Squashfs: Fix oops when reading fsfuzzer corrupted filesystems

This fixes a code regression caused by the recent mainlining changes.
The recent code changes call zlib_inflate repeatedly, decompressing into
separate 4K buffers, this code didn't check for the possibility that
zlib_inflate might ask for too many buffers when decompressing corrupted
data.

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>

fs/squashfs/block.c

@@ -80,7 +80,7 @@ static struct buffer_head *get_block_length(struct super_block *sb,
  * generated a larger block - this does occasionally happen with zlib).
  */
 int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
-			int length, u64 *next_index, int srclength)
+			int length, u64 *next_index, int srclength, int pages)
 {
 	struct squashfs_sb_info *msblk = sb->s_fs_info;
 	struct buffer_head **bh;
@@ -185,6 +185,14 @@ int squashfs_read_data(struct super_block *sb, void **buffer, u64 index,
 			}
 
 			if (msblk->stream.avail_out == 0) {
+				if (page == pages) {
+					ERROR("zlib_inflate tried to "
+						"decompress too much data, "
+						"expected %d bytes.  Zlib "
+						"data probably corrupt\n",
+						srclength);
+					goto release_mutex;
+				}
 				msblk->stream.next_out = buffer[page++];
 				msblk->stream.avail_out = PAGE_CACHE_SIZE;
 			}
@@ -268,7 +276,8 @@ block_release:
 		put_bh(bh[k]);
 
 read_failure:
-	ERROR("sb_bread failed reading block 0x%llx\n", cur_index);
+	ERROR("squashfs_read_data failed to read block 0x%llx\n",
+					(unsigned long long) index);
 	kfree(bh);
 	return -EIO;
 }

fs/squashfs/cache.c

@@ -119,7 +119,7 @@ struct squashfs_cache_entry *squashfs_cache_get(struct super_block *sb,
 
 			entry->length = squashfs_read_data(sb, entry->data,
 				block, length, &entry->next_index,
-				cache->block_size);
+				cache->block_size, cache->pages);
 
 			spin_lock(&cache->lock);
 
@@ -406,7 +406,7 @@ int squashfs_read_table(struct super_block *sb, void *buffer, u64 block,
 	for (i = 0; i < pages; i++, buffer += PAGE_CACHE_SIZE)
 		data[i] = buffer;
 	res = squashfs_read_data(sb, data, block, length |
-		SQUASHFS_COMPRESSED_BIT_BLOCK, NULL, length);
+		SQUASHFS_COMPRESSED_BIT_BLOCK, NULL, length, pages);
 	kfree(data);
 	return res;
 }

fs/squashfs/squashfs.h

@@ -34,7 +34,7 @@ static inline struct squashfs_inode_info *squashfs_i(struct inode *inode)
 
 /* block.c */
 extern int squashfs_read_data(struct super_block *, void **, u64, int, u64 *,
-				int);
+				int, int);
 
 /* cache.c */
 extern struct squashfs_cache *squashfs_cache_init(char *, int, int);

fs/squashfs/super.c

@@ -389,7 +389,7 @@ static int __init init_squashfs_fs(void)
 		return err;
 	}
 
-	printk(KERN_INFO "squashfs: version 4.0 (2009/01/03) "
+	printk(KERN_INFO "squashfs: version 4.0 (2009/01/31) "
 		"Phillip Lougher\n");
 
 	return 0;