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Check virtio-fs DAX mappings against the DAX window - #537
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To handle SHMEM_MAP and SHMEM_UNMAP requests from the backend, VuFs repeats the mmap() calls of the DaxRegion implementation of ArcMemPages. Call the DaxRegion methods instead, so that the built-in virtio-fs device and the vhost-user one change the DAX window in one place. Signed-off-by: Changyuan Lyu <changyuanl@google.com>
The DaxRegion implementation of ArcMemPages maps a file to, or unmaps, a range of the DAX window with MAP_FIXED, but does not check that the range is within the window. The guest gives the range in FUSE_SETUPMAPPING and FUSE_REMOVEMAPPING requests to the built-in virtio-fs device, and the vhost-user backend gives it in SHMEM_MAP and SHMEM_UNMAP requests to the vhost-user virtio-fs device. Either could replace any memory mapping of the VMM process, e.g. with the contents of a file it controls. Fail a range outside the DAX window with a new InvalidDaxRange error, which is EINVAL to the guest. Fixes: b852e8c ("feat(fs): DAX support for built-in virtio fs") Fixes: 359ab26 ("feat(fs): support virtio-fs DAX mapping") Signed-off-by: Changyuan Lyu <changyuanl@google.com>
VuFs panics at a backend request other than SHMEM_MAP and SHMEM_UNMAP, and stops the device when a SHMEM request fails, e.g. with a range outside the DAX window. It also replies to every request, even if the backend did not set VHOST_USER_NEED_REPLY. Return an error at an unsupported request instead of panicking: its payload is unknown, so the backend channel cannot go on. When a SHMEM request fails, log the error and reply a non-zero value, as the vhost-user spec requires, and reply only if the backend asks for it. Fixes: 359ab26 ("feat(fs): support virtio-fs DAX mapping") Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Coverage Report for CI Build 42728235790Coverage increased (+0.6%) to 40.356%Details
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Coverage RegressionsNo coverage regressions found. Coverage Stats
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The built-in and vhost-user virtio-fs devices map a file to, or unmap, a range
of the DAX window with
MAP_FIXED, without checking that the range is withinthe window. A guest (with
FUSE_SETUPMAPPINGorFUSE_REMOVEMAPPING) or avhost-user backend (with
SHMEM_MAPorSHMEM_UNMAP) can replace any memorymapping of the VMM process. In addition,
VuFspanics at an unknown backendrequest, stops the device when a
SHMEMrequest fails, and replies even if thebackend did not ask for a reply.
SHMEM_MAPandSHMEM_UNMAPrequests withDaxRegion, sothat the built-in and vhost-user devices change the DAX window in one place.
returning
EINVALto the guest otherwise.SHMEMrequest fails, log the error and reply a non-zero value withoutstopping the device; reply only when
VHOST_USER_NEED_REPLYis set.Every commit passes
cargo +nightly fmt --check,cargo clippy --all-targets -D warningson x86_64-unknown-linux-gnu/musl, aarch64-unknown-linux-gnu andaarch64-apple-darwin, and
cargo test --workspacelocally.