On Sat, 2018-11-24 at 10:10 +0800, Pan Bian wrote:
> The function hfs_bmap_free frees node via hfs_bnode_put(node).
> However,
> it then reads node->this when dumping error message on an error path,
> which may result in a use-after-free bug. This patch frees node only
> when it is never used.
>
> Fixes: a1185ffa2fc("HFS rewrite")
>
> Signed-off-by: Pan Bian <[email protected]>
>
> ---
> V2: correct the commit information in Fixes
By the way, HFS+ has the same issue [1].
>
> ---
> fs/hfs/btree.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/hfs/btree.c b/fs/hfs/btree.c
> index 98b96ff..19017d2 100644
> --- a/fs/hfs/btree.c
> +++ b/fs/hfs/btree.c
> @@ -338,13 +338,14 @@ void hfs_bmap_free(struct hfs_bnode *node)
>
> nidx -= len * 8;
> i = node->next;
> - hfs_bnode_put(node);
> if (!i) {
> /* panic */;
> pr_crit("unable to free bnode %u. bmap not
> found!\n",
> node->this);
> + hfs_bnode_put(node);
> return;
> }
> + hfs_bnode_put(node);
First of all, it looks weird to have two calls of hfs_bnode_put(node).
Secondly, you will add only one line of code instead of two if you
simply save the node->this in the local variable.
> node = hfs_bnode_find(tree, i);
> if (IS_ERR(node))
> return;
Thanks,
Vyacheslav Dubeyko.
[1] https://elixir.bootlin.com/linux/latest/source/fs/hfsplus/btree.c#L457
