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    Subject[PATCH 4.5 014/101] net/mlx5_core: Fix soft lockup in steering error flow
    Date
    4.5-stable review patch.  If anyone has any objections, please let me know.

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

    From: Maor Gottlieb <maorg@mellanox.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@mellanox.com>
    Reported-by: Amir Vadai <amir@vadai.me>
    Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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;

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