net/mlx5: Fix command entry leak in Internal Error State

stable inclusion
from linux-4.19.123
commit 7ddb6aa96a57a4724b590b82ac6cebc0f08b78b6

--------------------------------

[ Upstream commit cece6f43 ]

Processing commands by cmd_work_handler() while already in Internal
Error State will result in entry leak, since the handler process force
completion without doorbell. Forced completion doesn't release the entry
and event completion will never arrive, so entry should be released.

Fixes: 73dd3a48 ("net/mlx5: Avoid using pending command interface slots")
Signed-off-by: NMoshe Shemesh <moshe@mellanox.com>
Signed-off-by: NEran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: NSaeed Mahameed <saeedm@mellanox.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Signed-off-by: NLi Aichun <liaichun@huawei.com>
Reviewed-by: Nguodeqing <geffrey.guo@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/net/ethernet/mellanox/mlx5/core/cmd.c

@@ -896,6 +896,10 @@ static void cmd_work_handler(struct work_struct *work)
 		MLX5_SET(mbox_out, ent->out, syndrome, drv_synd);
 
 		mlx5_cmd_comp_handler(dev, 1UL << ent->idx, true);
+		/* no doorbell, no need to keep the entry */
+		free_ent(cmd, ent->idx);
+		if (ent->callback)
+			free_cmd(ent);
 		return;
 	}