[PATCH net] net/mlx5e: macsec: fix use-after-free of metadata_dst on RX SC delete

[Doruk Tan Ozturk]

macsec_del_rxsc_ctx() frees the RX SC metadata_dst via
metadata_dst_free(), which directly kfree()s the object and ignores the
dst_entry refcount. The MACsec RX offload datapath
mlx5e_macsec_offload_handle_rx_skb() takes a reference on this dst with
dst_hold() and attaches it to the skb via skb_dst_set(). If such an skb
is still in flight when the RX SC is deleted, the metadata_dst is freed
while the skb still references it; the subsequent dst_release() on skb
free then operates on already-freed memory.

Replace metadata_dst_free() with dst_release() so the metadata_dst is
freed only after the last reference is dropped. The dst subsystem frees
metadata_dst objects from dst_destroy() once the refcount reaches zero
(DST_METADATA is set by metadata_dst_alloc()).

Same class of bug and fix as commit c32b26aaa2f9 ("netfilter:
nft_tunnel: fix use-after-free on object destroy").

Fixes: 9b9e23c4dc2b ("net/mlx5e: MACsec, fix memory leak when MACsec device is deleted")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Doruk Tan Ozturk <doruk@xxxxxxx>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.c b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.c
index 71b3a059c964..2a4e7ed76d31 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.c
@@ -829,7 +829,7 @@ static void macsec_del_rxsc_ctx(struct mlx5e_macsec *macsec, struct mlx5e_macsec
 	 */
 	list_del_rcu(&rx_sc->rx_sc_list_element);
 	xa_erase(&macsec->sc_xarray, rx_sc->sc_xarray_element->fs_id);
-	metadata_dst_free(rx_sc->md_dst);
+	dst_release(&rx_sc->md_dst->dst);
 	kfree(rx_sc->sc_xarray_element);
 	kfree_rcu_mightsleep(rx_sc);
 }
-- 
2.43.0