linux-kernel - [PATCH 4.19 265/293] net/mlx5: Fix potential sleeping in atomic context

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Date:   Mon, 20 Sep 2021 18:43:47 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>,
        Maor Gottlieb <maorg@...dia.com>,
        Saeed Mahameed <saeedm@...dia.com>
Subject: [PATCH 4.19 265/293] net/mlx5: Fix potential sleeping in atomic context

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

commit ee27e330a953595903979ffdb84926843595a9fe upstream.

Fixes the below flow of sleeping in atomic context by releasing
the RCU lock before calling to free_match_list.

build_match_list() <- disables preempt
-> free_match_list()
   -> tree_put_node()
      -> down_write_ref_node() <- take write lock

Fixes: 693c6883bbc4 ("net/mlx5: Add hash table for flow groups in flow table")
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Maor Gottlieb <maorg@...dia.com>
Signed-off-by: Saeed Mahameed <saeedm@...dia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/net/ethernet/mellanox/mlx5/core/fs_core.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlx5/core/fs_core.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/fs_core.c
@@ -1558,9 +1558,9 @@ static int build_match_list(struct match
 
 		curr_match = kmalloc(sizeof(*curr_match), GFP_ATOMIC);
 		if (!curr_match) {
+			rcu_read_unlock();
 			free_match_list(match_head);
-			err = -ENOMEM;
-			goto out;
+			return -ENOMEM;
 		}
 		if (!tree_get_node(&g->node)) {
 			kfree(curr_match);
@@ -1569,7 +1569,6 @@ static int build_match_list(struct match
 		curr_match->g = g;
 		list_add_tail(&curr_match->list, &match_head->list);
 	}
-out:
 	rcu_read_unlock();
 	return err;
 }