[PATCH] swsusp: add locking to software_resume

It is trying to protect swsusp_resume_device and software_resume() from two
users banging it from userspace at the same time.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 9 insertions, 1 deletions

diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index 664eb0469b6e..88beec6dcd11 100644
--- a/kernel/power/disk.c
+++ b/kernel/power/disk.c
@@ -233,9 +233,12 @@ static int software_resume(void)
 {
         int error;
 
+        down(&pm_sem);
         if (!swsusp_resume_device) {
-                if (!strlen(resume_file))
+                if (!strlen(resume_file)) {
+                        up(&pm_sem);
                         return -ENOENT;
+                }
                 swsusp_resume_device = name_to_dev_t(resume_file);
                 pr_debug("swsusp: Resume From Partition %s\n", resume_file);
         } else {
@@ -248,6 +251,7 @@ static int software_resume(void)
                  * FIXME: If noresume is specified, we need to find the partition
                  * and reset it back to normal swap space.
                  */
+                up(&pm_sem);
                 return 0;
         }
 
@@ -284,6 +288,8 @@ static int software_resume(void)
  Cleanup:
         unprepare_processes();
  Done:
+        /* For success case, the suspend path will release the lock */
+        up(&pm_sem);
         pr_debug("PM: Resume from disk failed.\n");
         return 0;
 }
@@ -390,7 +396,9 @@ static ssize_t resume_store(struct subsystem * subsys, const char * buf, size_t
         if (sscanf(buf, "%u:%u", &maj, &min) == 2) {
                 res = MKDEV(maj,min);
                 if (maj == MAJOR(res) && min == MINOR(res)) {
+                        down(&pm_sem);
                         swsusp_resume_device = res;
+                        up(&pm_sem);
                         printk("Attempting manual resume\n");
                         noresume = 0;
                         software_resume();