[PATCH net 1/3] bpf, mlx5: fix mlx5e_create_rq taking reference on prog

[Daniel Borkmann]

In mlx5e_create_rq(), when creating a new queue, we call bpf_prog_add() but
without checking the return value. bpf_prog_add() can fail, so we really
must check it. Take the reference right when we assign it to the rq from
priv->xdp_prog, and just drop the reference on error path. Destruction in
mlx5e_destroy_rq() looks good, though.

Fixes: 86994156c736 ("net/mlx5e: XDP fast RX drop bpf programs support")
Signed-off-by: Daniel Borkmann <dan...@iogearbox.net>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 14 +++++++++++---
 kernel/bpf/syscall.c                              |  1 +
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c 
b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index 84e8b25..2b83667 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -489,7 +489,16 @@ static int mlx5e_create_rq(struct mlx5e_channel *c,
        rq->channel = c;
        rq->ix      = c->ix;
        rq->priv    = c->priv;
+
        rq->xdp_prog = priv->xdp_prog;
+       if (rq->xdp_prog) {
+               rq->xdp_prog = bpf_prog_inc(rq->xdp_prog);
+               if (IS_ERR(rq->xdp_prog)) {
+                       err = PTR_ERR(rq->xdp_prog);
+                       rq->xdp_prog = NULL;
+                       goto err_rq_wq_destroy;
+               }
+       }
 
        rq->buff.map_dir = DMA_FROM_DEVICE;
        if (rq->xdp_prog)
@@ -566,12 +575,11 @@ static int mlx5e_create_rq(struct mlx5e_channel *c,
        rq->page_cache.head = 0;
        rq->page_cache.tail = 0;
 
-       if (rq->xdp_prog)
-               bpf_prog_add(rq->xdp_prog, 1);
-
        return 0;
 
 err_rq_wq_destroy:
+       if (rq->xdp_prog)
+               bpf_prog_put(rq->xdp_prog);
        mlx5_wq_destroy(&rq->wq_ctrl);
 
        return err;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 237f3d6..751e806 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -686,6 +686,7 @@ struct bpf_prog *bpf_prog_inc(struct bpf_prog *prog)
 {
        return bpf_prog_add(prog, 1);
 }
+EXPORT_SYMBOL_GPL(bpf_prog_inc);
 
 static struct bpf_prog *__bpf_prog_get(u32 ufd, enum bpf_prog_type *type)
 {
-- 
1.9.3