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authorEric Dumazet <edumazet@google.com>2022-04-13 21:13:33 +0300
committerJakub Kicinski <kuba@kernel.org>2022-04-16 00:28:50 +0300
commit9cb7c013420f98fa6fd12fc6a5dc055170c108db (patch)
tree29c97668ccf730991b009998580b80c67adc28cd /net
parent268b41b34d9afd0e49bb266d5cca54c50abbe4c2 (diff)
downloadlinux-9cb7c013420f98fa6fd12fc6a5dc055170c108db.tar.xz
ipv6: make ip6_rt_gc_expire an atomic_t
Reads and Writes to ip6_rt_gc_expire always have been racy, as syzbot reported lately [1] There is a possible risk of under-flow, leading to unexpected high value passed to fib6_run_gc(), although I have not observed this in the field. Hosts hitting ip6_dst_gc() very hard are under pretty bad state anyway. [1] BUG: KCSAN: data-race in ip6_dst_gc / ip6_dst_gc read-write to 0xffff888102110744 of 4 bytes by task 13165 on cpu 1: ip6_dst_gc+0x1f3/0x220 net/ipv6/route.c:3311 dst_alloc+0x9b/0x160 net/core/dst.c:86 ip6_dst_alloc net/ipv6/route.c:344 [inline] icmp6_dst_alloc+0xb2/0x360 net/ipv6/route.c:3261 mld_sendpack+0x2b9/0x580 net/ipv6/mcast.c:1807 mld_send_cr net/ipv6/mcast.c:2119 [inline] mld_ifc_work+0x576/0x800 net/ipv6/mcast.c:2651 process_one_work+0x3d3/0x720 kernel/workqueue.c:2289 worker_thread+0x618/0xa70 kernel/workqueue.c:2436 kthread+0x1a9/0x1e0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 read-write to 0xffff888102110744 of 4 bytes by task 11607 on cpu 0: ip6_dst_gc+0x1f3/0x220 net/ipv6/route.c:3311 dst_alloc+0x9b/0x160 net/core/dst.c:86 ip6_dst_alloc net/ipv6/route.c:344 [inline] icmp6_dst_alloc+0xb2/0x360 net/ipv6/route.c:3261 mld_sendpack+0x2b9/0x580 net/ipv6/mcast.c:1807 mld_send_cr net/ipv6/mcast.c:2119 [inline] mld_ifc_work+0x576/0x800 net/ipv6/mcast.c:2651 process_one_work+0x3d3/0x720 kernel/workqueue.c:2289 worker_thread+0x618/0xa70 kernel/workqueue.c:2436 kthread+0x1a9/0x1e0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 value changed: 0x00000bb3 -> 0x00000ba9 Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 11607 Comm: kworker/0:21 Not tainted 5.18.0-rc1-syzkaller-00037-g42e7a03d3bad-dirty #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: mld mld_ifc_work Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Reviewed-by: David Ahern <dsahern@kernel.org> Link: https://lore.kernel.org/r/20220413181333.649424-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
-rw-r--r--net/ipv6/route.c11
1 files changed, 6 insertions, 5 deletions
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 169e9df6d172..c4b6ce017d5e 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3292,6 +3292,7 @@ static int ip6_dst_gc(struct dst_ops *ops)
int rt_elasticity = net->ipv6.sysctl.ip6_rt_gc_elasticity;
int rt_gc_timeout = net->ipv6.sysctl.ip6_rt_gc_timeout;
unsigned long rt_last_gc = net->ipv6.ip6_rt_last_gc;
+ unsigned int val;
int entries;
entries = dst_entries_get_fast(ops);
@@ -3302,13 +3303,13 @@ static int ip6_dst_gc(struct dst_ops *ops)
entries <= rt_max_size)
goto out;
- net->ipv6.ip6_rt_gc_expire++;
- fib6_run_gc(net->ipv6.ip6_rt_gc_expire, net, true);
+ fib6_run_gc(atomic_inc_return(&net->ipv6.ip6_rt_gc_expire), net, true);
entries = dst_entries_get_slow(ops);
if (entries < ops->gc_thresh)
- net->ipv6.ip6_rt_gc_expire = rt_gc_timeout>>1;
+ atomic_set(&net->ipv6.ip6_rt_gc_expire, rt_gc_timeout >> 1);
out:
- net->ipv6.ip6_rt_gc_expire -= net->ipv6.ip6_rt_gc_expire>>rt_elasticity;
+ val = atomic_read(&net->ipv6.ip6_rt_gc_expire);
+ atomic_set(&net->ipv6.ip6_rt_gc_expire, val - (val >> rt_elasticity));
return entries > rt_max_size;
}
@@ -6509,7 +6510,7 @@ static int __net_init ip6_route_net_init(struct net *net)
net->ipv6.sysctl.ip6_rt_min_advmss = IPV6_MIN_MTU - 20 - 40;
net->ipv6.sysctl.skip_notify_on_dev_down = 0;
- net->ipv6.ip6_rt_gc_expire = 30*HZ;
+ atomic_set(&net->ipv6.ip6_rt_gc_expire, 30*HZ);
ret = 0;
out: