mkfs.btrfs: write zeroes instead on uninitialized data.

Found by valgrind:
==8968== Use of uninitialised value of size 8
==8968==    at 0x41CE7D: crc32c_le (crc32c.c:98)
==8968==    by 0x40A1D0: csum_tree_block_size (disk-io.c:82)
==8968==    by 0x40A2D4: csum_tree_block (disk-io.c:105)
==8968==    by 0x40A7D6: write_tree_block (disk-io.c:241)
==8968==    by 0x40ACEE: __commit_transaction (disk-io.c:354)
==8968==    by 0x40AE9E: btrfs_commit_transaction (disk-io.c:385)
==8968==    by 0x42CF66: make_image (mkfs.c:1061)
==8968==    by 0x42DE63: main (mkfs.c:1410)
==8968==  Uninitialised value was created by a stack allocation
==8968==    at 0x42B5FB: add_inode_items (mkfs.c:493)

1. On-disk inode format has reserved (and thus, random at alloc time) fields:
   btrfs_inode_item: __le64 reserved[4]
2. Sometimes extents are created on disk without writing data there.
   (Or at least not all data is written there). Kernel code always had
   it kzalloc'ed.
Zero them all.

Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Signed-off-by: Hugo Mills <hugo@carfax.org.uk>

diff --git a/extent_io.c b/extent_io.c
index 70fecbb..8f0a876 100644 (file)
--- a/extent_io.c
+++ b/extent_io.c
@@ -568,6 +568,7 @@ static struct extent_buffer *__alloc_extent_buffer(struct extent_io_tree *tree,
                BUG();
                return NULL;
        }
+       memset(eb, 0, sizeof(struct extent_buffer) + blocksize);
 
        eb->start = bytenr;
        eb->len = blocksize;

diff --git a/mkfs.c b/mkfs.c
index 5e483dc..428ec18 100644 (file)
--- a/mkfs.c
+++ b/mkfs.c
@@ -411,6 +411,13 @@ static int fill_inode_item(struct btrfs_trans_handle *trans,
        u64 blocks = 0;
        u64 sectorsize = root->sectorsize;
 
+       /*
+        * btrfs_inode_item has some reserved fields
+        * and represents on-disk inode entry, so
+        * zero everything to prevent information leak
+        */
+       memset(dst, 0, sizeof (*dst));
+
        btrfs_set_stack_inode_generation(dst, trans->transid);
        btrfs_set_stack_inode_size(dst, src->st_size);
        btrfs_set_stack_inode_nbytes(dst, 0);