netdev - Re: [PATCH bpf-next 03/17] dev: add rcu_read_lock_bh_held() as a valid check when getting a RCU dev ref

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 10 Jun 2021 12:37:22 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
CC:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>,
        Hangbin Liu <liuhangbin@...il.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Magnus Karlsson <magnus.karlsson@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: Re: [PATCH bpf-next 03/17] dev: add rcu_read_lock_bh_held() as a
 valid check when getting a RCU dev ref

On Wed, Jun 09, 2021 at 12:33:12PM +0200, Toke Høiland-Jørgensen wrote:
> Some of the XDP helpers (in particular, xdp_do_redirect()) will get a
> struct net_device reference using dev_get_by_index_rcu(). These are called
> from a NAPI poll context, which means the RCU reference liveness is ensured
> by local_bh_disable(). Add rcu_read_lock_bh_held() as a condition to the
> RCU list traversal in dev_get_by_index_rcu() so lockdep understands that
> the dereferences are safe from *both* an rcu_read_lock() *and* with
> local_bh_disable().
> 
> Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
> ---
>  net/core/dev.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/core/dev.c b/net/core/dev.c
> index febb23708184..a499c5ffe4a5 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -1002,7 +1002,7 @@ struct net_device *dev_get_by_index_rcu(struct net *net, int ifindex)
>  	struct net_device *dev;
>  	struct hlist_head *head = dev_index_hash(net, ifindex);
>  
> -	hlist_for_each_entry_rcu(dev, head, index_hlist)
> +	hlist_for_each_entry_rcu(dev, head, index_hlist, rcu_read_lock_bh_held())
Is it needed?  hlist_for_each_entry_rcu() checks for
rcu_read_lock_any_held().  Did lockdep complain?