linux-kernel - [PATCH] net: Fix potential out of bound write in skb_try

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Date:   Tue, 4 Aug 2020 19:48:18 +0800
From:   linmiaohe <linmiaohe@...wei.com>
To:     <davem@...emloft.net>, <kuba@...nel.org>, <pshelar@....org>,
        <fw@...len.de>, <martin.varghese@...ia.com>, <willemb@...gle.com>,
        <edumazet@...gle.com>, <dcaratti@...hat.com>,
        <steffen.klassert@...unet.com>, <pabeni@...hat.com>,
        <shmulik@...anetworks.com>, <kyk.segfault@...il.com>
CC:     <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH] net: Fix potential out of bound write in skb_try_coalesce()

From: Miaohe Lin <linmiaohe@...wei.com>

The head_frag of skb would occupy one extra skb_frag_t. Take it into
account or out of bound write to skb frags may happen.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
---
 net/core/skbuff.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 8a0c39e4ab0a..b489ba201fac 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -5154,7 +5154,7 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
 		unsigned int offset;
 
 		if (to_shinfo->nr_frags +
-		    from_shinfo->nr_frags >= MAX_SKB_FRAGS)
+		    from_shinfo->nr_frags + 1 >= MAX_SKB_FRAGS)
 			return false;
 
 		if (skb_head_is_locked(from))
-- 
2.19.1