linux-kernel - [PATCH v2 2/2] PM: hibernate: Fix the exclusive get block device in test

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Date:   Wed,  6 Sep 2023 12:18:52 +0800
From:   Chen Yu <yu.c.chen@...el.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Chenzhou Feng <chenzhoux.feng@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>,
        Chen Yu <yu.c.chen@...el.com>,
        syzbot+38d04642cea49f3a3d2e@...kaller.appspotmail.com
Subject: [PATCH v2 2/2] PM: hibernate: Fix the exclusive get block device in test_resume mode

commit 5904de0d735b ("PM: hibernate: Do not get block device exclusively
in test_resume mode") fixes a hibernation issue under test_resume mode.
That commit is supposed to open the block device in non-exclusive mode
when in test_resume. However the code did the opposite, which is against
its description.

In summary, the swap device is only opened exclusively by swsusp_check()
with its corresponding *close(), and must be in non test_resume mode.
This is to avoid the race condition that different processes scribble the
device at the same time. All the other cases should use non-exclusive mode.

Fix it by really disabling exclusive mode under test_resume.

Fixes: 5904de0d735b ("PM: hibernate: Do not get block device exclusively in test_resume mode")
Reported-by: syzbot+38d04642cea49f3a3d2e@...kaller.appspotmail.com
Closes: https://lore.kernel.org/lkml/000000000000761f5f0603324129@google.com/
Reported-by: Pengfei Xu <pengfei.xu@...el.com>
Signed-off-by: Chen Yu <yu.c.chen@...el.com>
---
 kernel/power/hibernate.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 2b4a946a6ff5..8d35b9f9aaa3 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -786,9 +786,9 @@ int hibernate(void)
 	unlock_device_hotplug();
 	if (snapshot_test) {
 		pm_pr_dbg("Checking hibernation image\n");
-		error = swsusp_check(snapshot_test);
+		error = swsusp_check(false);
 		if (!error)
-			error = load_image_and_restore(snapshot_test);
+			error = load_image_and_restore(false);
 	}
 	thaw_processes();
 
@@ -945,14 +945,14 @@ static int software_resume(void)
 	pm_pr_dbg("Looking for hibernation image.\n");
 
 	mutex_lock(&system_transition_mutex);
-	error = swsusp_check(false);
+	error = swsusp_check(true);
 	if (error)
 		goto Unlock;
 
 	/* The snapshot device should not be opened while we're running */
 	if (!hibernate_acquire()) {
 		error = -EBUSY;
-		swsusp_close(false);
+		swsusp_close(true);
 		goto Unlock;
 	}
 
@@ -973,7 +973,7 @@ static int software_resume(void)
 		goto Close_Finish;
 	}
 
-	error = load_image_and_restore(false);
+	error = load_image_and_restore(true);
 	thaw_processes();
  Finish:
 	pm_notifier_call_chain(PM_POST_RESTORE);
@@ -987,7 +987,7 @@ static int software_resume(void)
 	pm_pr_dbg("Hibernation image not present or could not be loaded.\n");
 	return error;
  Close_Finish:
-	swsusp_close(false);
+	swsusp_close(true);
 	goto Finish;
 }
 
-- 
2.25.1