btrfs: zero out left over bytes after processing compression streams

Don Bailey noticed that our page zeroing for compression at end-io time
isn't complete.  This reworks a patch from Linus to push the zeroing
into the zlib and lzo specific functions instead of trying to handle the
corners inside btrfs_decompress_buf2page

Signed-off-by: Chris Mason <clm@fb.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Reported-by: Don A. Bailey <donb@securitymouse.com>
cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/fs/btrfs/lzo.c b/fs/btrfs/lzo.c
index 78285f30909e..617553cdb7d3 100644
--- a/fs/btrfs/lzo.c
+++ b/fs/btrfs/lzo.c
@@ -373,6 +373,8 @@ cont:
         }
 done:
         kunmap(pages_in[page_in_index]);
+        if (!ret)
+                btrfs_clear_biovec_end(bvec, vcnt, page_out_index, pg_offset);
         return ret;
 }
 
@@ -410,10 +412,23 @@ static int lzo_decompress(struct list_head *ws, unsigned char *data_in,
                 goto out;
         }
 
+        /*
+         * the caller is already checking against PAGE_SIZE, but lets
+         * move this check closer to the memcpy/memset
+         */
+        destlen = min_t(unsigned long, destlen, PAGE_SIZE);
         bytes = min_t(unsigned long, destlen, out_len - start_byte);
 
         kaddr = kmap_atomic(dest_page);
         memcpy(kaddr, workspace->buf + start_byte, bytes);
+
+        /*
+         * btrfs_getblock is doing a zero on the tail of the page too,
+         * but this will cover anything missing from the decompressed
+         * data.
+         */
+        if (bytes < destlen)
+                memset(kaddr+bytes, 0, destlen-bytes);
         kunmap_atomic(kaddr);
 out:
         return ret;