[PATCH net] net/mlx5e: Fix queue stats access to queues without stats

[Breno Leitao <leitao@debian.org>]

I am seeing the following mlx5e crash in the Meta fleet:

  pc : mlx5e_get_queue_stats_rx+0x4c/0xc8
  Call trace:
   mlx5e_get_queue_stats_rx+0x4c/0xc8 (P)
   netdev_stat_queue_sum+0x78/0x480
   netdev_nl_qstats_get_dump_one+0xf0/0x268
   netdev_nl_qstats_get_dumpit+0x7c/0x1f8

When dumping device-wide qstats, the core calls the per-queue callbacks
for every queue below real_num_{rx,tx}_queues, regardless of whether the
netdev is up. Some of those queues have no stats behind them:

 - RX stats live in priv->channel_stats[], which only has entries for
   channels that have been opened (stats_nch). real_num_rx_queues can
   be larger, for example after the channel count is raised while the
   netdev is down, or after opening the channels failed part way.

 - TX stats are looked up in priv->txq2sq_stats[], which is NULL for
   SQs that were never activated and for HTB queues while the channels
   are closed.

In both cases the callback dereferences a NULL pointer. The dump needs
no privileges, so any user can trigger it.

Return early for RX queues at or above stats_nch and for TX queues
without SQ stats.

Fixes: 7b66ae536a78 ("net/mlx5e: Add per queue netdev-genl stats")
Cc: stable@vger.kernel.org
Signed-off-by: Breno Leitao <leitao@debian.org>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index c3c2c5720c6f32..72bca10c579df9 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -5489,7 +5489,7 @@ static void mlx5e_get_queue_stats_rx(struct net_device *dev, int i,
 	struct mlx5e_rq_stats *xskrq_stats;
 	struct mlx5e_rq_stats *rq_stats;
 
-	if (mlx5e_is_uplink_rep(priv) || !mlx5e_stats_nch_read(priv))
+	if (mlx5e_is_uplink_rep(priv) || i >= mlx5e_stats_nch_read(priv))
 		return;
 
 	channel_stats = priv->channel_stats[i];
@@ -5521,6 +5521,9 @@ static void mlx5e_get_queue_stats_tx(struct net_device *dev, int i,
 	 * inactive sqs.
 	 */
 	sq_stats = priv->txq2sq_stats[i];
+	if (!sq_stats)
+		return;
+
 	stats->packets = sq_stats->packets;
 	stats->bytes = sq_stats->bytes;
 

---
base-commit: 241dec6f9ab74d8c3ef246764f3611666b96b9e1
change-id: 20261104-mlx5e-qstats-null-39d642e7eef7

Best regards,
--  
Breno Leitao <leitao@debian.org>