Patch "mm: khugepaged: fix radix tree node leak in shmem collapse error path" has been added to the 4.9-stable tree

Patch "mm: khugepaged: fix radix tree node leak in shmem collapse error path" has been added to the 4.9-stable tree

[gregkh]

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

    mm: khugepaged: fix radix tree node leak in shmem collapse error path

to the 4.9-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:
     mm-khugepaged-fix-radix-tree-node-leak-in-shmem-collapse-error-path.patch
and it can be found in the queue-4.9 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 59749e6ce53735d8b696763742225f126e94603f Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Mon, 12 Dec 2016 16:43:35 -0800
Subject: mm: khugepaged: fix radix tree node leak in shmem collapse error path

From: Johannes Weiner <hannes@cmpxchg.org>

commit 59749e6ce53735d8b696763742225f126e94603f upstream.

The radix tree counts valid entries in each tree node.  Entries stored
in the tree cannot be removed by simpling storing NULL in the slot or
the internal counters will be off and the node never gets freed again.

When collapsing a shmem page fails, restore the holes that were filled
with radix_tree_insert() with a proper radix tree deletion.

Fixes: f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages")
Link: http://lkml.kernel.org/r/20161117191138.22769-3-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Jan Kara <jack@suse.cz>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <mawilcox@linuxonhyperv.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 mm/khugepaged.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1525,9 +1525,11 @@ tree_unlocked:
 			if (!page || iter.index < page->index) {
 				if (!nr_none)
 					break;
-				/* Put holes back where they were */
-				radix_tree_replace_slot(slot, NULL);
 				nr_none--;
+				/* Put holes back where they were */
+				radix_tree_delete(&mapping->page_tree,
+						  iter.index);
+				slot = radix_tree_iter_next(&iter);
 				continue;
 			}
 


Patches currently in stable-queue which might be from hannes@cmpxchg.org are

queue-4.9/mm-khugepaged-fix-radix-tree-node-leak-in-shmem-collapse-error-path.patch
queue-4.9/mm-khugepaged-close-use-after-free-race-during-shmem-collapsing.patch