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authorMel Gorman <mgorman@suse.de>2012-07-31 16:45:20 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-07-31 18:42:48 -0700
commit737449236240e30a7bbe99f4d5586b8ed1416763 (patch)
tree288fbd38b6c0e250901e218037fae64e79a91f7a
parent192e501b0438bb0e1574179773537f84c4752e25 (diff)
downloadop-kernel-dev-737449236240e30a7bbe99f4d5586b8ed1416763.zip
op-kernel-dev-737449236240e30a7bbe99f4d5586b8ed1416763.tar.gz
swapfile: 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. With reference to this callback, Christoph Hellwig stated "Please just remove the callback entirely. It has no user outside the staging tree and was added clearly against the rules for that staging tree". This would also be my preference but there was not an obvious way of keeping zram in staging/ happy. Signed-off-by: Xiaotian Feng <dfeng@redhat.com> Signed-off-by: Mel Gorman <mgorman@suse.de> Acked-by: Rik van Riel <riel@redhat.com> Cc: Christoph Hellwig <hch@infradead.org> Cc: David S. Miller <davem@davemloft.net> Cc: Eric B Munson <emunson@mgebm.net> Cc: Eric Paris <eparis@redhat.com> Cc: James Morris <jmorris@namei.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Mike Christie <michaelc@cs.wisc.edu> Cc: Neil Brown <neilb@suse.de> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc> Cc: Trond Myklebust <Trond.Myklebust@netapp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/swapfile.c10
1 files changed, 6 insertions, 4 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 7307fc9..63958d6 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -549,7 +549,6 @@ 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)
@@ -560,9 +559,12 @@ static unsigned char swap_entry_free(struct swap_info_struct *p,
nr_swap_pages++;
p->inuse_pages--;
frontswap_invalidate_page(p->type, offset);
- 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;
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