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virtio-devices: iommu: Roll back partial MAP and fix DETACH panic

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A concurrent DETACH between the read-lock check and the write-lock
get_mut().unwrap() in MAP/UNMAP would panic the worker. Replace the
unwrap with a let-else.

A failure on a later endpoint in the per-endpoint MAP loop, or a
DETACH that races the missing-domain branch, must roll back the
external mappings already installed; otherwise domain.mappings
diverges from VFIO state.

Signed-off-by: Rob Bradford <rbradford@meta.com>
Assisted-by: Claude:claude-opus-4-7
This commit is contained in:
Rob Bradford
2026-04-26 22:09:49 +01:00
parent 4d6c7c95c0
commit f77f168532
1 changed files with 33 additions and 26 deletions
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59
virtio-devices/src/iommu.rs
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@@ -121,7 +121,6 @@ const VIRTIO_IOMMU_S_OK: u8 = 0;
const VIRTIO_IOMMU_S_IOERR: u8 = 1;
#[allow(unused)]
const VIRTIO_IOMMU_S_UNSUPP: u8 = 2;
#[allow(unused)]
const VIRTIO_IOMMU_S_DEVERR: u8 = 3;
#[allow(unused)]
const VIRTIO_IOMMU_S_INVAL: u8 = 4;
@@ -510,32 +509,41 @@ impl Request {
return Err(Error::InvalidMapRequest);
}
let mut mapped: Vec<u32> = Vec::new();
let rollback = |mapped: &[u32]| {
for ep in mapped {
if let Some(pmap) = ext_mapping.get(ep) {
let _ = pmap.unmap(req.virt_start, size);
}
}
};
// For viommu all endpoints receive their own VFIO container, as a result
// Each endpoint within the domain needs to be separately mapped, as the
// mapping is done on a per-container level, not a per-domain level
for endpoint in endpoints {
if let Some(ext_map) = ext_mapping.get(&endpoint) {
ext_map
.map(req.virt_start, req.phys_start, size)
.map_err(Error::ExternalMapping)?;
if let Err(e) = ext_map.map(req.virt_start, req.phys_start, size) {
rollback(&mapped);
status = VIRTIO_IOMMU_S_DEVERR;
return Err(Error::ExternalMapping(e));
}
mapped.push(endpoint);
}
}
// Add new mapping associated with the domain
mapping
.domains
.write()
.unwrap()
.get_mut(&domain_id)
.unwrap()
.mappings
.insert(
req.virt_start,
Mapping {
gpa: req.phys_start,
size,
},
);
let mut domains = mapping.domains.write().unwrap();
let Some(domain) = domains.get_mut(&domain_id) else {
rollback(&mapped);
status = VIRTIO_IOMMU_S_NOENT;
return Err(Error::InvalidMapRequestMissingDomain);
};
domain.mappings.insert(
req.virt_start,
Mapping {
gpa: req.phys_start,
size,
},
);
}
VIRTIO_IOMMU_T_UNMAP => {
if desc_size_left != size_of::<VirtioIommuReqUnmap>() {
@@ -614,13 +622,12 @@ impl Request {
}
}
// Remove all mappings associated with the domain within the requested range
mapping
.domains
.write()
.unwrap()
.get_mut(&domain_id)
.unwrap()
let mut domains = mapping.domains.write().unwrap();
let Some(domain) = domains.get_mut(&domain_id) else {
status = VIRTIO_IOMMU_S_INVAL;
return Err(Error::InvalidUnmapRequestMissingDomain);
};
domain
.mappings
.retain(|&x, _| x < req.virt_start || x > req.virt_end);
}