Author: hselasky
Date: Fri Sep 16 11:57:48 2016
New Revision: 305877
URL: https://svnweb.freebsd.org/changeset/base/305877

Log:
  mlx5en: Fix duplicate mbuf free-by-code.
  
  When mlx5e_sq_xmit() returns an error code and the mbuf pointer is set,
  we should not free the mbuf, because the caller will keep the mbuf in
  the drbr. Make sure the mbuf pointer is correctly set upon function
  exit.
  
  Sponsored by: Mellanox Technologies
  MFC after:    1 week

Modified:
  head/sys/dev/mlx5/mlx5_en/mlx5_en_tx.c

Modified: head/sys/dev/mlx5/mlx5_en/mlx5_en_tx.c
==============================================================================
--- head/sys/dev/mlx5/mlx5_en/mlx5_en_tx.c      Fri Sep 16 11:55:38 2016        
(r305876)
+++ head/sys/dev/mlx5/mlx5_en/mlx5_en_tx.c      Fri Sep 16 11:57:48 2016        
(r305877)
@@ -224,10 +224,8 @@ mlx5e_sq_xmit(struct mlx5e_sq *sq, struc
                /* Send one multi NOP message instead of many */
                mlx5e_send_nop(sq, (pi + 1) * MLX5_SEND_WQEBB_NUM_DS);
                pi = ((~sq->pc) & sq->wq.sz_m1);
-               if (pi < (MLX5_SEND_WQE_MAX_WQEBBS - 1)) {
-                       m_freem(mb);
+               if (pi < (MLX5_SEND_WQE_MAX_WQEBBS - 1))
                        return (ENOMEM);
-               }
        }
 
        /* Setup local variables */
@@ -338,10 +336,8 @@ mlx5e_sq_xmit(struct mlx5e_sq *sq, struc
                    mb, segs, &nsegs, BUS_DMA_NOWAIT);
        }
        /* Catch errors */
-       if (err != 0) {
+       if (err != 0)
                goto tx_drop;
-       }
-       *mbp = mb;
 
        for (x = 0; x != nsegs; x++) {
                if (segs[x].ds_len == 0)
@@ -374,6 +370,7 @@ skip_dma:
                bus_dmamap_sync(sq->dma_tag, sq->mbuf[pi].dma_map, 
BUS_DMASYNC_PREWRITE);
 
        sq->stats.packets++;
+       *mbp = NULL;    /* safety clear */
        return (0);
 
 tx_drop:
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