Merge branch 'mlx5-bpf-refcnt-fixes'

Daniel Borkmann says:

====================
Couple of BPF refcount fixes for mlx5

Various mlx5 bugs on eBPF refcount handling found during review.
Last patch in series adds a __must_check to BPF helpers to make
sure we won't run into it again w/o compiler complaining first.

v2 -> v3:

 - Just reworked patch 2/4 so we don't need bpf_prog_sub().
 - Rebased, rest as is.

v1 -> v2:

 - After discussion with Alexei, we agreed upon rebasing the
   patches against net-next.
 - Since net-next, I've also added the __must_check to enforce
   future users to check for errors.
 - Fixed up commit message #2.
 - Simplify assignment from patch #1 based on Saeed's feedback
   on previous set.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 33 insertions, 13 deletions

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index bd0732d5d219..695760878898 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -513,7 +513,13 @@ 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;
+
+	rq->xdp_prog = priv->xdp_prog ? bpf_prog_inc(priv->xdp_prog) : NULL;
+	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)
@@ -590,12 +596,11 @@ 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;
@@ -3139,11 +3144,21 @@ static int mlx5e_xdp_set(struct net_device *netdev, struct bpf_prog *prog)
 
 	if (was_opened && reset)
 		mlx5e_close_locked(netdev);
+	if (was_opened && !reset) {
+		/* num_channels is invariant here, so we can take the
+		 * batched reference right upfront.
+		 */
+		prog = bpf_prog_add(prog, priv->params.num_channels);
+		if (IS_ERR(prog)) {
+			err = PTR_ERR(prog);
+			goto unlock;
+		}
+	}
 
-	/* exchange programs */
+	/* exchange programs, extra prog reference we got from caller
+	 * as long as we don't fail from this point onwards.
+	 */
 	old_prog = xchg(&priv->xdp_prog, prog);
-	if (prog)
-		bpf_prog_add(prog, 1);
 	if (old_prog)
 		bpf_prog_put(old_prog);
 
@@ -3159,7 +3174,6 @@ static int mlx5e_xdp_set(struct net_device *netdev, struct bpf_prog *prog)
 	/* exchanging programs w/o reset, we update ref counts on behalf
 	 * of the channels RQs here.
 	 */
-	bpf_prog_add(prog, priv->params.num_channels);
 	for (i = 0; i < priv->params.num_channels; i++) {
 		struct mlx5e_channel *c = priv->channel[i];
 
@@ -3691,6 +3705,9 @@ static void mlx5e_nic_cleanup(struct mlx5e_priv *priv)
 
 	if (MLX5_CAP_GEN(mdev, vport_group_manager))
 		mlx5_eswitch_unregister_vport_rep(esw, 0);
+
+	if (priv->xdp_prog)
+		bpf_prog_put(priv->xdp_prog);
 }
 
 static int mlx5e_init_nic_rx(struct mlx5e_priv *priv)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 01c1487277b2..69d0a7f12a3b 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -233,14 +233,14 @@ void bpf_register_map_type(struct bpf_map_type_list *tl);
 
 struct bpf_prog *bpf_prog_get(u32 ufd);
 struct bpf_prog *bpf_prog_get_type(u32 ufd, enum bpf_prog_type type);
-struct bpf_prog *bpf_prog_add(struct bpf_prog *prog, int i);
+struct bpf_prog * __must_check bpf_prog_add(struct bpf_prog *prog, int i);
 void bpf_prog_sub(struct bpf_prog *prog, int i);
-struct bpf_prog *bpf_prog_inc(struct bpf_prog *prog);
+struct bpf_prog * __must_check bpf_prog_inc(struct bpf_prog *prog);
 void bpf_prog_put(struct bpf_prog *prog);
 
 struct bpf_map *bpf_map_get_with_uref(u32 ufd);
 struct bpf_map *__bpf_map_get(struct fd f);
-struct bpf_map *bpf_map_inc(struct bpf_map *map, bool uref);
+struct bpf_map * __must_check bpf_map_inc(struct bpf_map *map, bool uref);
 void bpf_map_put_with_uref(struct bpf_map *map);
 void bpf_map_put(struct bpf_map *map);
 int bpf_map_precharge_memlock(u32 pages);
@@ -299,7 +299,8 @@ static inline struct bpf_prog *bpf_prog_get_type(u32 ufd,
 {
 	return ERR_PTR(-EOPNOTSUPP);
 }
-static inline struct bpf_prog *bpf_prog_add(struct bpf_prog *prog, int i)
+static inline struct bpf_prog * __must_check bpf_prog_add(struct bpf_prog *prog,
+							  int i)
 {
 	return ERR_PTR(-EOPNOTSUPP);
 }
@@ -311,7 +312,8 @@ static inline void bpf_prog_sub(struct bpf_prog *prog, int i)
 static inline void bpf_prog_put(struct bpf_prog *prog)
 {
 }
-static inline struct bpf_prog *bpf_prog_inc(struct bpf_prog *prog)
+
+static inline struct bpf_prog * __must_check bpf_prog_inc(struct bpf_prog *prog)
 {
 	return ERR_PTR(-EOPNOTSUPP);
 }
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index ce1b7de7d72c..eb15498b8d55 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -696,6 +696,7 @@ 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)
 {