This is a note to let you know that I've just added the patch titled
nilfs2: fix potential oob read in nilfs_btree_check_delete()
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nilfs2-fix-potential-oob-read-in-nilfs_btree_check_d.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit ff2fac05ea278f6e0a16adbb55567f562a06e61b
Author: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Date: Wed Sep 4 17:13:09 2024 +0900
nilfs2: fix potential oob read in nilfs_btree_check_delete()
[ Upstream commit f9c96351aa6718b42a9f42eaf7adce0356bdb5e8 ]
The function nilfs_btree_check_delete(), which checks whether degeneration
to direct mapping occurs before deleting a b-tree entry, causes memory
access outside the block buffer when retrieving the maximum key if the
root node has no entries.
This does not usually happen because b-tree mappings with 0 child nodes
are never created by mkfs.nilfs2 or nilfs2 itself. However, it can happen
if the b-tree root node read from a device is configured that way, so fix
this potential issue by adding a check for that case.
Link: https://lkml.kernel.org/r/20240904081401.16682-4-konishi.ryusuke@xxxxxxxxx
Fixes: 17c76b0104e4 ("nilfs2: B-tree based block mapping")
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx>
Cc: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/nilfs2/btree.c b/fs/nilfs2/btree.c
index 7cfff27b4b4a5..7c9f4d79bdbc5 100644
--- a/fs/nilfs2/btree.c
+++ b/fs/nilfs2/btree.c
@@ -1660,13 +1660,16 @@ static int nilfs_btree_check_delete(struct nilfs_bmap *btree, __u64 key)
int nchildren, ret;
root = nilfs_btree_get_root(btree);
+ nchildren = nilfs_btree_node_get_nchildren(root);
+ if (unlikely(nchildren == 0))
+ return 0;
+
switch (nilfs_btree_height(btree)) {
case 2:
bh = NULL;
node = root;
break;
case 3:
- nchildren = nilfs_btree_node_get_nchildren(root);
if (nchildren > 1)
return 0;
ptr = nilfs_btree_node_get_ptr(root, nchildren - 1,
@@ -1675,12 +1678,12 @@ static int nilfs_btree_check_delete(struct nilfs_bmap *btree, __u64 key)
if (ret < 0)
return ret;
node = (struct nilfs_btree_node *)bh->b_data;
+ nchildren = nilfs_btree_node_get_nchildren(node);
break;
default:
return 0;
}
- nchildren = nilfs_btree_node_get_nchildren(node);
maxkey = nilfs_btree_node_get_key(node, nchildren - 1);
nextmaxkey = (nchildren > 1) ?
nilfs_btree_node_get_key(node, nchildren - 2) : 0;
