Jason



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