Re: [PATCH] ocfs2: Fix a use after free on error

Joseph Qi
2021-02-02T01:49:17Z

On 2/1/21 8:25 PM, Dan Carpenter wrote:
> The error handling in this function frees "reg" but it is still on the
> "o2hb_all_regions" list so it will lead to a use after free. The fix
> for this is to only add it to the list after everything has succeeded.
>
Seems we have to clear the bitmap as well in error case.
So how about add a new error label and handle them both?

Thanks,
Joseph

> Fixes: 1cf257f51191 ("ocfs2: fix memory leak")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> This is from static analysis and hasn't been tested.
>
> fs/ocfs2/cluster/heartbeat.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ocfs2/cluster/heartbeat.c b/fs/ocfs2/cluster/heartbeat.c
> index 0179a73a3fa2..92af4dc813e7 100644
> --- a/fs/ocfs2/cluster/heartbeat.c
> +++ b/fs/ocfs2/cluster/heartbeat.c
> @@ -2025,7 +2025,6 @@ static struct config_item *o2hb_heartbeat_group_make_item(struct config_group *g
> }
> set_bit(reg->hr_region_num, o2hb_region_bitmap);
> }
> - list_add_tail(&reg->hr_all_item, &o2hb_all_regions);
> spin_unlock(&o2hb_live_lock);
>
> config_item_init_type_name(&reg->hr_item, name, &o2hb_region_type);
> @@ -2053,6 +2052,10 @@ static struct config_item *o2hb_heartbeat_group_make_item(struct config_group *g
>
> o2hb_debug_region_init(reg, o2hb_debug_dir);
>
> + spin_lock(&o2hb_live_lock);
> + list_add_tail(&reg->hr_all_item, &o2hb_all_regions);
> + spin_unlock(&o2hb_live_lock);
> +
> return &reg->hr_item;
>
> unregister_handler:
>