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sys: simplify RunningInUserNS to original implementation

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Given that we're only interested in detecting if userns is
enabled, and no further details about the mapping, we can
revert this function to go back to its original implementation
in github.com/lxc/lxd/shared/util.go

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This commit is contained in:
Sebastiaan van Stijn 2020-05-04 14:45:37 +02:00
parent 6a9b94927f
commit 76c62f2722
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GPG Key ID: 76698F39D527CE8C
1 changed files with 17 additions and 3 deletions
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20
sys/userns_linux.go
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@ -17,22 +17,36 @@
package sys
import (
"github.com/opencontainers/runc/libcontainer/user"
"bufio"
"fmt"
"os"
)
// RunningInUserNS detects whether we are currently running in a user namespace.
// Originally copied from github.com/lxc/lxd/shared/util.go
func RunningInUserNS() bool {
uidmap, err := user.CurrentProcessUIDMap()
file, err := os.Open("/proc/self/uid_map")
if err != nil {
// This kernel-provided file only exists if user namespaces are supported
return false
}
defer file.Close()
buf := bufio.NewReader(file)
l, _, err := buf.ReadLine()
if err != nil {
return false
}
line := string(l)
var a, b, c int64
fmt.Sscanf(line, "%d %d %d", &a, &b, &c)
/*
* We assume we are in the initial user namespace if we have a full
* range - 4294967295 uids starting at uid 0.
*/
if len(uidmap) == 1 && uidmap[0].ID == 0 && uidmap[0].ParentID == 0 && uidmap[0].Count == 4294967295 {
if a == 0 && b == 0 && c == 4294967295 {
return false
}
return true