Subject: [PATCH net-next] net/mlx5e: Fix use-after-free in mlx5e_stats_grp_sw_update_stats

From: Saeed Mahameed <[email-masked]>
Date: Fri, 11 Mar 2022 16:53:53 -0800

From: Saeed Mahameed <[email-masked]>

We need to sync page pool stats only for active channels. Reading ethtool
stats on a down netdev or a netdev with modified number of channels will
result in a user-after-free, trying to access page pools that are freed
already.

BUG: KASAN: use-after-free in mlx5e_stats_grp_sw_update_stats+0x465/0xf80
Read of size 8 at addr ffff888004835e40 by task ethtool/720

Fixes: cc10e84b2ec3 ("mlx5: add support for page_pool_get_stats")
Signed-off-by: Saeed Mahameed <[email-masked]>
Reported-by: Jakub Kicinski <[email-masked]>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_stats.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c b/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c
index 336e4d04c5f2..bdc870f9c2f3 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_stats.c
@@ -521,14 +521,15 @@ static MLX5E_DECLARE_STATS_GRP_OP_UPDATE_STATS(sw)
 
 	memset(s, 0, sizeof(*s));
 
+	for (i = 0; i < priv->channels.num; i++) /* for active channels only */
+		mlx5e_stats_update_stats_rq_page_pool(priv->channels.c[i]);
+
 	for (i = 0; i < priv->stats_nch; i++) {
 		struct mlx5e_channel_stats *channel_stats =
 			priv->channel_stats[i];
 
 		int j;
 
-		mlx5e_stats_update_stats_rq_page_pool(priv->channels.c[i]);
-
 		mlx5e_stats_grp_sw_update_stats_rq_stats(s, &channel_stats->rq);
 		mlx5e_stats_grp_sw_update_stats_xdpsq(s, &channel_stats->rq_xdpsq);
 		mlx5e_stats_grp_sw_update_stats_ch_stats(s, &channel_stats->ch);
-- 
2.35.1