virtio_balloon: fix towards_target when deflating balloon
Both v and vb->num_pages are u32 and unsigned int respectively. If v is less than vb->num_pages (and it is, when deflating the balloon), the result is a very large 32-bit number. Since we're returning a s64, instead of getting the same negative number we desire, we get a very large positive number. This handles the case where v < vb->num_pages and ensures we get a small, negative, s64 as the result. Rusty: please push this for 2.6.27-rc4. It's probably appropriate for the stable tree too as it will cause an unexpected OOM when ballooning. Signed-off-by: Anthony Liguori <aliguori@us.ibm.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (simplified)
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@ -158,7 +158,7 @@ static inline s64 towards_target(struct virtio_balloon *vb)
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vb->vdev->config->get(vb->vdev,
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offsetof(struct virtio_balloon_config, num_pages),
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&v, sizeof(v));
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return v - vb->num_pages;
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return (s64)v - vb->num_pages;
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}
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static void update_balloon_size(struct virtio_balloon *vb)
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