[PATCH bpf-next v2 4/8] bpf: offload: free prog->aux->offload when device disappears

[Jakub Kicinski]

All bpf offload operations should now be under bpf_devs_lock,
it's safe to free and clear the entire offload structure,
not only the netdev pointer.

__bpf_prog_offload_destroy() will no longer be called multiple
times.

Suggested-by: Alexei Starovoitov <a...@kernel.org>
Signed-off-by: Jakub Kicinski <jakub.kicin...@netronome.com>
Reviewed-by: Quentin Monnet <quentin.mon...@netronome.com>
Acked-by: Alexei Starovoitov <a...@kernel.org>
---
 kernel/bpf/offload.c | 23 +++++++++--------------
 1 file changed, 9 insertions(+), 14 deletions(-)

diff --git a/kernel/bpf/offload.c b/kernel/bpf/offload.c
index 2f2184408d31..60be15b9d8f1 100644
--- a/kernel/bpf/offload.c
+++ b/kernel/bpf/offload.c
@@ -75,12 +75,14 @@ int bpf_prog_offload_init(struct bpf_prog *prog, union 
bpf_attr *attr)
 static int __bpf_offload_ndo(struct bpf_prog *prog, enum bpf_netdev_command 
cmd,
                             struct netdev_bpf *data)
 {
-       struct net_device *netdev = prog->aux->offload->netdev;
+       struct bpf_dev_offload *offload = prog->aux->offload;
+       struct net_device *netdev;
 
        ASSERT_RTNL();
 
-       if (!netdev)
+       if (!offload)
                return -ENODEV;
+       netdev = offload->netdev;
        if (!netdev->netdev_ops->ndo_bpf)
                return -EOPNOTSUPP;
 
@@ -116,7 +118,7 @@ int bpf_prog_offload_verify_insn(struct bpf_verifier_env 
*env,
 
        down_read(&bpf_devs_lock);
        offload = env->prog->aux->offload;
-       if (offload->netdev)
+       if (offload)
                ret = offload->dev_ops->insn_hook(env, insn_idx, prev_insn_idx);
        up_read(&bpf_devs_lock);
 
@@ -128,31 +130,24 @@ static void __bpf_prog_offload_destroy(struct bpf_prog 
*prog)
        struct bpf_dev_offload *offload = prog->aux->offload;
        struct netdev_bpf data = {};
 
-       /* Caution - if netdev is destroyed before the program, this function
-        * will be called twice.
-        */
-
        data.offload.prog = prog;
 
        if (offload->dev_state)
                WARN_ON(__bpf_offload_ndo(prog, BPF_OFFLOAD_DESTROY, &data));
 
-       offload->dev_state = false;
        list_del_init(&offload->offloads);
-       offload->netdev = NULL;
+       kfree(offload);
+       prog->aux->offload = NULL;
 }
 
 void bpf_prog_offload_destroy(struct bpf_prog *prog)
 {
-       struct bpf_dev_offload *offload = prog->aux->offload;
-
        rtnl_lock();
        down_write(&bpf_devs_lock);
-       __bpf_prog_offload_destroy(prog);
+       if (prog->aux->offload)
+               __bpf_prog_offload_destroy(prog);
        up_write(&bpf_devs_lock);
        rtnl_unlock();
-
-       kfree(offload);
 }
 
 static int bpf_prog_offload_translate(struct bpf_prog *prog)
-- 
2.15.1