linux-kernel - [PATCH 4.5 014/101] net/mlx5_core: Fix soft lockup in steering error flow

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Message-Id: <20160517011506.878916034@linuxfoundation.org>
Date:	Mon, 16 May 2016 18:20:19 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Maor Gottlieb <maorg@...lanox.com>,
	Amir Vadai <amir@...ai.me>,
	Saeed Mahameed <saeedm@...lanox.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.5 014/101] net/mlx5_core: Fix soft lockup in steering error flow

4.5-stable review patch.  If anyone has any objections, please let me know.

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

From: Maor Gottlieb <maorg@...lanox.com>

[ Upstream commit c3f9bf628bc7edda298897d952f5e761137229c9 ]

In the error flow of adding flow rule to auto-grouped flow
table, we call to tree_remove_node.

tree_remove_node locks the node's parent, however the node's parent
is already locked by mlx5_add_flow_rule and this causes a deadlock.
After this patch, if we failed to add the flow rule, we unlock the
flow table before calling to tree_remove_node.

fixes: f0d22d187473 ('net/mlx5_core: Introduce flow steering autogrouped
flow table')
Signed-off-by: Maor Gottlieb <maorg@...lanox.com>
Reported-by: Amir Vadai <amir@...ai.me>
Signed-off-by: Saeed Mahameed <saeedm@...lanox.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/ethernet/mellanox/mlx5/core/fs_core.c |   46 ++++++++--------------
 1 file changed, 17 insertions(+), 29 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlx5/core/fs_core.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/fs_core.c
@@ -957,33 +957,6 @@ unlock_fg:
 	return rule;
 }
 
-static struct mlx5_flow_rule *add_rule_to_auto_fg(struct mlx5_flow_table *ft,
-						  u8 match_criteria_enable,
-						  u32 *match_criteria,
-						  u32 *match_value,
-						  u8 action,
-						  u32 flow_tag,
-						  struct mlx5_flow_destination *dest)
-{
-	struct mlx5_flow_rule *rule;
-	struct mlx5_flow_group *g;
-
-	g = create_autogroup(ft, match_criteria_enable, match_criteria);
-	if (IS_ERR(g))
-		return (void *)g;
-
-	rule = add_rule_fg(g, match_value,
-			   action, flow_tag, dest);
-	if (IS_ERR(rule)) {
-		/* Remove assumes refcount > 0 and autogroup creates a group
-		 * with a refcount = 0.
-		 */
-		tree_get_node(&g->node);
-		tree_remove_node(&g->node);
-	}
-	return rule;
-}
-
 struct mlx5_flow_rule *
 mlx5_add_flow_rule(struct mlx5_flow_table *ft,
 		   u8 match_criteria_enable,
@@ -1008,8 +981,23 @@ mlx5_add_flow_rule(struct mlx5_flow_tabl
 				goto unlock;
 		}
 
-	rule = add_rule_to_auto_fg(ft, match_criteria_enable, match_criteria,
-				   match_value, action, flow_tag, dest);
+	g = create_autogroup(ft, match_criteria_enable, match_criteria);
+	if (IS_ERR(g)) {
+		rule = (void *)g;
+		goto unlock;
+	}
+
+	rule = add_rule_fg(g, match_value,
+			   action, flow_tag, dest);
+	if (IS_ERR(rule)) {
+		/* Remove assumes refcount > 0 and autogroup creates a group
+		 * with a refcount = 0.
+		 */
+		unlock_ref_node(&ft->node);
+		tree_get_node(&g->node);
+		tree_remove_node(&g->node);
+		return rule;
+	}
 unlock:
 	unlock_ref_node(&ft->node);
 	return rule;