Re: [Intel-wired-lan] [PATCH][V3] e1000: avoid null pointer dereference on invalid stat type

From: Alexander Duyck
Date: Fri Sep 22 2017 - 14:09:25 EST


On Fri, Sep 22, 2017 at 10:13 AM, Colin King <colin.king@xxxxxxxxxxxxx> wrote:
> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>
> Currently if the stat type is invalid then data[i] is being set
> either by dereferencing a null pointer p, or it is reading from
> an incorrect previous location if we had a valid stat type
> previously. Fix this by skipping over the read of p on an invalid
> stat type.
>
> Detected by CoverityScan, CID#113385 ("Explicit null dereferenced")
>
> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>

Looks good to me.

Reviewed-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxx>

> ---
> drivers/net/ethernet/intel/e1000/e1000_ethtool.c | 9 ++++-----
> 1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/e1000/e1000_ethtool.c b/drivers/net/ethernet/intel/e1000/e1000_ethtool.c
> index ec8aa4562cc9..3b3983a1ffbb 100644
> --- a/drivers/net/ethernet/intel/e1000/e1000_ethtool.c
> +++ b/drivers/net/ethernet/intel/e1000/e1000_ethtool.c
> @@ -1824,11 +1824,12 @@ static void e1000_get_ethtool_stats(struct net_device *netdev,
> {
> struct e1000_adapter *adapter = netdev_priv(netdev);
> int i;
> - char *p = NULL;
> const struct e1000_stats *stat = e1000_gstrings_stats;
>
> e1000_update_stats(adapter);
> - for (i = 0; i < E1000_GLOBAL_STATS_LEN; i++) {
> + for (i = 0; i < E1000_GLOBAL_STATS_LEN; i++, stat++) {
> + char *p;
> +
> switch (stat->type) {
> case NETDEV_STATS:
> p = (char *)netdev + stat->stat_offset;
> @@ -1839,15 +1840,13 @@ static void e1000_get_ethtool_stats(struct net_device *netdev,
> default:
> WARN_ONCE(1, "Invalid E1000 stat type: %u index %d\n",
> stat->type, i);
> - break;
> + continue;
> }
>
> if (stat->sizeof_stat == sizeof(u64))
> data[i] = *(u64 *)p;
> else
> data[i] = *(u32 *)p;
> -
> - stat++;
> }
> /* BUG_ON(i != E1000_STATS_LEN); */
> }
> --
> 2.14.1
>
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