Messages in this thread Patch in this message |  | | From | Paul Gortmaker <> | Subject | [v2.6.34-stable 54/77] hfs: fix hfs_find_init() sb->ext_tree NULL ptr oops | Date | Tue, 8 Jan 2013 18:35:33 -0500 |
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From: Phillip Lougher <plougher@redhat.com>
------------------- This is a commit scheduled for the next v2.6.34 longterm release. http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git If you see a problem with using this for longterm, please comment. -------------------
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 >= 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 <clement.lecigne@netasq.com> Signed-off-by: Phillip Lougher <plougher@redhat.com> Cc: Jeff Mahoney <jeffm@suse.com> Cc: Christoph Hellwig <hch@lst.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> --- fs/hfs/btree.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/fs/hfs/btree.c b/fs/hfs/btree.c index 38a0a99..d4e98a7 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)) -- 1.7.12.1
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