3 files changed, 21 insertions, 15 deletions

diff --git a/gnu/build/linux-container.scm b/gnu/build/linux-container.scm
index 3e5158c2fd7..b6f8563f7d0 100644
--- a/gnu/build/linux-container.scm
+++ b/gnu/build/linux-container.scm
@@ -30,6 +30,7 @@
             unprivileged-user-namespace-supported?
             setgroups-supported?
             %namespaces
+            %writable-/tmp
             run-container
             call-with-container
             container-excursion
@@ -387,6 +388,16 @@ if there are no child processes left."
       (+ 128 (or (status:term-sig status)
                  (status:stop-sig status)))))
 
+(define %writable-/tmp
+  ;; Writable and volatile /tmp.
+  (file-system
+    (device "none")
+    (mount-point "/tmp")
+    (type "tmpfs")
+    (flags '(no-suid no-dev))
+    (options "mode=755,size=10%")
+    (check? #f)))
+
 (define* (call-with-container mounts thunk #:key (namespaces %namespaces)
                               (host-uids 1) (guest-uid 0) (guest-gid 0)
                               (lock-mounts? #t)
diff --git a/guix/scripts/environment.scm b/guix/scripts/environment.scm
index 429a5a296f7..41353e33053 100644
--- a/guix/scripts/environment.scm
+++ b/guix/scripts/environment.scm
@@ -40,6 +40,7 @@
   #:autoload   (ice-9 ftw) (scandir)
   #:autoload   (gnu build install) (evaluate-populate-directive)
   #:autoload   (gnu build linux-container) (call-with-container %namespaces
+                                            %writable-/tmp
                                             user-namespace-supported?
                                             unprivileged-user-namespace-supported?
                                             setgroups-supported?)
@@ -771,13 +772,6 @@ added to the container.
 
 Preserve environment variables whose name matches the one of the regexps in
 WHILE-LIST."
-  (define tmpfs
-    (file-system
-      (device "none")
-      (mount-point "/tmp")
-      (type "tmpfs")
-      (check? #f)))
-
   (define (optional-mapping->fs mapping)
     (and (file-exists? (file-system-mapping-source mapping))
          (file-system-mapping->bind-mount mapping)))
@@ -875,9 +869,12 @@ WHILE-LIST."
                       (writable? #f)))
                    reqs)))
             (file-systems (append %container-file-systems
-                                  (list tmpfs        ; RW /tmp
+                                  (list %writable-/tmp
                                         (file-system ; RW /run
-                                          (inherit tmpfs)
+                                          (device "none")
+                                          (type "tmpfs")
+                                          (options "size=10%,mode=700")
+                                          (check? #f)
                                           (mount-point
                                            (string-append "/run/user/"
                                                           (number->string uid))))
diff --git a/guix/scripts/home.scm b/guix/scripts/home.scm
index a4b8cc01e70..ae003816f92 100644
--- a/guix/scripts/home.scm
+++ b/guix/scripts/home.scm
@@ -38,7 +38,9 @@
                                      group-entry
                                      write-passwd
                                      write-group)
-  #:autoload   (gnu build linux-container) (call-with-container %namespaces)
+  #:autoload   (gnu build linux-container) (call-with-container
+                                            %namespaces
+                                            %writable-/tmp)
   #:use-module ((gnu system) #:select (operating-system?
                                        operating-system-user-services))
   #:autoload   (gnu system linux-container) (eval/container)
@@ -353,11 +355,7 @@ immediately.  Return the exit status of the process in the container."
    #:namespaces (if network?
                     (delq 'net %namespaces)       ; share host network
                     %namespaces)
-   #:mounts (list (file-system                    ;writable /tmp
-                    (device "none")
-                    (mount-point "/tmp")
-                    (type "tmpfs")
-                    (check? #f))
+   #:mounts (list %writable-/tmp
                   (file-system
                     (device "none")
                     (mount-point