Commit c540594f authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller
Browse files

bpf, mlx4: fix prog refcount in mlx4_en_try_alloc_resources error path 



Commit 67f8b1dc ("net/mlx4_en: Refactor the XDP forwarding rings
scheme") added a bug in that the prog's reference count is not dropped
in the error path when mlx4_en_try_alloc_resources() is failing from
mlx4_xdp_set().

We previously took bpf_prog_add(prog, priv->rx_ring_num - 1), that we
need to release again. Earlier in the call path, dev_change_xdp_fd()
itself holds a reference to the prog as well (hence the '- 1' in the
bpf_prog_add()), so a simple atomic_sub() is safe to use here. When
an error is propagated, then bpf_prog_put() is called eventually from
dev_change_xdp_fd()

Fixes: 67f8b1dc ("net/mlx4_en: Refactor the XDP forwarding rings scheme")
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b602e491

drivers/net/ethernet/mellanox/mlx4/en_netdev.c

+4 −1
Original line number Diff line number Diff line
@@ -2747,8 +2747,11 @@ static int mlx4_xdp_set(struct net_device *dev, struct bpf_prog *prog) 
	}



	err = mlx4_en_try_alloc_resources(priv, tmp, &new_prof);

	if (err)

	if (err) {

		if (prog)

			bpf_prog_sub(prog, priv->rx_ring_num - 1);

		goto unlock_out;

	}



	if (priv->port_up) {

		port_up = 1;

include/linux/bpf.h

+5 −0
Original line number Diff line number Diff line
@@ -234,6 +234,7 @@ 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);

void bpf_prog_sub(struct bpf_prog *prog, int i);

struct bpf_prog *bpf_prog_inc(struct bpf_prog *prog);

void bpf_prog_put(struct bpf_prog *prog);
@@ -303,6 +304,10 @@ static inline struct bpf_prog *bpf_prog_add(struct bpf_prog *prog, int i) 
	return ERR_PTR(-EOPNOTSUPP);

}



static inline void bpf_prog_sub(struct bpf_prog *prog, int i)

{

}



static inline void bpf_prog_put(struct bpf_prog *prog)

{

}

kernel/bpf/syscall.c

+11 −0
Original line number Diff line number Diff line
@@ -680,6 +680,17 @@ struct bpf_prog *bpf_prog_add(struct bpf_prog *prog, int i) 
}

EXPORT_SYMBOL_GPL(bpf_prog_add);



void bpf_prog_sub(struct bpf_prog *prog, int i)

{

	/* Only to be used for undoing previous bpf_prog_add() in some

	 * error path. We still know that another entity in our call

	 * path holds a reference to the program, thus atomic_sub() can

	 * be safely used in such cases!

	 */

	WARN_ON(atomic_sub_return(i, &prog->aux->refcnt) == 0);

}

EXPORT_SYMBOL_GPL(bpf_prog_sub);



struct bpf_prog *bpf_prog_inc(struct bpf_prog *prog)

{

	return bpf_prog_add(prog, 1);

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