netdev - [PATCH net-next] net: add truesize debug checks in skb_{add|coalesce}_rx

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Message-ID: <20230913134841.3672509-1-edumazet@google.com>
Date: Wed, 13 Sep 2023 13:48:41 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next] net: add truesize debug checks in skb_{add|coalesce}_rx_frag()

It can be time consuming to track driver bugs, that might be detected
too late from this confusing warning in skb_try_coalesce()

	WARN_ON_ONCE(delta < len);

Add sanity check in skb_add_rx_frag() and skb_coalesce_rx_frag()
to better track bug origin for CONFIG_DEBUG_NET=y builds.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/core/skbuff.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 4eaf7ed0d1f44e8305109da2da2835013786a857..2198979470ecfaf5667aca7bdecfbf2aa569f852 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -847,6 +847,8 @@ EXPORT_SYMBOL(__napi_alloc_skb);
 void skb_add_rx_frag(struct sk_buff *skb, int i, struct page *page, int off,
 		     int size, unsigned int truesize)
 {
+	DEBUG_NET_WARN_ON_ONCE(size > truesize);
+
 	skb_fill_page_desc(skb, i, page, off, size);
 	skb->len += size;
 	skb->data_len += size;
@@ -859,6 +861,8 @@ void skb_coalesce_rx_frag(struct sk_buff *skb, int i, int size,
 {
 	skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
 
+	DEBUG_NET_WARN_ON_ONCE(size > truesize);
+
 	skb_frag_size_add(frag, size);
 	skb->len += size;
 	skb->data_len += size;
-- 
2.42.0.283.g2d96d420d3-goog