pid1: by default make user units inherit their umask from the user manager

This patch changes the way user managers set the default umask for the units it
manages.

Indeed one can expect that if user manager's umask is redefined through PAM
(via /etc/login.defs or pam_umask), all its children including the units it
spawns have their umask set to the new value.

Hence make user units inherit their umask value from their parent instead of
the hard coded value 0022 but allow them to override this value via their unit
file.

Note that reexecuting managers with 'systemctl daemon-reexec' after changing
UMask= has no effect. To take effect managers need to be restarted with
'systemct restart' instead. This behavior was already present before this
patch.

Fixes #6077.

(cherry picked from commit 5e37d1930b41b24c077ce37c6db0e36c745106c7)

Gbp-Pq: Name pid1-by-default-make-user-units-inherit-their-umask-from-.patch

diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml
index fd1755e422a2f652dd7cbfd0d2b5387b14bd97fb..2b57ce0427c2294fe0039d985b9b9467ad8ba25d 100644 (file)
--- a/man/systemd.exec.xml
+++ b/man/systemd.exec.xml
@@ -655,8 +655,13 @@ CapabilityBoundingSet=~CAP_B CAP_C</programlisting>
         <term><varname>UMask=</varname></term>
 
         <listitem><para>Controls the file mode creation mask. Takes an access mode in octal notation. See
-        <citerefentry><refentrytitle>umask</refentrytitle><manvolnum>2</manvolnum></citerefentry> for details. Defaults
-        to 0022.</para></listitem>
+        <citerefentry><refentrytitle>umask</refentrytitle><manvolnum>2</manvolnum></citerefentry> for
+        details. Defaults to 0022 for system units. For units of the user service manager the default value
+        is inherited from the user instance (whose default is inherited from the system service manager, and
+        thus also is 0022). Hence changing the default value of a user instance, either via
+        <varname>UMask=</varname> or via a PAM module, will affect the user instance itself and all user
+        units started by the user instance unless a user unit has specified its own
+        <varname>UMask=</varname>.</para></listitem>
       </varlistentry>
 
       <varlistentry>

diff --git a/src/basic/process-util.c b/src/basic/process-util.c
index 5de366f830e81b3c21815591fe6f565d42eea82f..b84515fb21b951a70b4fa3ec0bd7c6124d6f3760 100644 (file)
--- a/src/basic/process-util.c
+++ b/src/basic/process-util.c
@@ -628,6 +628,23 @@ int get_process_ppid(pid_t pid, pid_t *_ppid) {
         return 0;
 }
 
+int get_process_umask(pid_t pid, mode_t *umask) {
+        _cleanup_free_ char *m = NULL;
+        const char *p;
+        int r;
+
+        assert(umask);
+        assert(pid >= 0);
+
+        p = procfs_file_alloca(pid, "status");
+
+        r = get_proc_field(p, "Umask", WHITESPACE, &m);
+        if (r == -ENOENT)
+                return -ESRCH;
+
+        return parse_mode(m, umask);
+}
+
 int wait_for_terminate(pid_t pid, siginfo_t *status) {
         siginfo_t dummy;
 

diff --git a/src/basic/process-util.h b/src/basic/process-util.h
index 4160af45ba7bcfef5bf9432180c54a29268a22ec..ca9825293c3a2eb1a678df3838301102afc69d07 100644 (file)
--- a/src/basic/process-util.h
+++ b/src/basic/process-util.h
@@ -45,6 +45,7 @@ int get_process_cwd(pid_t pid, char **cwd);
 int get_process_root(pid_t pid, char **root);
 int get_process_environ(pid_t pid, char **environ);
 int get_process_ppid(pid_t pid, pid_t *ppid);
+int get_process_umask(pid_t pid, mode_t *umask);
 
 int wait_for_terminate(pid_t pid, siginfo_t *status);
 

diff --git a/src/core/unit.c b/src/core/unit.c
index 97e1b0004c8955d1af02d046c78e5cd9e7020702..842939c7f4459718a5305787952ce17ecc3d24ab 100644 (file)
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -187,8 +187,16 @@ static void unit_init(Unit *u) {
         if (ec) {
                 exec_context_init(ec);
 
-                ec->keyring_mode = MANAGER_IS_SYSTEM(u->manager) ?
-                        EXEC_KEYRING_SHARED : EXEC_KEYRING_INHERIT;
+                if (MANAGER_IS_SYSTEM(u->manager))
+                        ec->keyring_mode = EXEC_KEYRING_SHARED;
+                else {
+                        ec->keyring_mode = EXEC_KEYRING_INHERIT;
+
+                        /* User manager might have its umask redefined by PAM or UMask=. In this
+                         * case let the units it manages inherit this value by default. They can
+                         * still tune this value through their own unit file */
+                        (void) get_process_umask(getpid_cached(), &ec->umask);
+                }
         }
 
         kc = unit_get_kill_context(u);