From: Sasha Levin <sashal@kernel.org>
To: stable@vger.kernel.org
Cc: Jianbo Liu <jianbol@nvidia.com>,
	Cosmin Ratiu <cratiu@nvidia.com>,
	Steffen Klassert <steffen.klassert@secunet.com>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.15.y 1/4] xfrm: hold device only for the asynchronous decryption
Date: Tue, 22 Sep 2026 14:34:39 -0400
Message-ID: <20260922183442.3692649-1-sashal@kernel.org>
In-Reply-To: <2026092228-detective-absolute-febb@gregkh>
References: <2026092228-detective-absolute-febb@gregkh>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

From: Jianbo Liu <jianbol@nvidia.com>

[ Upstream commit b05d42eefac737ce3cd80114d3579111023941b8 ]

The dev_hold() on skb->dev during packet reception was originally
added to prevent the device from being released prematurely during
asynchronous decryption operations.

As current hardware can offload decryption, this asynchronous path is
not always utilized. This often results in a pattern of dev_hold()
immediately followed by dev_put() for each packet, creating
unnecessary reference counting overhead detrimental to performance.

This patch optimizes this by skipping the dev_hold() and subsequent
dev_put() when asynchronous decryption is not being performed.

Signed-off-by: Jianbo Liu <jianbol@nvidia.com>
Reviewed-by: Cosmin Ratiu <cratiu@nvidia.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Stable-dep-of: 3cf5cdecd99c ("xfrm: save input state data before secpath resets")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/xfrm/xfrm_input.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c
index 6ab0b2166a595..31a677073fd3a 100644
--- a/net/xfrm/xfrm_input.c
+++ b/net/xfrm/xfrm_input.c
@@ -504,6 +504,7 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 		/* An encap_type of -1 indicates async resumption. */
 		if (encap_type == -1) {
 			async = 1;
+			dev_put(skb->dev);
 			seq = XFRM_SKB_CB(skb)->seq.input.low;
 			goto resume;
 		}
@@ -643,18 +644,18 @@ int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 		XFRM_SKB_CB(skb)->seq.input.low = seq;
 		XFRM_SKB_CB(skb)->seq.input.hi = seq_hi;
 
-		dev_hold(skb->dev);
-
-		if (crypto_done)
+		if (crypto_done) {
 			nexthdr = x->type_offload->input_tail(x, skb);
-		else
+		} else {
+			dev_hold(skb->dev);
+
 			nexthdr = x->type->input(x, skb);
+			if (nexthdr == -EINPROGRESS)
+				return 0;
 
-		if (nexthdr == -EINPROGRESS)
-			return 0;
+			dev_put(skb->dev);
+		}
 resume:
-		dev_put(skb->dev);
-
 		spin_lock(&x->lock);
 		if (nexthdr < 0) {
 			if (nexthdr == -EBADMSG) {
-- 
2.53.0