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Extract FileMode from host path if possible #960

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Extract FileMode from host path if possible #960

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22 changes: 22 additions & 0 deletions internal/edits/device.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,9 +17,13 @@
package edits

import (
"os"

"tags.cncf.io/container-device-interface/pkg/cdi"
"tags.cncf.io/container-device-interface/specs-go"

"github.com/opencontainers/runc/libcontainer/devices"

"github.com/NVIDIA/nvidia-container-toolkit/internal/discover"
)

Expand Down Expand Up @@ -49,13 +53,31 @@ func (d device) toSpec() (*specs.DeviceNode, error) {
// Since the behaviour for HostPath == "" and HostPath == Path are equivalent, we clear HostPath
// if it is equal to Path to ensure compatibility with the widest range of specs.
hostPath := d.HostPath

if hostPath == d.Path {
hostPath = ""
}
s := specs.DeviceNode{
HostPath: hostPath,
Path: d.Path,
FileMode: d.getFileMode(),
}

return &s, nil
}

// getFileMode returns the filemode of the host device node associated with the discovered device.
// If this fails, a nil filemode is returned.
func (d device) getFileMode() *os.FileMode {
path := d.HostPath
if path == "" {
path = d.Path
}
dn, err := devices.DeviceFromPath(path, "rwm")
if err != nil {
// return nil, fmt.Errorf("failed to get device information for %q: %w", path, err)
return nil
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To what will nil translate to in the spec? => 0 ?

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@elezar elezar Mar 5, 2025 •
edited
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nil would be the current behaviour. In the case of runc this is filled in by the runtime and read from the host. In the case of kata, this would be 0 as you've observed.

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The interface is the CDI spec, so how does runc know this value is nil? It is not encoded in the CDI spec.

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@elezar elezar Mar 6, 2025 •
edited
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Actually, maybe runc is not the correct reference here. For regular devices, a higher-level runtime such as containerd also extracts the FileMode (see https://github.com/containerd/containerd/blob/9deb0b8f748ee038dfd48c51d7aee6b55e34e9c1/pkg/oci/utils_unix.go#L142). This is not done for CDI devices since the code from https://github.com/cncf-tags/container-device-interface/blob/012c8be38d9444f08b7e6eeedbcddd733adf8632/pkg/cdi/container-edits_unix.go#L60 is used for this instead.

This means that for OCI devices created from a CDI spec, this field is nil if unspecified, whereas for "regular" devices this field is populated from the device node on the host.

@klihub do you know why we elected to not add information other than the Major and Minor numbers to the devices in CDI?

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@elezar Do you mean what is the reason for not filling in any other missing information wrt. the CDI Spec DeviceNode than type, major, and minor ? TBH, I don't recall any specifics, but I suspect it's only because that's the minimum working implementation.

}

return &dn.FileMode
}
174 changes: 174 additions & 0 deletions vendor/github.com/opencontainers/runc/libcontainer/devices/device.go
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119 changes: 119 additions & 0 deletions vendor/github.com/opencontainers/runc/libcontainer/devices/device_unix.go
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1 change: 1 addition & 0 deletions vendor/modules.txt
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Original file line number Diff line number Diff line change
Expand Up @@ -36,6 +36,7 @@ github.com/google/uuid
github.com/moby/sys/symlink
# github.com/opencontainers/runc v1.2.5
## explicit; go 1.22
github.com/opencontainers/runc/libcontainer/devices
github.com/opencontainers/runc/libcontainer/dmz
github.com/opencontainers/runc/libcontainer/system
github.com/opencontainers/runc/libcontainer/utils
Expand Down