[PATCH net v2] net/mlx5e: Fix use-after-free in mlx5e_tx_reporter_timeout_recover

[Matt Fleming <matt@readmodwrite.com>]

From: Matt Fleming <mfleming@cloudflare.com>

mlx5e_tx_reporter_timeout_recover() accesses sq->netdev after
mlx5e_safe_reopen_channels() has torn down and freed the channel (and
its embedded SQs). Replace the three sq->netdev references with
priv->netdev which is safe because priv outlives channel teardown.

The netdev_err() call already used priv->netdev for this reason; make
the trylock/unlock and health_channel_eq_recover calls consistent.

This fixes the following KASAN splat:

  BUG: KASAN: use-after-free in mlx5e_tx_reporter_timeout_recover+0x1dd/0x360 [mlx5_core]
  Read of size 8 at addr ffff889860ed0b28 by task kworker/u113:2/5277

  Call Trace:
   mlx5e_tx_reporter_timeout_recover+0x1dd/0x360 [mlx5_core]
   devlink_health_reporter_recover+0xa2/0x150
   devlink_health_report+0x254/0x7c0
   mlx5e_reporter_tx_timeout+0x297/0x380 [mlx5_core]
   mlx5e_tx_timeout_work+0x109/0x170 [mlx5_core]
   process_one_work+0x677/0xf20
   worker_thread+0x51f/0xd90
   kthread+0x3a5/0x810
   ret_from_fork+0x208/0x400
   ret_from_fork_asm+0x1a/0x30

Fixes: 83ac0304a2d7 ("net/mlx5e: Fix deadlocks between devlink and netdev instance locks")
Cc: stable@vger.kernel.org
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Matt Fleming <mfleming@cloudflare.com>
---
Changes in v2:
  - Add Cc: stable and Reviewed-by tags from Cosmin and Tariq.
  - Add people from the Fixes: commit and related discussion to Cc.
---

 drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c
index afdeb1b3d425..8409ae73768f 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c
@@ -160,13 +160,13 @@ static int mlx5e_tx_reporter_timeout_recover(void *ctx)
 	 * channels are being closed for other reason and this work is not
 	 * relevant anymore.
 	 */
-	while (!netdev_trylock(sq->netdev)) {
+	while (!netdev_trylock(priv->netdev)) {
 		if (!test_bit(MLX5E_STATE_CHANNELS_ACTIVE, &priv->state))
 			return 0;
 		msleep(20);
 	}
 
-	err = mlx5e_health_channel_eq_recover(sq->netdev, eq, sq->cq.ch_stats);
+	err = mlx5e_health_channel_eq_recover(priv->netdev, eq, sq->cq.ch_stats);
 	if (!err) {
 		to_ctx->status = 0; /* this sq recovered */
 		goto out;
@@ -186,7 +186,7 @@ static int mlx5e_tx_reporter_timeout_recover(void *ctx)
 		   "mlx5e_safe_reopen_channels failed recovering from a tx_timeout, err(%d).\n",
 		   err);
 out:
-	netdev_unlock(sq->netdev);
+	netdev_unlock(priv->netdev);
 	return err;
 }
 
-- 
2.43.0