This is a note to let you know that I've just added the patch titled
hfs: add lock nesting notation to hfs_find_init
to the 4.4-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:
hfs-add-lock-nesting-notation-to-hfs_find_init.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 64df80efde1899ae352ce31160e5b219065e9835
Author: Desmond Cheong Zhi Xi <desmondcheongzx@xxxxxxxxx>
Date: Wed Jul 14 21:27:08 2021 -0700
hfs: add lock nesting notation to hfs_find_init
[ Upstream commit b3b2177a2d795e35dc11597b2609eb1e7e57e570 ]
Syzbot reports a possible recursive lock in [1].
This happens due to missing lock nesting information. From the logs, we
see that a call to hfs_fill_super is made to mount the hfs filesystem.
While searching for the root inode, the lock on the catalog btree is
grabbed. Then, when the parent of the root isn't found, a call to
__hfs_bnode_create is made to create the parent of the root. This
eventually leads to a call to hfs_ext_read_extent which grabs a lock on
the extents btree.
Since the order of locking is catalog btree -> extents btree, this lock
hierarchy does not lead to a deadlock.
To tell lockdep that this locking is safe, we add nesting notation to
distinguish between catalog btrees, extents btrees, and attributes
btrees (for HFS+). This has already been done in hfsplus.
Link: https://syzkaller.appspot.com/bug?id=f007ef1d7a31a469e3be7aeb0fde0769b18585db [1]
Link: https://lkml.kernel.org/r/20210701030756.58760-4-desmondcheongzx@xxxxxxxxx
Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@xxxxxxxxx>
Reported-by: syzbot+b718ec84a87b7e73ade4@xxxxxxxxxxxxxxxxxxxxxxxxx
Tested-by: syzbot+b718ec84a87b7e73ade4@xxxxxxxxxxxxxxxxxxxxxxxxx
Reviewed-by: Viacheslav Dubeyko <slava@xxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx>
Cc: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/hfs/bfind.c b/fs/hfs/bfind.c
index de69d8a24f6d..7f2ef95dcd05 100644
--- a/fs/hfs/bfind.c
+++ b/fs/hfs/bfind.c
@@ -24,7 +24,19 @@ int hfs_find_init(struct hfs_btree *tree, struct hfs_find_data *fd)
fd->key = ptr + tree->max_key_len + 2;
hfs_dbg(BNODE_REFS, "find_init: %d (%p)\n",
tree->cnid, __builtin_return_address(0));
- mutex_lock(&tree->tree_lock);
+ switch (tree->cnid) {
+ case HFS_CAT_CNID:
+ mutex_lock_nested(&tree->tree_lock, CATALOG_BTREE_MUTEX);
+ break;
+ case HFS_EXT_CNID:
+ mutex_lock_nested(&tree->tree_lock, EXTENTS_BTREE_MUTEX);
+ break;
+ case HFS_ATTR_CNID:
+ mutex_lock_nested(&tree->tree_lock, ATTR_BTREE_MUTEX);
+ break;
+ default:
+ return -EINVAL;
+ }
return 0;
}
diff --git a/fs/hfs/btree.h b/fs/hfs/btree.h
index 2715f416b5a8..308b5f1af65b 100644
--- a/fs/hfs/btree.h
+++ b/fs/hfs/btree.h
@@ -12,6 +12,13 @@ typedef int (*btree_keycmp)(const btree_key *, const btree_key *);
#define NODE_HASH_SIZE 256
+/* B-tree mutex nested subclasses */
+enum hfs_btree_mutex_classes {
+ CATALOG_BTREE_MUTEX,
+ EXTENTS_BTREE_MUTEX,
+ ATTR_BTREE_MUTEX,
+};
+
/* A HFS BTree held in memory */
struct hfs_btree {
struct super_block *sb;
