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    Subject[36/53] hfs: fix hfs_find_init() sb->ext_tree NULL ptr oops
    3.1-stable review patch.  If anyone has any objections, please let me know.


    From: Phillip Lougher <>

    commit 434a964daa14b9db083ce20404a4a2add54d037a upstream.

    Clement Lecigne reports a filesystem which causes a kernel oops in
    hfs_find_init() trying to dereference sb->ext_tree which is NULL.

    This proves to be because the filesystem has a corrupted MDB extent
    record, where the extents file does not fit into the first three extents
    in the file record (the first blocks).

    In hfs_get_block() when looking up the blocks for the extent file
    (HFS_EXT_CNID), it fails the first blocks special case, and falls
    through to the extent code (which ultimately calls hfs_find_init())
    which is in the process of being initialised.

    Hfs avoids this scenario by always having the extents b-tree fitting
    into the first blocks (the extents B-tree can't have overflow extents).

    The fix is to check at mount time that the B-tree fits into first
    blocks, i.e. fail if HFS_I(inode)->alloc_blocks >=

    Note, the existing commit 47f365eb57573 ("hfs: fix oops on mount with
    corrupted btree extent records") becomes subsumed into this as a special
    case, but only for the extents B-tree (HFS_EXT_CNID), it is perfectly
    acceptable for the catalog B-Tree file to grow beyond three extents,
    with the remaining extent descriptors in the extents overfow.

    This fixes CVE-2011-2203

    Reported-by: Clement LECIGNE <>
    Signed-off-by: Phillip Lougher <>
    Cc: Jeff Mahoney <>
    Cc: Christoph Hellwig <>
    Signed-off-by: Andrew Morton <>
    Signed-off-by: Linus Torvalds <>
    Cc: Moritz Mühlenhoff <>
    Signed-off-by: Greg Kroah-Hartman <>

    fs/hfs/btree.c | 20 +++++++++++++++-----
    1 file changed, 15 insertions(+), 5 deletions(-)

    --- a/fs/hfs/btree.c
    +++ b/fs/hfs/btree.c
    @@ -46,11 +46,26 @@ struct hfs_btree *hfs_btree_open(struct
    case HFS_EXT_CNID:
    hfs_inode_read_fork(tree->inode, mdb->drXTExtRec, mdb->drXTFlSize,
    mdb->drXTFlSize, be32_to_cpu(mdb->drXTClpSiz));
    + if (HFS_I(tree->inode)->alloc_blocks >
    + HFS_I(tree->inode)->first_blocks) {
    + printk(KERN_ERR "hfs: invalid btree extent records\n");
    + unlock_new_inode(tree->inode);
    + goto free_inode;
    + }
    tree->inode->i_mapping->a_ops = &hfs_btree_aops;
    case HFS_CAT_CNID:
    hfs_inode_read_fork(tree->inode, mdb->drCTExtRec, mdb->drCTFlSize,
    mdb->drCTFlSize, be32_to_cpu(mdb->drCTClpSiz));
    + if (!HFS_I(tree->inode)->first_blocks) {
    + printk(KERN_ERR "hfs: invalid btree extent records "
    + "(0 size).\n");
    + unlock_new_inode(tree->inode);
    + goto free_inode;
    + }
    tree->inode->i_mapping->a_ops = &hfs_btree_aops;
    @@ -59,11 +74,6 @@ struct hfs_btree *hfs_btree_open(struct

    - if (!HFS_I(tree->inode)->first_blocks) {
    - printk(KERN_ERR "hfs: invalid btree extent records (0 size).\n");
    - goto free_inode;
    - }
    mapping = tree->inode->i_mapping;
    page = read_mapping_page(mapping, 0, NULL);
    if (IS_ERR(page))

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      Last update: 2011-12-16 21:07    [W:0.024 / U:3.168 seconds]
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