From 434a964daa14b9db083ce20404a4a2add54d037a Mon Sep 17 00:00:00 2001 From: Phillip Lougher Date: Wed, 2 Nov 2011 13:38:01 -0700 Subject: hfs: fix hfs_find_init() sb->ext_tree NULL ptr oops 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 >= HFS_I(inode)->first_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 --- fs/hfs/btree.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) (limited to 'fs/hfs/btree.c') diff --git a/fs/hfs/btree.c b/fs/hfs/btree.c index 3ebc437736fe..1cbdeea1db44 100644 --- a/fs/hfs/btree.c +++ b/fs/hfs/btree.c @@ -46,11 +46,26 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id, btree_keycmp ke 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; break; 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; break; default: @@ -59,11 +74,6 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id, btree_keycmp ke } unlock_new_inode(tree->inode); - 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)) -- cgit v1.2.2