From 164bd929f1c85026f21ed493d11d3b4d1b94421d Mon Sep 17 00:00:00 2001
From: Jan Synacek <jsynacek@redhat.com>
Date: Wed, 17 Jan 2018 09:13:24 +0100
Subject: [PATCH] automount: ack automount requests even when already mounted

If a process accesses an autofs filesystem while systemd is in the
middle of starting the mount unit on top of it, it is possible for the
autofs_ptype_missing_direct request from the kernel to be received after
the mount unit has been fully started:

  systemd forks and execs mount             ...
            ...                     access autofs, blocks
  mount exits                               ...
  systemd receives SIGCHLD                  ...
            ...                     kernel sends request
  systemd receives request                  ...

systemd needs to respond to this request, otherwise the kernel will
continue to block access to the mount point.

(cherry picked from commit e7d54bf58789545a9eb0b3964233defa0b007318)

Resolves: #1535135
---
 src/core/automount.c | 28 ++++++++++++++++------------
 1 file changed, 16 insertions(+), 12 deletions(-)

diff --git a/src/core/automount.c b/src/core/automount.c
index 4e066613d..9e05963e9 100644
--- a/src/core/automount.c
+++ b/src/core/automount.c
@@ -692,7 +692,7 @@ static int automount_start_expire(Automount *a) {
                         automount_dispatch_expire, a);
 }
 
-static void automount_enter_runnning(Automount *a) {
+static void automount_enter_running(Automount *a) {
         _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
         struct stat st;
         int r;
@@ -718,18 +718,22 @@ static void automount_enter_runnning(Automount *a) {
                 goto fail;
         }
 
-        if (!S_ISDIR(st.st_mode) || st.st_dev != a->dev_id)
+        /* The mount unit may have been explicitly started before we got the
+         * autofs request. Ack it to unblock anything waiting on the mount point. */
+        if (!S_ISDIR(st.st_mode) || st.st_dev != a->dev_id) {
                 log_unit_info(UNIT(a)->id,
                               "%s's automount point already active?", UNIT(a)->id);
-        else {
-                r = manager_add_job(UNIT(a)->manager, JOB_START, UNIT_TRIGGER(UNIT(a)),
-                                    JOB_REPLACE, true, &error, NULL);
-                if (r < 0) {
-                        log_unit_warning(UNIT(a)->id,
-                                         "%s failed to queue mount startup job: %s",
-                                         UNIT(a)->id, bus_error_message(&error, r));
-                        goto fail;
-                }
+                automount_send_ready(a, a->tokens, 0);
+                return;
+        }
+
+        r = manager_add_job(UNIT(a)->manager, JOB_START, UNIT_TRIGGER(UNIT(a)),
+                        JOB_REPLACE, true, &error, NULL);
+        if (r < 0) {
+                log_unit_warning(UNIT(a)->id,
+                                "%s failed to queue mount startup job: %s",
+                                UNIT(a)->id, bus_error_message(&error, r));
+                goto fail;
         }
 
         r = automount_start_expire(a);
@@ -953,7 +957,7 @@ static int automount_dispatch_io(sd_event_source *s, int fd, uint32_t events, vo
                         goto fail;
                 }
 
-                automount_enter_runnning(a);
+                automount_enter_running(a);
                 break;
 
         case autofs_ptype_expire_direct: