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virtio-devices: rng: Preserve byte count on mid-chain errors

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When address translation or the entropy read fails mid-chain the
handler reset total_len to zero before breaking out of the loop.
If earlier descriptors in the same chain were already filled, the
used ring entry under-reports the bytes actually written to guest
memory. Drop the reset so the used length reflects reality.

Signed-off-by: Rob Bradford <rbradford@meta.com>
Assisted-by: Claude:claude-opus-4-6
This commit is contained in:
Rob Bradford
2026-05-06 12:52:24 +01:00
parent aee4fd6010
commit 5702e9751c
1 changed files with 0 additions and 4 deletions
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4
virtio-devices/src/rng.rs
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@@ -60,8 +60,6 @@ impl RngEpollHandler {
let mut used_descs = false;
while let Some(mut desc_chain) = queue.pop_descriptor_chain(self.mem.memory()) {
// virtio-rng has no status byte; on any error along the chain
// report a used length of 0 to indicate failure.
let mut total_len: usize = 0;
while let Some(desc) = desc_chain.next() {
if !desc.is_write_only() {
@@ -78,7 +76,6 @@ impl RngEpollHandler {
Ok(a) => a,
Err(e) => {
warn!("Failed to translate descriptor address: {e}");
total_len = 0;
break;
}
};
@@ -90,7 +87,6 @@ impl RngEpollHandler {
Ok(written) => total_len += written,
Err(e) => {
warn!("Failed to read entropy into descriptor: {e}");
total_len = 0;
break;
}
}