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| author | Ludovic Courtès <ludo@gnu.org> | 2016-10-18 23:22:03 +0200 |
|---|---|---|
| committer | Ludovic Courtès <ludo@gnu.org> | 2016-10-19 15:54:10 +0200 |
| commit | 7fee5b53973fb4fe049aa0bc5db58093727bdf30 (patch) | |
| tree | b392d7b204098a4dfa3113c7d7fa7f801de11546 | |
| parent | 99df12cd1921dd497bb4fcdd96ee40e358d71e6d (diff) | |
| download | guix-7fee5b53973fb4fe049aa0bc5db58093727bdf30.tar guix-7fee5b53973fb4fe049aa0bc5db58093727bdf30.tar.gz | |
container: Allow 'container-excursion' to the same namespaces.
Before that, 'container-excursion' would call 'setns' even when the
target namespace is the one the caller is already in, which would fail.
* gnu/build/linux-container.scm (container-excursion): Introduce
'source' and 'target'. Compare the result of 'readlink' on these
instead of comparing file descriptors to decide whether to call
'setns'.
* tests/containers.scm ("container-excursion, same namespace"): New test.
| -rw-r--r-- | gnu/build/linux-container.scm | 20 | ||||
| -rw-r--r-- | tests/containers.scm | 9 |
2 files changed, 20 insertions, 9 deletions
diff --git a/gnu/build/linux-container.scm b/gnu/build/linux-container.scm index 91996d06ca..3fccc9addb 100644 --- a/gnu/build/linux-container.scm +++ b/gnu/build/linux-container.scm @@ -291,15 +291,17 @@ return the exit status." (call-with-clean-exit (lambda () (for-each (lambda (ns) - (call-with-input-file (namespace-file (getpid) ns) - (lambda (current-ns-port) - (call-with-input-file (namespace-file pid ns) - (lambda (new-ns-port) - ;; Joining the namespace that the process - ;; already belongs to would throw an error. - (unless (= (port->fdes current-ns-port) - (port->fdes new-ns-port)) - (setns (port->fdes new-ns-port) 0))))))) + (let ((source (namespace-file (getpid) ns)) + (target (namespace-file pid ns))) + ;; Joining the namespace that the process already + ;; belongs to would throw an error so avoid that. + ;; XXX: This /proc interface leads to TOCTTOU. + (unless (string=? (readlink source) (readlink target)) + (call-with-input-file source + (lambda (current-ns-port) + (call-with-input-file target + (lambda (new-ns-port) + (setns (fileno new-ns-port) 0)))))))) ;; It's important that the user namespace is joined first, ;; so that the user will have the privileges to join the ;; other namespaces. Furthermore, it's important that the diff --git a/tests/containers.scm b/tests/containers.scm index bbcff3f51f..698bef3e47 100644 --- a/tests/containers.scm +++ b/tests/containers.scm @@ -162,4 +162,13 @@ (waitpid pid) (zero? result))))))) +(skip-if-unsupported) +(test-equal "container-excursion, same namespaces" + 42 + ;; The parent and child are in the same namespaces. 'container-excursion' + ;; should notice that and avoid calling 'setns' since that would fail. + (container-excursion (getpid) + (lambda () + (primitive-exit 42)))) + (test-end) |