netdev - [PATCH v6 net-next 03/13] net: limit GSO_MAX

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Date:   Mon,  9 May 2022 20:32:09 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev <netdev@...r.kernel.org>,
        Alexander Duyck <alexanderduyck@...com>,
        Coco Li <lixiaoyan@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH v6 net-next 03/13] net: limit GSO_MAX_SIZE to 524280 bytes

From: Eric Dumazet <edumazet@...gle.com>

Make sure we will not overflow shinfo->gso_segs

Minimal TCP MSS size is 8 bytes, and shinfo->gso_segs
is a 16bit field.

TCP_MIN_GSO_SIZE is currently defined in include/net/tcp.h,
it seems cleaner to not bring tcp details into include/linux/netdevice.h

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/linux/netdevice.h | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 6150e3a7ce9dc743129d3f4f240329dd688b49a4..673c444aae874428b117df45dffcaf702ac72a47 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2262,14 +2262,17 @@ struct net_device {
 	const struct rtnl_link_ops *rtnl_link_ops;
 
 	/* for setting kernel sock attribute on TCP connection setup */
+#define GSO_MAX_SEGS		65535u
 #define GSO_LEGACY_MAX_SIZE	65536u
-#define GSO_MAX_SIZE		UINT_MAX
+/* TCP minimal MSS is 8 (TCP_MIN_GSO_SIZE),
+ * and shinfo->gso_segs is a 16bit field.
+ */
+#define GSO_MAX_SIZE		(8 * GSO_MAX_SEGS)
 
 	unsigned int		gso_max_size;
 #define TSO_LEGACY_MAX_SIZE	65536
 #define TSO_MAX_SIZE		UINT_MAX
 	unsigned int		tso_max_size;
-#define GSO_MAX_SEGS		65535
 	u16			gso_max_segs;
 #define TSO_MAX_SEGS		U16_MAX
 	u16			tso_max_segs;
-- 
2.36.0.512.ge40c2bad7a-goog