netdev - [PATCH net] sfc: fix ef100 design-param checking

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Date:   Wed, 12 Aug 2020 10:32:49 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     <linux-net-drivers@...arflare.com>, <davem@...emloft.net>
CC:     <netdev@...r.kernel.org>, Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH net] sfc: fix ef100 design-param checking

The handling of the RXQ/TXQ size granularity design-params had two
 problems: it had a 64-bit divide that didn't build on 32-bit platforms,
 and it could divide by zero if the NIC supplied 0 as the value of the
 design-param.  Fix both by checking for 0 and for a granularity bigger
 than our min-size; if the granularity <= EFX_MIN_DMAQ_SIZE then it fits
 in 32 bits, so we can cast it to u32 for the divide.

Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Edward Cree <ecree@...arflare.com>
---
I've only build-tested this, and then only on 64-bit, since our lab's
 cooling system can't cope with the heatwave and we keep having to shut
 everything down :(

 drivers/net/ethernet/sfc/ef100_nic.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/sfc/ef100_nic.c b/drivers/net/ethernet/sfc/ef100_nic.c
index 36598d0542ed..206d70f9d95b 100644
--- a/drivers/net/ethernet/sfc/ef100_nic.c
+++ b/drivers/net/ethernet/sfc/ef100_nic.c
@@ -979,7 +979,8 @@ static int ef100_process_design_param(struct efx_nic *efx,
 		 * EFX_MIN_DMAQ_SIZE is divisible by GRANULARITY.
 		 * This is very unlikely to fail.
 		 */
-		if (EFX_MIN_DMAQ_SIZE % reader->value) {
+		if (!reader->value || reader->value > EFX_MIN_DMAQ_SIZE ||
+		    EFX_MIN_DMAQ_SIZE % (u32)reader->value) {
 			netif_err(efx, probe, efx->net_dev,
 				  "%s size granularity is %llu, can't guarantee safety\n",
 				  reader->type == ESE_EF100_DP_GZ_RXQ_SIZE_GRANULARITY ? "RXQ" : "TXQ",