Re: [PATCH net v3] tls: restrict device-down TX fallback to hardware TX sockets

[Rishikesh Jethwani]

On Tue, Nov 10, 2026 at 1:34 PM Jakub Kicinski <kuba@xxxxxxxxxx> wrote:
>
> On Wed,  4 Nov 2026 14:48:52 -0700 Rishikesh Jethwani wrote:
> > +             /* Stop offloaded TX and switch to the fallback.
> > +              * tls_is_skb_tx_device_offloaded will return false.
> > +              * Only HW TX sockets have the context it needs. Do it under
> > +              * tls_device_lock: the reference pins ctx, not ctx->sk.
> > +              */
> > +             if (ctx->tx_conf == TLS_HW)
> > +                     WRITE_ONCE(ctx->sk->sk_validate_xmit_skb,
> > +                                tls_validate_xmit_skb_sw);
>
> The locking in this patch looks way too coincidental.

Agreed. I'll split it in two.

Patch 1 drops tx_conf/rx_conf from tls_device_down(); they're set after
setup releases device_offload_lock. Setup instead publishes state before
up_read(): the HW validator for TX (device-down cmpxchg()es it and uses
the result for TX tls_dev_del()), and for RX it clears TLS_RX_DEV_CLOSED,
which starts set, after a successful add.

Patch 2 switches the validator under tls_device_lock. Since f08d8c1bb97c
("net/tls: Fix race in TLS device down flow") the destructor drops its
ctx reference under that lock, so a successful refcount_inc_not_zero()
there keeps ctx->sk allocated until unlock. We cannot unconditionally
use sock_hold(): sk_refcnt may already be zero while queued skbs keep
the socket allocated. TLS_TX_DEV_DOWN carries the result into cleanup
without touching ctx->sk again.

pw-bot: cr

> --
> pw-bot: cr