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qcow: Avoid overflow when taking ceiling of division

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The extra % operation will be slower, but none of these divisions are in
hot paths. They are only used during setup. Many of these operations
take untrusted input from the disk file, so need to be hardened.

BUG=979458
TEST=unit tests still pass

Signed-off-by: Dylan Reid <dgreid@chromium.org>
Change-Id: I0e93c73b345faf643da53ea41bde3349d756bdc7
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/1679891
Reviewed-by: Daniel Verkamp <dverkamp@chromium.org>
Tested-by: kokoro <noreply+kokoro@google.com>
(cherry picked from crosvm commit eecbccc4d9d70b2fd63681a2b3ced6a6aafe81bb)
Signed-off-by: Rob Bradford <robert.bradford@intel.com>
This commit is contained in:
Dylan Reid 2019-06-28 15:19:43 +10:00 committed by Samuel Ortiz
parent 4ba1d2274e
commit 20f8d8d700
1 changed files with 2 additions and 2 deletions
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4
qcow/src/qcow.rs
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@ -1542,12 +1542,12 @@ fn offset_is_cluster_boundary(offset: u64, cluster_bits: u32) -> Result<()> {
// Ceiling of the division of `dividend`/`divisor`.
fn div_round_up_u64(dividend: u64, divisor: u64) -> u64 {
(dividend + divisor - 1) / divisor
dividend / divisor + if dividend % divisor != 0 { 1 } else { 0 }
}
// Ceiling of the division of `dividend`/`divisor`.
fn div_round_up_u32(dividend: u32, divisor: u32) -> u32 {
(dividend + divisor - 1) / divisor
dividend / divisor + if dividend % divisor != 0 { 1 } else { 0 }
}
fn convert_copy<R, W>(reader: &mut R, writer: &mut W, offset: u64, size: u64) -> Result<()>