netdev - [PATCH net-next 1/2] net: move the hsize check to the else block in skb

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Message-Id: <a34a8dcde6a158c64b0478c7098da757a6690f0b.1610368918.git.lucien.xin@gmail.com>
Date:   Mon, 11 Jan 2021 20:45:13 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org
Cc:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Neil Horman <nhorman@...driver.com>, davem@...emloft.net,
        Jakub Kicinski <kuba@...nel.org>,
        Alexander Duyck <alexander.duyck@...il.com>
Subject: [PATCH net-next 1/2] net: move the hsize check to the else block in skb_segment

After commit 89319d3801d1 ("net: Add frag_list support to skb_segment"),
it goes to process frag_list when !hsize in skb_segment(). However, when
using skb frag_list, sg normally should not be set. In this case, hsize
will be set with len right before !hsize check, then it won't go to
frag_list processing code.

So the right thing to do is move the hsize check to the else block, so
that it won't affect the !hsize check for frag_list processing.

Signed-off-by: Xin Long <lucien.xin@...il.com>
---
 net/core/skbuff.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 7626a33..ea79359 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3855,8 +3855,6 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
 		hsize = skb_headlen(head_skb) - offset;
 		if (hsize < 0)
 			hsize = 0;
-		if (hsize > len || !sg)
-			hsize = len;
 
 		if (!hsize && i >= nfrags && skb_headlen(list_skb) &&
 		    (skb_headlen(list_skb) == len || sg)) {
@@ -3901,6 +3899,9 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
 			skb_release_head_state(nskb);
 			__skb_push(nskb, doffset);
 		} else {
+			if (hsize > len || !sg)
+				hsize = len;
+
 			nskb = __alloc_skb(hsize + doffset + headroom,
 					   GFP_ATOMIC, skb_alloc_rx_flag(head_skb),
 					   NUMA_NO_NODE);
-- 
2.1.0