[PATCH 61/91] hfs: fix hfs_find_init() sb->ext_tree NULL ptr oops

From: Willy Tarreau
Date: Sun Feb 05 2012 - 17:31:46 EST


2.6.27-longterm review patch. If anyone has any objections, please let us know.

------------------

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.

[WT: patch edited - 47f365eb57573 was missing from 2.6.27.x]

This fixes CVE-2011-2203

Reported-by: Clement LECIGNE <clement.lecigne@xxxxxxxxxx>
Signed-off-by: Phillip Lougher <plougher@xxxxxxxxxx>
Cc: Jeff Mahoney <jeffm@xxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Moritz Mühlenhoff <jmm@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
fs/hfs/btree.c | 20 +++++++++++++++-----
1 files changed, 15 insertions(+), 5 deletions(-)

Index: longterm-2.6.27/fs/hfs/btree.c
===================================================================
--- longterm-2.6.27.orig/fs/hfs/btree.c 2012-02-05 22:34:33.129915287 +0100
+++ longterm-2.6.27/fs/hfs/btree.c 2012-02-05 22:34:43.555914905 +0100
@@ -45,11 +45,26 @@
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:


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/