[PATCH v5 net-next 03/13] net: limit GSO_MAX_SIZE to 524280 bytes

From: Eric Dumazet <eric.dumazet@gmail.com>
To: "David S . Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>
Cc: netdev <netdev@vger.kernel.org>,
	Alexander Duyck <alexanderduyck@fb.com>,
	Coco Li <lixiaoyan@google.com>,
	Eric Dumazet <edumazet@google.com>,
	Eric Dumazet <eric.dumazet@gmail.com>
Subject: [PATCH v5 net-next 03/13] net: limit GSO_MAX_SIZE to 524280 bytes
Date: Mon,  9 May 2022 15:21:39 -0700	[thread overview]
Message-ID: <20220509222149.1763877-4-eric.dumazet@gmail.com> (raw)
In-Reply-To: <20220509222149.1763877-1-eric.dumazet@gmail.com>

From: Eric Dumazet <edumazet@google.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@google.com>
---
 include/linux/netdevice.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 9a34cc45b20a4465a9e1532c39f410b26604144f..2ef9254a9d3a57403f510d32194d8be6730b1645 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2263,12 +2263,17 @@ struct net_device {
 
 	/* for setting kernel sock attribute on TCP connection setup */
 #define GSO_LEGACY_MAX_SIZE	65536u
-#define GSO_MAX_SIZE		UINT_MAX
+#define GSO_MAX_SEGS		65535u
+
+/* 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

