net/mlx5: FPGA, tls, hold rcu read lock a bit longer

[ Upstream commit 31634bf5dcc418b5b2cacd954394c0c4620db6a2 ]

To avoid use-after-free, hold the rcu read lock until we are done copying
flow data into the command buffer.

Fixes: ab412e1dd7db ("net/mlx5: Accel, add TLS rx offload routines")
Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/fpga/tls.c b/drivers/net/ethernet/mellanox/mlx5/core/fpga/tls.c
index 8de64e8..08aa726 100644 (file)
--- a/drivers/net/ethernet/mellanox/mlx5/core/fpga/tls.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/fpga/tls.c
@@ -217,22 +217,22 @@ int mlx5_fpga_tls_resync_rx(struct mlx5_core_dev *mdev, u32 handle, u32 seq,
        void *cmd;
        int ret;
 
-       rcu_read_lock();
-       flow = idr_find(&mdev->fpga->tls->rx_idr, ntohl(handle));
-       rcu_read_unlock();
-
-       if (!flow) {
-               WARN_ONCE(1, "Received NULL pointer for handle\n");
-               return -EINVAL;
-       }
-
        buf = kzalloc(size, GFP_ATOMIC);
        if (!buf)
                return -ENOMEM;
 
        cmd = (buf + 1);
 
+       rcu_read_lock();
+       flow = idr_find(&mdev->fpga->tls->rx_idr, ntohl(handle));
+       if (unlikely(!flow)) {
+               rcu_read_unlock();
+               WARN_ONCE(1, "Received NULL pointer for handle\n");
+               kfree(buf);
+               return -EINVAL;
+       }
        mlx5_fpga_tls_flow_to_cmd(flow, cmd);
+       rcu_read_unlock();
 
        MLX5_SET(tls_cmd, cmd, swid, ntohl(handle));
        MLX5_SET64(tls_cmd, cmd, tls_rcd_sn, be64_to_cpu(rcd_sn));