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 <[email protected]>
Cc: <[email protected]>
---
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 059f371..919fd5b 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 ff3fea3..9abb763 100644
--- a/include/linux/nilfs2_fs.h
+++ b/include/linux/nilfs2_fs.h
@@ -460,7 +460,7 @@ 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
--
1.8.3.1