misc: return errors from IOMMU address translation instead of panic… - #8023
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rbradford
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The address that is passed from the guest should be treated as
untrusted. Currently an invalid address will panic the VMM. This only
allows the guest to hurt itself, but we shouldn't have the VMM crashing.
Instead let's return an error if possible or invalidate the queue if it
happen during setup.
The data flow from guest to translate_gva/translate_gpa is:
1. Guest writes a raw u64 address into a virtio descriptor in the
shared descriptor table (guest memory).
2. The virtio-queue crate reads this descriptor via read_obj() and
returns the addr field as-is in a GuestAddress — no validation.
3. Device code calls .translate_gva(access_platform, len) on the
GuestAddress.
4. With IOMMU (access_platform is Some): the address is an IOVA that
must be translated to a GPA via the IOMMU mapping table. If the
guest provides an unmapped IOVA, translation returns Err.
Previously, .unwrap() here panicked the VMM.
5. Without IOMMU (access_platform is None): translate_gva is a no-op
(returns self). The raw address flows to GuestMemory::read_obj()
which validates it — out-of-range addresses return
Err(InvalidGuestAddress), so no host memory corruption is possible.
Signed-off-by: Dylan Reid <[email protected]>
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I just updated it to misc - it should now land now. |
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The only thing the guest can do here is crash it's own VMM, but I'd still rather return an error or exit cleanly. WDYT? Luckily all callers were already fallible, so it only took one level of map_err? additions.