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qcow: Calculate the max refcounts as a u64

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u32's get multiplied together and can overflow. A usize was being
returned, make everything a u64 to make sure it fits.

Change-Id: I87071d294f4e62247c9ae72244db059a7b528b62
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1651459
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
This commit is contained in:
Dylan Reid 2019-06-09 16:42:59 -07:00 committed by Commit Bot
parent cae80e321a
commit 21c941786e
1 changed files with 7 additions and 6 deletions
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13
qcow/src/qcow.rs
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@ -295,11 +295,12 @@ impl QcowHeader {
} }
} }
fn max_refcount_clusters(refcount_order: u32, cluster_size: u32, num_clusters: u32) -> usize { fn max_refcount_clusters(refcount_order: u32, cluster_size: u32, num_clusters: u32) -> u64 {
let refcount_bytes = (0x01u32 << refcount_order) / 8; // Use u64 as the product of the u32 inputs can overflow.
let for_data = div_round_up_u32(num_clusters * refcount_bytes, cluster_size); let refcount_bytes = (0x01 << refcount_order as u64) / 8;
let for_refcounts = div_round_up_u32(for_data * refcount_bytes, cluster_size); let for_data = div_round_up_u64(num_clusters as u64 * refcount_bytes, cluster_size as u64);
for_data as usize + for_refcounts as usize let for_refcounts = div_round_up_u64(for_data * refcount_bytes, cluster_size as u64);
for_data + for_refcounts
} }
/// Represents a qcow2 file. This is a sparse file format maintained by the qemu project. /// Represents a qcow2 file. This is a sparse file format maintained by the qemu project.
@ -419,7 +420,7 @@ impl QcowFile {
header.refcount_order, header.refcount_order,
cluster_size as u32, cluster_size as u32,
(num_clusters + l1_clusters + num_l2_clusters + header_clusters) as u32, (num_clusters + l1_clusters + num_l2_clusters + header_clusters) as u32,
) as u64; );
let refcount_block_entries = cluster_size / refcount_bytes; let refcount_block_entries = cluster_size / refcount_bytes;
let refcounts = RefCount::new( let refcounts = RefCount::new(
&mut raw_file, &mut raw_file,