linux-kernel - [PATCH net-next] xfrm6_tunnel: Fix spi check in __xfrm6_tunnel_alloc

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Date:   Wed, 19 Dec 2018 14:45:09 +0800
From:   YueHaibing <yuehaibing@...wei.com>
To:     <davem@...emloft.net>, <steffen.klassert@...unet.com>,
        <herbert@...dor.apana.org.au>, <kuznet@....inr.ac.ru>,
        <yoshfuji@...ux-ipv6.org>
CC:     <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
        YueHaibing <yuehaibing@...wei.com>
Subject: [PATCH net-next] xfrm6_tunnel: Fix spi check in __xfrm6_tunnel_alloc_spi

gcc warn this:

net/ipv6/xfrm6_tunnel.c:143 __xfrm6_tunnel_alloc_spi() warn:
 always true condition '(spi <= 4294967295) => (0-u32max <= u32max)'

'spi' is u32, which always not greater than XFRM6_TUNNEL_SPI_MAX
because of wrap around. So the second forloop will never reach.

Signed-off-by: YueHaibing <yuehaibing@...wei.com>
---
 net/ipv6/xfrm6_tunnel.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/ipv6/xfrm6_tunnel.c b/net/ipv6/xfrm6_tunnel.c
index 4a46df8..f5b4feb 100644
--- a/net/ipv6/xfrm6_tunnel.c
+++ b/net/ipv6/xfrm6_tunnel.c
@@ -144,6 +144,9 @@ static u32 __xfrm6_tunnel_alloc_spi(struct net *net, xfrm_address_t *saddr)
 		index = __xfrm6_tunnel_spi_check(net, spi);
 		if (index >= 0)
 			goto alloc_spi;
+
+		if (spi == XFRM6_TUNNEL_SPI_MAX)
+			break;
 	}
 	for (spi = XFRM6_TUNNEL_SPI_MIN; spi < xfrm6_tn->spi; spi++) {
 		index = __xfrm6_tunnel_spi_check(net, spi);
-- 
2.7.0