Patch "md: be careful not lot leak internal curr_resync value into metadata. -- (all)" has been added to the 4.8-stable tree

This is a note to let you know that I've just added the patch titled

md: be careful not lot leak internal curr_resync value into metadata. -- (all)

to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
md-be-careful-not-lot-leak-internal-curr_resync-value-into-metadata.-all.patch
and it can be found in the queue-4.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: NeilBrown <[email protected]>
Date: Fri, 28 Oct 2016 15:59:41 +1100
Subject: md: be careful not lot leak internal curr_resync value into metadata. -- (all)

From: NeilBrown <[email protected]>

commit 1217e1d1999ed6c9c1e1b1acae0a74ab70464ae2 upstream.

mddev->curr_resync usually records where the current resync is up to, but during the starting phase it has some "magic" values.

1 - means that the array is trying to start a resync, but has yielded
to another array which shares physical devices, and also needs to start a resync
2 - means the array is trying to start resync, but has found another
array which shares physical devices and has already started resync.

3 - means that resync has commensed, but it is possible that nothing
has actually been resynced yet.

It is important that this value not be visible to user-space and particularly that it doesn't get written to the metadata, as the resync or recovery checkpoint. In part, this is because it may be slightly higher than the correct value, though this is very rare. In part, because it is not a multiple of 4K, and some devices only support 4K aligned accesses.

There are two places where this value is propagates into either ->curr_resync_completed or ->recovery_cp or ->recovery_offset. These currently avoid the propagation of values 1 and 3, but will allow 3 to leak through.

Change them to only propagate the value if it is > 3.

As this can cause an array to fail, the patch is suitable for -stable.

---
 drivers/md/md.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -8120,14 +8120,14 @@ void md_do_sync(struct md_thread *thread
 
 	if (!test_bit(MD_RECOVERY_RESHAPE, &mddev->recovery) &&
 	    !test_bit(MD_RECOVERY_INTR, &mddev->recovery) &&
-	    mddev->curr_resync > 2) {
+	    mddev->curr_resync > 3) {
 		mddev->curr_resync_completed = mddev->curr_resync;
 		sysfs_notify(&mddev->kobj, NULL, "sync_completed");
 	}
 	mddev->pers->sync_request(mddev, max_sectors, &skipped);
 
 	if (!test_bit(MD_RECOVERY_CHECK, &mddev->recovery) &&
-	    mddev->curr_resync > 2) {
+	    mddev->curr_resync > 3) {
 		if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery)) {
 			if (test_bit(MD_RECOVERY_INTR, &mddev->recovery)) {
 				if (mddev->curr_resync >= mddev->recovery_cp) {

Patches currently in stable-queue which might be from [email protected] are

queue-4.8/md-be-careful-not-lot-leak-internal-curr_resync-value-into-metadata.-all.patch