[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>

diff --git a/kernel/power/disk.c b/kernel/power/disk.c
index 664eb0469b6e18230f3daf84fcf78ed09e8f0bcf..88beec6dcd112534dc59214d6925bf811933d4d5 100644 (file)
--- 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();