Re: [Linux-kernel-mentees] [PATCH net] xdp: Prevent kernel-infoleak in xsk_getsockopt()

[Song Liu]

On Mon, Jul 27, 2020 at 7:30 PM Peilin Ye <yepeilin.cs@xxxxxxxxx> wrote:
>
> xsk_getsockopt() is copying uninitialized stack memory to userspace when
> `extra_stats` is `false`. Fix it by initializing `stats` with memset().
>
> Cc: stable@xxxxxxxxxxxxxxx

8aa5a33578e9 is not in stable branches yet, so we don't need to Cc stable.

> Fixes: 8aa5a33578e9 ("xsk: Add new statistics")
> Suggested-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Signed-off-by: Peilin Ye <yepeilin.cs@xxxxxxxxx>
> ---
>  net/xdp/xsk.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 26e3bba8c204..acf001908a0d 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -844,6 +844,8 @@ static int xsk_getsockopt(struct socket *sock, int level, int optname,
>                 bool extra_stats = true;
>                 size_t stats_size;
>
> +               memset(&stats, 0, sizeof(stats));
> +

xsk.c doesn't include linux/string.h directly, so using memset may break
build for some config combinations. We can probably just use

struct xdp_statistics stats = {};

Thanks,
Song


>                 if (len < sizeof(struct xdp_statistics_v1)) {
>                         return -EINVAL;
>                 } else if (len < sizeof(stats)) {
> --
> 2.25.1
>