| Message ID | 20220413181333.649424-1-eric.dumazet@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 9cb7c013420f98fa6fd12fc6a5dc055170c108db |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net] ipv6: make ip6_rt_gc_expire an atomic_t | expand |
On 4/13/22 12:13 PM, Eric Dumazet wrote: > From: Eric Dumazet <edumazet@google.com> > > 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: 1da177e4c3 ("Linux-2.6.12-rc2") > Signed-off-by: Eric Dumazet <edumazet@google.com> > Reported-by: syzbot <syzkaller@googlegroups.com> > --- > include/net/netns/ipv6.h | 4 ++-- > net/ipv6/route.c | 11 ++++++----- > 2 files changed, 8 insertions(+), 7 deletions(-) > Reviewed-by: David Ahern <dsahern@kernel.org>
Hello: This patch was applied to netdev/net.git (master) by Jakub Kicinski <kuba@kernel.org>: On Wed, 13 Apr 2022 11:13:33 -0700 you wrote: > From: Eric Dumazet <edumazet@google.com> > > 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. > > [...] Here is the summary with links: - [net] ipv6: make ip6_rt_gc_expire an atomic_t https://git.kernel.org/netdev/net/c/9cb7c013420f You are awesome, thank you!
diff --git a/include/net/netns/ipv6.h b/include/net/netns/ipv6.h index 3d83b64471d32391fb632e8c25e12a8ec7d1b42e..b4af4837d80b4ed47d05474432d5b8ebb42322e7 100644 --- a/include/net/netns/ipv6.h +++ b/include/net/netns/ipv6.h @@ -75,8 +75,8 @@ struct netns_ipv6 { struct list_head fib6_walkers; rwlock_t fib6_walker_lock; spinlock_t fib6_gc_lock; - unsigned int ip6_rt_gc_expire; - unsigned long ip6_rt_last_gc; + atomic_t ip6_rt_gc_expire; + unsigned long ip6_rt_last_gc; unsigned char flowlabel_has_excl; #ifdef CONFIG_IPV6_MULTIPLE_TABLES bool fib6_has_custom_rules; diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 169e9df6d172ead607cc20a108c3371a20dbc632..c4b6ce017d5e3bf63c66a53df3d46c08370aed23 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: