[Trusty][SRU][PATCH 1/1] btrfs: fix defrag 32-bit integer overflow

[Joseph Salisbury]

From: Justin Maggard <jmaggard10 at gmail.com>

BugLink: http://bugs.launchpad.net/bugs/1324953

When defragging a very large file, the cluster variable can wrap its 32-bit
signed int type and become negative, which eventually gets passed to
btrfs_force_ra() as a very large unsigned long value.  On 32-bit platforms,
this eventually results in an Oops from the SLAB allocator.

Change the cluster and max_cluster signed int variables to unsigned long to
match the readahead functions.  This also allows the min() comparison in
btrfs_defrag_file() to work as intended.

Signed-off-by: Josef Bacik <jbacik at fb.com>
Signed-off-by: Chris Mason <clm at fb.com>
(cherry picked from commit c41570c9d29764f797fa35490d72b7395a0105c3)
Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
---
 fs/btrfs/ioctl.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 9f831bb..043d6cd 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1011,7 +1011,7 @@ out:
 static int cluster_pages_for_defrag(struct inode *inode,
 				    struct page **pages,
 				    unsigned long start_index,
-				    int num_pages)
+				    unsigned long num_pages)
 {
 	unsigned long file_end;
 	u64 isize = i_size_read(inode);
@@ -1169,8 +1169,8 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
 	int defrag_count = 0;
 	int compress_type = BTRFS_COMPRESS_ZLIB;
 	int extent_thresh = range->extent_thresh;
-	int max_cluster = (256 * 1024) >> PAGE_CACHE_SHIFT;
-	int cluster = max_cluster;
+	unsigned long max_cluster = (256 * 1024) >> PAGE_CACHE_SHIFT;
+	unsigned long cluster = max_cluster;
 	u64 new_align = ~((u64)128 * 1024 - 1);
 	struct page **pages = NULL;
 
-- 
2.0.0