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>

4 files changed, 67 insertions, 5 deletions

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index d3220d31d3cb..dcd9be32ac57 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -1011,8 +1011,6 @@ int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
                 bytes = min(bytes, working_bytes);
                 kaddr = kmap_atomic(page_out);
                 memcpy(kaddr + *pg_offset, buf + buf_offset, bytes);
-                if (*pg_index == (vcnt - 1) && *pg_offset == 0)
-                        memset(kaddr + bytes, 0, PAGE_CACHE_SIZE - bytes);
                 kunmap_atomic(kaddr);
                 flush_dcache_page(page_out);
 
@@ -1054,3 +1052,34 @@ int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
 
         return 1;
 }
+
+/*
+ * When uncompressing data, we need to make sure and zero any parts of
+ * the biovec that were not filled in by the decompression code.  pg_index
+ * and pg_offset indicate the last page and the last offset of that page
+ * that have been filled in.  This will zero everything remaining in the
+ * biovec.
+ */
+void btrfs_clear_biovec_end(struct bio_vec *bvec, int vcnt,
+                                   unsigned long pg_index,
+                                   unsigned long pg_offset)
+{
+        while (pg_index < vcnt) {
+                struct page *page = bvec[pg_index].bv_page;
+                unsigned long off = bvec[pg_index].bv_offset;
+                unsigned long len = bvec[pg_index].bv_len;
+
+                if (pg_offset < off)
+                        pg_offset = off;
+                if (pg_offset < off + len) {
+                        unsigned long bytes = off + len - pg_offset;
+                        char *kaddr;
+
+                        kaddr = kmap_atomic(page);
+                        memset(kaddr + pg_offset, 0, bytes);
+                        kunmap_atomic(kaddr);
+                }
+                pg_index++;
+                pg_offset = 0;
+        }
+}
diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
index 0c803b4fbf93..d181f70caae0 100644
--- a/fs/btrfs/compression.h
+++ b/fs/btrfs/compression.h
@@ -45,7 +45,9 @@ int btrfs_submit_compressed_write(struct inode *inode, u64 start,
                                   unsigned long nr_pages);
 int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
                                  int mirror_num, unsigned long bio_flags);
-
+void btrfs_clear_biovec_end(struct bio_vec *bvec, int vcnt,
+                                   unsigned long pg_index,
+                                   unsigned long pg_offset);
 struct btrfs_compress_op {
         struct list_head *(*alloc_workspace)(void);
 
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;
diff --git a/fs/btrfs/zlib.c b/fs/btrfs/zlib.c
index 759fa4e2de8f..fb22fd8d8fb8 100644
--- a/fs/btrfs/zlib.c
+++ b/fs/btrfs/zlib.c
@@ -299,6 +299,8 @@ done:
         zlib_inflateEnd(&workspace->strm);
         if (data_in)
                 kunmap(pages_in[page_in_index]);
+        if (!ret)
+                btrfs_clear_biovec_end(bvec, vcnt, page_out_index, pg_offset);
         return ret;
 }
 
@@ -310,10 +312,14 @@ static int zlib_decompress(struct list_head *ws, unsigned char *data_in,
         struct workspace *workspace = list_entry(ws, struct workspace, list);
         int ret = 0;
         int wbits = MAX_WBITS;
-        unsigned long bytes_left = destlen;
+        unsigned long bytes_left;
         unsigned long total_out = 0;
+        unsigned long pg_offset = 0;
         char *kaddr;
 
+        destlen = min_t(unsigned long, destlen, PAGE_SIZE);
+        bytes_left = destlen;
+
         workspace->strm.next_in = data_in;
         workspace->strm.avail_in = srclen;
         workspace->strm.total_in = 0;
@@ -341,7 +347,6 @@ static int zlib_decompress(struct list_head *ws, unsigned char *data_in,
                 unsigned long buf_start;
                 unsigned long buf_offset;
                 unsigned long bytes;
-                unsigned long pg_offset = 0;
 
                 ret = zlib_inflate(&workspace->strm, Z_NO_FLUSH);
                 if (ret != Z_OK && ret != Z_STREAM_END)
@@ -384,6 +389,17 @@ next:
                 ret = 0;
 
         zlib_inflateEnd(&workspace->strm);
+
+        /*
+         * this should only happen if zlib returned fewer bytes than we
+         * expected.  btrfs_get_block is responsible for zeroing from the
+         * end of the inline extent (destlen) to the end of the page
+         */
+        if (pg_offset < destlen) {
+                kaddr = kmap_atomic(dest_page);
+                memset(kaddr + pg_offset, 0, destlen - pg_offset);
+                kunmap_atomic(kaddr);
+        }
         return ret;
 }