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Date: Fri, 9 Sep 2011 12:00:54 +0100
From: Mel Gorman <mgorman@...e.de>
To: Linux-MM <linux-mm@...ck.org>
Cc: Linux-Netdev <netdev@...r.kernel.org>,
Linux-NFS <linux-nfs@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
David Miller <davem@...emloft.net>,
Trond Myklebust <Trond.Myklebust@...app.com>,
Neil Brown <neilb@...e.de>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Mel Gorman <mgorman@...e.de>
Subject: [PATCH 10/10] Avoid dereferencing bd_disk during swap_entry_free for network storage
Commit [b3a27d: swap: Add swap slot free callback to
block_device_operations] dereferences p->bdev->bd_disk but this is a
NULL dereference if using swap-over-NFS. This patch checks SWP_BLKDEV
on the swap_info_struct before dereferencing.
Signed-off-by: Xiaotian Feng <dfeng@...hat.com>
Signed-off-by: Mel Gorman <mgorman@...e.de>
---
mm/swapfile.c | 9 +++++----
1 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 806b994..8b85a88 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -547,7 +547,6 @@ static unsigned char swap_entry_free(struct swap_info_struct *p,
/* free if no reference */
if (!usage) {
- struct gendisk *disk = p->bdev->bd_disk;
if (offset < p->lowest_bit)
p->lowest_bit = offset;
if (offset > p->highest_bit)
@@ -557,9 +556,11 @@ static unsigned char swap_entry_free(struct swap_info_struct *p,
swap_list.next = p->type;
nr_swap_pages++;
p->inuse_pages--;
- if ((p->flags & SWP_BLKDEV) &&
- disk->fops->swap_slot_free_notify)
- disk->fops->swap_slot_free_notify(p->bdev, offset);
+ if (p->flags & SWP_BLKDEV) {
+ struct gendisk *disk = p->bdev->bd_disk;
+ if (disk->fops->swap_slot_free_notify)
+ disk->fops->swap_slot_free_notify(p->bdev, offset);
+ }
}
return usage;
--
1.7.3.4
--
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