[patch added to the 3.12 stable tree] nilfs2: fix sanity check of btree level in nilfs_btree_root_broken()

Jiri Slaby
2015-05-15T14:28:32Z

From: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

This patch has been added to the 3.12 stable tree. If you have any
objections, please let us know.

===============

commit d8fd150fe3935e1692bf57c66691e17409ebb9c1 upstream.

The range check for b-tree level parameter in nilfs_btree_root_broken()
is wrong; it accepts the case of "level == NILFS_BTREE_LEVEL_MAX" even
though the level is limited to values in the range of 0 to
(NILFS_BTREE_LEVEL_MAX - 1).

Since the level parameter is read from storage device and used to index
nilfs_btree_path array whose element count is NILFS_BTREE_LEVEL_MAX, it
can cause memory overrun during btree operations if the boundary value
is set to the level parameter on device.

This fixes the broken sanity check and adds a comment to clarify that
the upper bound NILFS_BTREE_LEVEL_MAX is exclusive.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
fs/nilfs2/btree.c | 2 +-
include/linux/nilfs2_fs.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
index ecdbae19a766..090d8ce25bd1 100644
--- a/fs/nilfs2/btree.c
+++ b/fs/nilfs2/btree.c
@@ -388,7 +388,7 @@ static int nilfs_btree_root_broken(const struct nilfs_btree_node *node,
nchildren = nilfs_btree_node_get_nchildren(node);

if (unlikely(level < NILFS_BTREE_LEVEL_NODE_MIN ||
- level > NILFS_BTREE_LEVEL_MAX ||
+ level >= NILFS_BTREE_LEVEL_MAX ||
nchildren < 0 ||
nchildren > NILFS_BTREE_ROOT_NCHILDREN_MAX)) {
pr_crit("NILFS: bad btree root (inode number=%lu): level = %d, flags = 0x%x, nchildren = %d\n",
diff --git a/include/linux/nilfs2_fs.h b/include/linux/nilfs2_fs.h
index 98755767c7b0..1108acaacfc6 100644
--- a/include/linux/nilfs2_fs.h
+++ b/include/linux/nilfs2_fs.h
@@ -458,7 +458,7 @@ struct nilfs_btree_node {
/* level */
#define NILFS_BTREE_LEVEL_DATA 0
#define NILFS_BTREE_LEVEL_NODE_MIN (NILFS_BTREE_LEVEL_DATA + 1)
-#define NILFS_BTREE_LEVEL_MAX 14
+#define NILFS_BTREE_LEVEL_MAX 14 /* Max level (exclusive) */

/**
* struct nilfs_palloc_group_desc - block group descriptor
--
2.3.7