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Date: Wed, 13 Apr 2022 18:39:52 -0600 From: David Ahern <dsahern@...nel.org> To: Eric Dumazet <eric.dumazet@...il.com>, "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com> Cc: netdev <netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>, syzbot <syzkaller@...glegroups.com> Subject: Re: [PATCH net] ipv6: make ip6_rt_gc_expire an atomic_t On 4/13/22 12:13 PM, Eric Dumazet wrote: > From: Eric Dumazet <edumazet@...gle.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@...gle.com> > Reported-by: syzbot <syzkaller@...glegroups.com> > --- > include/net/netns/ipv6.h | 4 ++-- > net/ipv6/route.c | 11 ++++++----- > 2 files changed, 8 insertions(+), 7 deletions(-) > Reviewed-by: David Ahern <dsahern@...nel.org>
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