netdev - Re: [PATCH net 1/2] net/tls: Protect from calling tls_dev

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Date:   Wed, 25 Nov 2020 14:14:53 -0800
From:   Saeed Mahameed <saeed@...nel.org>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Maxim Mikityanskiy <maximmi@...lanox.com>
Subject: Re: [PATCH net 1/2] net/tls: Protect from calling tls_dev_del for
 TLS RX twice

On Wed, 2020-11-18 at 17:13 -0800, Jakub Kicinski wrote:
> On Tue, 17 Nov 2020 12:33:54 -0800 Saeed Mahameed wrote:
> > From: Maxim Mikityanskiy <maximmi@...lanox.com>
> > 
> > tls_device_offload_cleanup_rx doesn't clear tls_ctx->netdev after
> > calling tls_dev_del if TLX TX offload is also enabled. Clearing
> > tls_ctx->netdev gets postponed until tls_device_gc_task. It leaves
> > a
> > time frame when tls_device_down may get called and call tls_dev_del
> > for
> > RX one extra time, confusing the driver, which may lead to a crash.
> > 
> > This patch corrects this racy behavior by adding a flag to prevent
> > tls_device_down from calling tls_dev_del the second time.
> > 
> > Fixes: e8f69799810c ("net/tls: Add generic NIC offload
> > infrastructure")
> > Signed-off-by: Maxim Mikityanskiy <maximmi@...lanox.com>
> > Signed-off-by: Saeed Mahameed <saeedm@...dia.com>
> > ---
> > For -stable: 5.3
> > 
> >  include/net/tls.h    | 1 +
> >  net/tls/tls_device.c | 3 ++-
> >  2 files changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/net/tls.h b/include/net/tls.h
> > index baf1e99d8193..a0deddfde412 100644
> > --- a/include/net/tls.h
> > +++ b/include/net/tls.h
> > @@ -199,6 +199,7 @@ enum tls_context_flags {
> >  	 * to be atomic.
> >  	 */
> >  	TLS_TX_SYNC_SCHED = 1,
> 
> Please add a comment here explaining that this bit is set when device
> state is partially released, and ctx->netdev cannot be cleared but RX
> side was already removed.
> 
> > +	TLS_RX_DEV_RELEASED = 2,
> >  };
> >  
> >  struct cipher_context {
> > diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
> > index cec86229a6a0..b2261caac6be 100644
> > --- a/net/tls/tls_device.c
> > +++ b/net/tls/tls_device.c
> > @@ -1241,6 +1241,7 @@ void tls_device_offload_cleanup_rx(struct
> > sock *sk)
> >  
> >  	netdev->tlsdev_ops->tls_dev_del(netdev, tls_ctx,
> >  					TLS_OFFLOAD_CTX_DIR_RX);
> > +	set_bit(TLS_RX_DEV_RELEASED, &tls_ctx->flags);
> 
> Would the semantics of the bit be clearer if we only set the bit in
> an
> else branch below and renamed it TLS_RX_DEV_CLOSED?
> 
> Otherwise it could be confusing to the reader that his bit is only
> set
> here but not in tls_device_down().
> 

Thanks Jakub, Maxim handled both comments, I will send V2 and drop the
other patch !