From ecedda63a6488162c9aad2a99c1ada172340ac7f Mon Sep 17 00:00:00 2001 From: Giuseppe Scrivano Date: Wed, 23 Dec 2020 14:21:28 +0100 Subject: rootless: automatically split userns ranges writing to the id map fails when an extent overlaps multiple mappings in the parent user namespace: $ cat /proc/self/uid_map 0 1000 1 1 100000 65536 $ unshare -U sleep 100 & [1] 1029703 $ printf "0 0 100\n" | tee /proc/$!/uid_map 0 0 100 tee: /proc/1029703/uid_map: Operation not permitted This limitation is particularly annoying when working with rootless containers as each container runs in the rootless user namespace, so a command like: $ podman run --uidmap 0:0:2 --rm fedora echo hi Error: writing file `/proc/664087/gid_map`: Operation not permitted: OCI permission denied would fail since the specified mapping overlaps the first mapping (where the user id is mapped to root) and the second extent with the additional IDs available. Detect such cases and automatically split the specified mapping with the equivalent of: $ podman run --uidmap 0:0:1 --uidmap 1:1:1 --rm fedora echo hi hi A fix has already been proposed for the kernel[1], but even if it accepted it will take time until it is available in a released kernel, so fix it also in pkg/rootless. [1] https://lkml.kernel.org/lkml/20201203150252.1229077-1-gscrivan@redhat.com/ Signed-off-by: Giuseppe Scrivano --- libpod/container_internal_linux.go | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'libpod/container_internal_linux.go') diff --git a/libpod/container_internal_linux.go b/libpod/container_internal_linux.go index cefe12209..bc8f0f932 100644 --- a/libpod/container_internal_linux.go +++ b/libpod/container_internal_linux.go @@ -529,6 +529,13 @@ func (c *Container) generateSpec(ctx context.Context) (*spec.Spec, error) { } } + availableUIDs, availableGIDs, err := rootless.GetAvailableIDMaps() + if err != nil { + return nil, err + } + g.Config.Linux.UIDMappings = rootless.MaybeSplitMappings(g.Config.Linux.UIDMappings, availableUIDs) + g.Config.Linux.GIDMappings = rootless.MaybeSplitMappings(g.Config.Linux.GIDMappings, availableGIDs) + // Hostname handling: // If we have a UTS namespace, set Hostname in the OCI spec. // Set the HOSTNAME environment variable unless explicitly overridden by @@ -536,6 +543,7 @@ func (c *Container) generateSpec(ctx context.Context) (*spec.Spec, error) { // set it to the host's hostname instead. hostname := c.Hostname() foundUTS := false + for _, i := range c.config.Spec.Linux.Namespaces { if i.Type == spec.UTSNamespace && i.Path == "" { foundUTS = true -- cgit v1.2.3-54-g00ecf