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Subject[PATCH -mmotm 29/30] fix null pointer deref in swap_entry_free
From ea7b13006f42f7dcadd1bfb874d5e525b4c259e3 Mon Sep 17 00:00:00 2001
From: Xiaotian Feng <dfeng@redhat.com>
Date: Tue, 13 Jul 2010 13:44:08 +0800
Subject: [PATCH 29/30] fix null pointer deref in swap_entry_free

Commit b3a27d uses p->bdev->bd_disk, this will lead a null pointer
deref with swap over nfs.

Signed-off-by: Xiaotian Feng <dfeng@redhat.com>
---
mm/swapfile.c | 9 +++++----
1 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index d8a05e4..3eb53fc 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -577,7 +577,6 @@ 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)
@@ -587,9 +586,11 @@ 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;
--
1.7.1.1


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