Subject: [PATCH 12/18] net/tls: replace the sleeping lock around RX resync with a bit lock

From: Jakub Kicinski <[email-masked]>
Date: Tue, 4 Jun 2019 12:00:12 -0700

[ Upstream commit e52972c11d6b1262964db96d65934196db621685 ]

Commit 38030d7cb779 ("net/tls: avoid NULL-deref on resync during device removal")
tried to fix a potential NULL-dereference by taking the
context rwsem.  Unfortunately the RX resync may get called
from soft IRQ, so we can't use the rwsem to protect from
the device disappearing.  Because we are guaranteed there
can be only one resync at a time (it's called from strparser)
use a bit to indicate resync is busy and make device
removal wait for the bit to get cleared.

Note that there is a leftover "flags" field in struct
tls_context already.

Fixes: 4799ac81e52a ("tls: Add rx inline crypto offload")
Signed-off-by: Jakub Kicinski <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 include/net/tls.h    |  4 ++++
 net/tls/tls_device.c | 27 +++++++++++++++++++++------
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/include/net/tls.h b/include/net/tls.h
index c423b7d0b6ab..954110575891 100644
--- a/include/net/tls.h
+++ b/include/net/tls.h
@@ -161,6 +161,10 @@ enum {
 	TLS_PENDING_CLOSED_RECORD
 };
 
+enum tls_context_flags {
+	TLS_RX_SYNC_RUNNING = 0,
+};
+
 struct cipher_context {
 	u16 prepend_size;
 	u16 tag_size;
diff --git a/net/tls/tls_device.c b/net/tls/tls_device.c
index 8035bf495eb2..ead29c2aefa7 100644
--- a/net/tls/tls_device.c
+++ b/net/tls/tls_device.c
@@ -545,10 +545,22 @@ static int tls_device_push_pending_record(struct sock *sk, int flags)
 	return tls_push_data(sk, &msg_iter, 0, flags, TLS_RECORD_TYPE_DATA);
 }
 
+static void tls_device_resync_rx(struct tls_context *tls_ctx,
+				 struct sock *sk, u32 seq, u64 rcd_sn)
+{
+	struct net_device *netdev;
+
+	if (WARN_ON(test_and_set_bit(TLS_RX_SYNC_RUNNING, &tls_ctx->flags)))
+		return;
+	netdev = READ_ONCE(tls_ctx->netdev);
+	if (netdev)
+		netdev->tlsdev_ops->tls_dev_resync_rx(netdev, sk, seq, rcd_sn);
+	clear_bit_unlock(TLS_RX_SYNC_RUNNING, &tls_ctx->flags);
+}
+
 void handle_device_resync(struct sock *sk, u32 seq, u64 rcd_sn)
 {
 	struct tls_context *tls_ctx = tls_get_ctx(sk);
-	struct net_device *netdev = tls_ctx->netdev;
 	struct tls_offload_context_rx *rx_ctx;
 	u32 is_req_pending;
 	s64 resync_req;
@@ -563,10 +575,10 @@ void handle_device_resync(struct sock *sk, u32 seq, u64 rcd_sn)
 	is_req_pending = resync_req;
 
 	if (unlikely(is_req_pending) && req_seq == seq &&
-	    atomic64_try_cmpxchg(&rx_ctx->resync_req, &resync_req, 0))
-		netdev->tlsdev_ops->tls_dev_resync_rx(netdev, sk,
-						      seq + TLS_HEADER_SIZE - 1,
-						      rcd_sn);
+	    atomic64_try_cmpxchg(&rx_ctx->resync_req, &resync_req, 0)) {
+		seq += TLS_HEADER_SIZE - 1;
+		tls_device_resync_rx(tls_ctx, sk, seq, rcd_sn);
+	}
 }
 
 static int tls_device_reencrypt(struct sock *sk, struct sk_buff *skb)
@@ -954,7 +966,10 @@ static int tls_device_down(struct net_device *netdev)
 		if (ctx->rx_conf == TLS_HW)
 			netdev->tlsdev_ops->tls_dev_del(netdev, ctx,
 							TLS_OFFLOAD_CTX_DIR_RX);
-		ctx->netdev = NULL;
+		WRITE_ONCE(ctx->netdev, NULL);
+		smp_mb__before_atomic(); /* pairs with test_and_set_bit() */
+		while (test_bit(TLS_RX_SYNC_RUNNING, &ctx->flags))
+			usleep_range(10, 200);
 		dev_put(netdev);
 		list_del_init(&ctx->list);
 
-- 
2.20.1