Patch "memfd: Use radix_tree_deref_slot_protected to avoid the warning." has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    memfd: Use radix_tree_deref_slot_protected to avoid the warning.

to the 4.4-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:
     memfd-use-radix_tree_deref_slot_protected-to-avoid-the-warning.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From zhongjiang@huawei.com  Tue Nov 19 05:57:26 2019
From: zhong jiang <zhongjiang@huawei.com>
Date: Mon, 18 Nov 2019 11:26:09 +0800
Subject: memfd: Use radix_tree_deref_slot_protected to avoid the warning.
To: <sashal@kernel.org>, <gregkh@linuxfoundation.org>, <stable@vger.kernel.org>, <willy@infradead.org>
Cc: <linux-mm@kvack.org>, <yangyingliang@huawei.com>
Message-ID: <20191118032610.182862-3-zhongjiang@huawei.com>

From: zhong jiang <zhongjiang@huawei.com>

The commit eb4058d8daf8 ("memfd: Fix locking when tagging pins")
introduces the following warning messages.

*WARNING: suspicious RCU usage in memfd_wait_for_pins*

It is because we still use radix_tree_deref_slot without read_rcu_lock.
We should use radix_tree_deref_slot_protected instead in the case.

Cc: stable@vger.kernel.org
Fixes: eb4058d8daf8 ("memfd: Fix locking when tagging pins")
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 mm/shmem.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1862,7 +1862,7 @@ static void shmem_tag_pins(struct addres
 	spin_lock_irq(&mapping->tree_lock);
 restart:
 	radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
-		page = radix_tree_deref_slot(slot);
+		page = radix_tree_deref_slot_protected(slot, &mapping->tree_lock);
 		if (!page || radix_tree_exception(page)) {
 			if (radix_tree_deref_retry(page))
 				goto restart;


Patches currently in stable-queue which might be from zhongjiang@huawei.com are

queue-4.4/misc-genwqe-should-return-proper-error-value.patch
queue-4.4/memfd-use-radix_tree_deref_slot_protected-to-avoid-the-warning.patch