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-rw-r--r--gnu/build/linux-container.scm20
-rw-r--r--tests/containers.scm9
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)