linux-kernel - [PATCH] net: ipv6: route: Fix a sleep-in-atomic-context bug in ip6_convert

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Date:   Sat,  1 Sep 2018 19:19:58 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     davem@...emloft.net, kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] net: ipv6: route: Fix a sleep-in-atomic-context bug in ip6_convert_metrics()

The kernel module may sleep with holding a spinlock.

The function call paths (from bottom to top) in Linux-4.16 are:

[FUNC] kzalloc(GFP_KERNEL)
net/ipv6/route.c, 2430: 
	kzalloc in ip6_convert_metrics
net/ipv6/route.c, 2890: 
	ip6_convert_metrics in ip6_route_add
net/ipv6/addrconf.c, 2322: 
	ip6_route_add in addrconf_prefix_route
net/ipv6/addrconf.c, 3331: 
	addrconf_prefix_route in fixup_permanent_addr
net/ipv6/addrconf.c, 3354: 
	fixup_permanent_addr in addrconf_permanent_addr
net/ipv6/addrconf.c, 3358: 
	_raw_write_lock_bh in addrconf_permanent_addr

To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.

This bug is found by my static analysis tool DSAC.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 net/ipv6/route.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index ec18b3ce8b6d..d15e72def7c1 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -2742,7 +2742,7 @@ static int ip6_convert_metrics(struct net *net, struct fib6_info *rt,
 	if (!cfg->fc_mx)
 		return 0;
 
-	p = kzalloc(sizeof(*rt->fib6_metrics), GFP_KERNEL);
+	p = kzalloc(sizeof(*rt->fib6_metrics), GFP_ATOMIC);
 	if (unlikely(!p))
 		return -ENOMEM;
 
-- 
2.17.0