[PATCH 4.9 10/96] ip6mr: Do not call __IP6_INC_STATS() from preemptible context

Greg Kroah-Hartman
2019-03-12T17:18:05Z

From: Ido Schimmel <idosch@mellanox.com>

[ Upstream commit 87c11f1ddbbad38ad8bad47af133a8208985fbdf ]

Similar to commit 44f49dd8b5a6 ("ipmr: fix possible race resulting from
improper usage of IP_INC_STATS_BH() in preemptible context."), we cannot
assume preemption is disabled when incrementing the counter and
accessing a per-CPU variable.

Preemption can be enabled when we add a route in process context that
corresponds to packets stored in the unresolved queue, which are then
forwarded using this route [1].

Fix this by using IP6_INC_STATS() which takes care of disabling
preemption on architectures where it is needed.

[1]
[ 157.451447] BUG: using __this_cpu_add() in preemptible [00000000] code: smcrouted/2314
[ 157.460409] caller is ip6mr_forward2+0x73e/0x10e0
[ 157.460434] CPU: 3 PID: 2314 Comm: smcrouted Not tainted 5.0.0-rc7-custom-03635-g22f2712113f1 #1336
[ 157.460449] Hardware name: Mellanox Technologies Ltd. MSN2100-CB2FO/SA001017, BIOS 5.6.5 06/07/2016
[ 157.460461] Call Trace:
[ 157.460486] dump_stack+0xf9/0x1be
[ 157.460553] check_preemption_disabled+0x1d6/0x200
[ 157.460576] ip6mr_forward2+0x73e/0x10e0
[ 157.460705] ip6_mr_forward+0x9a0/0x1510
[ 157.460771] ip6mr_mfc_add+0x16b3/0x1e00
[ 157.461155] ip6_mroute_setsockopt+0x3cb/0x13c0
[ 157.461384] do_ipv6_setsockopt.isra.8+0x348/0x4060
[ 157.462013] ipv6_setsockopt+0x90/0x110
[ 157.462036] rawv6_setsockopt+0x4a/0x120
[ 157.462058] __sys_setsockopt+0x16b/0x340
[ 157.462198] __x64_sys_setsockopt+0xbf/0x160
[ 157.462220] do_syscall_64+0x14d/0x610
[ 157.462349] entry_SYSCALL_64_after_hwframe+0x49/0xbe

Fixes: 0912ea38de61 ("[IPV6] MROUTE: Add stats in multicast routing module method ip6_mr_forward().")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reported-by: Amit Cohen <amitc@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/ipv6/ip6mr.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/net/ipv6/ip6mr.c
+++ b/net/ipv6/ip6mr.c
@@ -1992,10 +1992,10 @@ int ip6mr_compat_ioctl(struct sock *sk,

static inline int ip6mr_forward2_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
{
- __IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
- IPSTATS_MIB_OUTFORWDATAGRAMS);
- __IP6_ADD_STATS(net, ip6_dst_idev(skb_dst(skb)),
- IPSTATS_MIB_OUTOCTETS, skb->len);
+ IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
+ IPSTATS_MIB_OUTFORWDATAGRAMS);
+ IP6_ADD_STATS(net, ip6_dst_idev(skb_dst(skb)),
+ IPSTATS_MIB_OUTOCTETS, skb->len);
return dst_output(net, sk, skb);
}