virtio: force vring descriptors to be allocated from lowmem
Virtio devices may attempt to add descriptors to a virtqueue from atomic context using GFP_ATOMIC allocation. This is problematic because such allocations can fall outside of the lowmem mapping, causing virt_to_phys to report bogus physical addresses which are subsequently passed to userspace via the buffers for the virtual device. This patch masks out __GFP_HIGH and __GFP_HIGHMEM from the requested flags when allocating descriptors for a virtqueue. If an atomic allocation is requested and later fails, we will return -ENOSPC which will be handled by the driver. Cc: stable@kernel.org Cc: Sasha Levin <levinsasha928@gmail.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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@ -135,6 +135,13 @@ static int vring_add_indirect(struct vring_virtqueue *vq,
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unsigned head;
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int i;
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/*
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* We require lowmem mappings for the descriptors because
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* otherwise virt_to_phys will give us bogus addresses in the
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* virtqueue.
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*/
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gfp &= ~(__GFP_HIGHMEM | __GFP_HIGH);
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desc = kmalloc((out + in) * sizeof(struct vring_desc), gfp);
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if (!desc)
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return -ENOMEM;
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