[PATCH 5.13 058/151] net: mvvp2: fix short frame size on s390

Greg Kroah-Hartman
2021-08-16T13:25:01Z

From: John Hubbard <jhubbard@nvidia.com>

[ Upstream commit 704e624f7b3e8a4fc1ce43fb564746d1d07b20c0 ]

On s390, the following build warning occurs:

drivers/net/ethernet/marvell/mvpp2/mvpp2.h:844:2: warning: overflow in
conversion from 'long unsigned int' to 'int' changes value from
'18446744073709551584' to '-32' [-Woverflow]
844 | ((total_size) - MVPP2_SKB_HEADROOM - MVPP2_SKB_SHINFO_SIZE)

This happens because MVPP2_SKB_SHINFO_SIZE, which is 320 bytes (which is
already 64-byte aligned) on some architectures, actually gets ALIGN'd up
to 512 bytes in the s390 case.

So then, when this is invoked:

MVPP2_RX_MAX_PKT_SIZE(MVPP2_BM_SHORT_FRAME_SIZE)

...that turns into:

704 - 224 - 512 == -32

...which is not a good frame size to end up with! The warning above is a
bit lucky: it notices a signed/unsigned bad behavior here, which leads
to the real problem of a frame that is too short for its contents.

Increase MVPP2_BM_SHORT_FRAME_SIZE by 32 (from 704 to 736), which is
just exactly big enough. (The other values can't readily be changed
without causing a lot of other problems.)

Fixes: 07dd0a7aae7f ("mvpp2: add basic XDP support")
Cc: Sven Auhagen <sven.auhagen@voleatech.de>
Cc: Matteo Croce <mcroce@microsoft.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/net/ethernet/marvell/mvpp2/mvpp2.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2.h b/drivers/net/ethernet/marvell/mvpp2/mvpp2.h
index 4a61c90003b5..722209a14f53 100644
--- a/drivers/net/ethernet/marvell/mvpp2/mvpp2.h
+++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2.h
@@ -938,7 +938,7 @@ enum mvpp22_ptp_packet_format {
#define MVPP2_BM_COOKIE_POOL_OFFS 8
#define MVPP2_BM_COOKIE_CPU_OFFS 24

-#define MVPP2_BM_SHORT_FRAME_SIZE 704 /* frame size 128 */
+#define MVPP2_BM_SHORT_FRAME_SIZE 736 /* frame size 128 */
#define MVPP2_BM_LONG_FRAME_SIZE 2240 /* frame size 1664 */
#define MVPP2_BM_JUMBO_FRAME_SIZE 10432 /* frame size 9856 */
/* BM short pool packet size
--
2.30.2