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Mon, 26 Oct 2026 18:52:09 -0700 (PDT) Received: from c7-smtp-2026.dev.purestorage.com ([208.88.159.128]) by smtp-relay.gmail.com with ESMTPS id 4fb4d7f45d1cf-6b4458fa8dcsm1689318a12.4.2026.10.26.18.52.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Oct 2026 18:52:09 -0700 (PDT) X-Relaying-Domain: purestorage.com Received: from dev-rjethwani.dev.purestorage.com (dev-rjethwani.dev.purestorage.com [10.17.2.234]) by c7-smtp-2026.dev.purestorage.com (Postfix) with ESMTP id A7E1E40146; Mon, 26 Oct 2026 19:52:07 -0600 (MDT) Received: by dev-rjethwani.dev.purestorage.com (Postfix, from userid 1557719937) id 9DA37DCE126; Mon, 26 Oct 2026 19:52:07 -0600 (MDT) From: Rishikesh Jethwani To: netdev@vger.kernel.org Cc: Rishikesh Jethwani , John Fastabend , Jakub Kicinski , Sabrina Dubroca , "David S. Miller" , Eric Dumazet , Paolo Abeni , Simon Horman , Alice Mikityanska , Tariq Toukan , Boris Pismenny , linux-kernel@vger.kernel.org Subject: [PATCH net v2] tls: restrict device-down TX fallback to hardware TX sockets Date: Mon, 26 Oct 2026 19:52:05 -0600 Message-ID: <20261027015205.2169253-1-rjethwani@purestorage.com> X-Mailer: git-send-email 2.50.1 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit tls_device_down() installs tls_validate_xmit_skb_sw() on every socket with hardware offload in either direction, but tls_sw_fallback() needs a hardware TX context in priv_ctx_tx. An RX-only socket's NULL priv_ctx_tx crashes the fallback on its next transmit, for instance after the device comes back up: BUG: kernel NULL pointer dereference, address: 0000000000000008 RIP: 0010:_raw_spin_lock_irqsave+0x31/0x60 tls_sw_fallback+0x11b/0x450 validate_xmit_skb.isra.0+0x14f/0x420 __dev_queue_xmit+0x5e8/0xf30 A software-TX socket's priv_ctx_tx is a tls_sw_context_tx, which the fallback would walk as a hardware context. Only install the fallback on hardware TX sockets. Today tx_conf alone cannot identify them from tls_device_down(): tls_set_device_offload() drops device_offload_lock before it publishes the validator, and do_tls_setsockopt_conf() stores tx_conf = TLS_HW later still, under lock_sock, which tls_device_down() does not take. That leaves two windows. A NETDEV_DOWN before the validator store installs the software fallback, only for the hardware validator to overwrite it with ctx->netdev already cleared. A NETDEV_DOWN after the validator store leaves the fallback in place. Both read tx_conf as TLS_BASE and skip tls_dev_del(TX) today, which the destructor never retries (tls_device_queue_ctx_destruction() only queues it while ctx->netdev is set), so the driver TX context leaks. Gating the fallback on tx_conf alone would make the second window a regression: the hardware validator would stay in place with ctx->netdev cleared, so tls_is_skb_tx_device_offloaded() keeps reporting offloaded. Set tx_conf to TLS_HW in tls_set_device_offload() before dropping device_offload_lock, and publish the validator there too, so tls_device_down() sees both or neither. rx_conf has the same window and leaks the driver RX context, as tls_device_offload_cleanup_rx() skips tls_dev_del() once ctx->netdev is NULL, so set it the same way in tls_set_device_offload_rx(). The unconditional fallback install, and its overwrite by the hardware validator, date from c55dcdd435aa; the TX and RX leaks from 4799ac81e52a. The NULL dereference was reproduced on an RX-only socket, which now survives an interface down/up cycle and keeps receiving TLS records. The software-TX case and the setsockopt/NETDEV_DOWN races are from code inspection only. Fixes: c55dcdd435aa ("net/tls: Fix use-after-free after the TLS device goes down and up") Fixes: 4799ac81e52a ("tls: Add rx inline crypto offload") Signed-off-by: Rishikesh Jethwani --- net/tls/tls_device.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c index 1a5f328d80a5..9e0863dd2f96 100644 --- a/net/tls/tls_device.c +++ b/net/tls/tls_device.c @@ -1176,13 +1176,15 @@ int tls_set_device_offload(struct sock *sk) goto release_lock; tls_device_attach(ctx, sk, netdev); - up_read(&device_offload_lock); /* following this assignment tls_is_skb_tx_device_offloaded * will return true and the context might be accessed - * by the netdev's xmit function. + * by the netdev's xmit function. Publish it and tx_conf under + * device_offload_lock so tls_device_down() sees both or neither. */ smp_store_release(&sk->sk_validate_xmit_skb, tls_validate_xmit_skb); + ctx->tx_conf = TLS_HW; + up_read(&device_offload_lock); dev_put(netdev); return 0; @@ -1258,6 +1260,11 @@ int tls_set_device_offload_rx(struct sock *sk, struct tls_context *ctx) goto free_sw_resources; tls_device_attach(ctx, sk, netdev); + /* do_tls_setsockopt_conf() stores rx_conf too, but only after + * device_offload_lock is dropped. Set it here so tls_device_down() + * sees TLS_HW and releases the driver RX context. + */ + ctx->rx_conf = TLS_HW; up_read(&device_offload_lock); dev_put(netdev); @@ -1326,10 +1333,17 @@ static int tls_device_down(struct net_device *netdev) spin_unlock_irqrestore(&tls_device_lock, flags); list_for_each_entry_safe(ctx, tmp, &list, list) { + bool tx_hw = ctx->tx_conf == TLS_HW; + /* Stop offloaded TX and switch to the fallback. * tls_is_skb_tx_device_offloaded will return false. + * Only HW TX sockets have the context the fallback needs. + * The single read above keeps the fallback and tls_dev_del() + * below in agreement. */ - WRITE_ONCE(ctx->sk->sk_validate_xmit_skb, tls_validate_xmit_skb_sw); + if (tx_hw) + WRITE_ONCE(ctx->sk->sk_validate_xmit_skb, + tls_validate_xmit_skb_sw); /* Stop the RX and TX resync. * tls_dev_resync must not be called after tls_dev_del. @@ -1346,7 +1360,7 @@ static int tls_device_down(struct net_device *netdev) synchronize_net(); /* Release the offload context on the driver side. */ - if (ctx->tx_conf == TLS_HW) + if (tx_hw) netdev->tlsdev_ops->tls_dev_del(netdev, ctx, TLS_OFFLOAD_CTX_DIR_TX); if (ctx->rx_conf == TLS_HW && -- 2.50.1