Re: [PATCH] fanotify: avoid possible NULL dereference

[Amir Goldstein]

On Tue, Aug 8, 2023 at 12:19 PM Su Hui <suhui@xxxxxxxxxxxx> wrote:
>
> smatch error:
> fs/notify/fanotify/fanotify_user.c:462 copy_fid_info_to_user():
> we previously assumed 'fh' could be null (see line 421)
>
> Fixes: afc894c784c8 ("fanotify: Store fanotify handles differently")
> Signed-off-by: Su Hui <suhui@xxxxxxxxxxxx>'

Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx>

> ---
>  fs/notify/fanotify/fanotify_user.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index f69c451018e3..5a5487ae2460 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -459,12 +459,13 @@ static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
>         if (WARN_ON_ONCE(len < sizeof(handle)))
>                 return -EFAULT;
>
> -       handle.handle_type = fh->type;
>         handle.handle_bytes = fh_len;
>
>         /* Mangle handle_type for bad file_handle */
>         if (!fh_len)
>                 handle.handle_type = FILEID_INVALID;
> +       else
> +               handle.handle_type = fh->type;
>
>         if (copy_to_user(buf, &handle, sizeof(handle)))
>                 return -EFAULT;
> --
> 2.30.2
>