From: Eric Dumazet edumazet@google.com
commit d95d6320ba7a51d61c097ffc3bcafcf70283414e upstream.
Because fib6_info_hw_flags_set() is called without any synchronization, all accesses to gi6->offload, fi->trap and fi->offload_failed need some basic protection like READ_ONCE()/WRITE_ONCE().
BUG: KCSAN: data-race in fib6_info_hw_flags_set / fib6_purge_rt
read to 0xffff8881087d5886 of 1 bytes by task 13953 on cpu 0: fib6_drop_pcpu_from net/ipv6/ip6_fib.c:1007 [inline] fib6_purge_rt+0x4f/0x580 net/ipv6/ip6_fib.c:1033 fib6_del_route net/ipv6/ip6_fib.c:1983 [inline] fib6_del+0x696/0x890 net/ipv6/ip6_fib.c:2028 __ip6_del_rt net/ipv6/route.c:3876 [inline] ip6_del_rt+0x83/0x140 net/ipv6/route.c:3891 __ipv6_dev_ac_dec+0x2b5/0x370 net/ipv6/anycast.c:374 ipv6_dev_ac_dec net/ipv6/anycast.c:387 [inline] __ipv6_sock_ac_close+0x141/0x200 net/ipv6/anycast.c:207 ipv6_sock_ac_close+0x79/0x90 net/ipv6/anycast.c:220 inet6_release+0x32/0x50 net/ipv6/af_inet6.c:476 __sock_release net/socket.c:650 [inline] sock_close+0x6c/0x150 net/socket.c:1318 __fput+0x295/0x520 fs/file_table.c:280 ____fput+0x11/0x20 fs/file_table.c:313 task_work_run+0x8e/0x110 kernel/task_work.c:164 tracehook_notify_resume include/linux/tracehook.h:189 [inline] exit_to_user_mode_loop kernel/entry/common.c:175 [inline] exit_to_user_mode_prepare+0x160/0x190 kernel/entry/common.c:207 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline] syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:300 do_syscall_64+0x50/0xd0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x44/0xae
write to 0xffff8881087d5886 of 1 bytes by task 1912 on cpu 1: fib6_info_hw_flags_set+0x155/0x3b0 net/ipv6/route.c:6230 nsim_fib6_rt_hw_flags_set drivers/net/netdevsim/fib.c:668 [inline] nsim_fib6_rt_add drivers/net/netdevsim/fib.c:691 [inline] nsim_fib6_rt_insert drivers/net/netdevsim/fib.c:756 [inline] nsim_fib6_event drivers/net/netdevsim/fib.c:853 [inline] nsim_fib_event drivers/net/netdevsim/fib.c:886 [inline] nsim_fib_event_work+0x284f/0x2cf0 drivers/net/netdevsim/fib.c:1477 process_one_work+0x3f6/0x960 kernel/workqueue.c:2307 worker_thread+0x616/0xa70 kernel/workqueue.c:2454 kthread+0x2c7/0x2e0 kernel/kthread.c:327 ret_from_fork+0x1f/0x30
value changed: 0x22 -> 0x2a
Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 1912 Comm: kworker/1:3 Not tainted 5.16.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events nsim_fib_event_work
Fixes: 0c5fcf9e249e ("IPv6: Add "offload failed" indication to routes") Fixes: bb3c4ab93e44 ("ipv6: Add "offload" and "trap" indications to routes") Signed-off-by: Eric Dumazet edumazet@google.com Cc: Amit Cohen amcohen@nvidia.com Cc: Ido Schimmel idosch@nvidia.com Reported-by: syzbot syzkaller@googlegroups.com Link: https://lore.kernel.org/r/20220216173217.3792411-2-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/netdevsim/fib.c | 4 ++-- include/net/ip6_fib.h | 10 ++++++---- net/ipv6/route.c | 19 ++++++++++--------- 3 files changed, 18 insertions(+), 15 deletions(-)
--- a/drivers/net/netdevsim/fib.c +++ b/drivers/net/netdevsim/fib.c @@ -623,14 +623,14 @@ static int nsim_fib6_rt_append(struct ns if (err) goto err_fib6_rt_nh_del;
- fib6_event->rt_arr[i]->trap = true; + WRITE_ONCE(fib6_event->rt_arr[i]->trap, true); }
return 0;
err_fib6_rt_nh_del: for (i--; i >= 0; i--) { - fib6_event->rt_arr[i]->trap = false; + WRITE_ONCE(fib6_event->rt_arr[i]->trap, false); nsim_fib6_rt_nh_del(fib6_rt, fib6_event->rt_arr[i]); } return err; --- a/include/net/ip6_fib.h +++ b/include/net/ip6_fib.h @@ -189,14 +189,16 @@ struct fib6_info { u32 fib6_metric; u8 fib6_protocol; u8 fib6_type; + + u8 offload; + u8 trap; + u8 offload_failed; + u8 should_flush:1, dst_nocount:1, dst_nopolicy:1, fib6_destroying:1, - offload:1, - trap:1, - offload_failed:1, - unused:1; + unused:4;
struct rcu_head rcu; struct nexthop *nh; --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -5767,11 +5767,11 @@ static int rt6_fill_node(struct net *net }
if (!dst) { - if (rt->offload) + if (READ_ONCE(rt->offload)) rtm->rtm_flags |= RTM_F_OFFLOAD; - if (rt->trap) + if (READ_ONCE(rt->trap)) rtm->rtm_flags |= RTM_F_TRAP; - if (rt->offload_failed) + if (READ_ONCE(rt->offload_failed)) rtm->rtm_flags |= RTM_F_OFFLOAD_FAILED; }
@@ -6229,19 +6229,20 @@ void fib6_info_hw_flags_set(struct net * struct sk_buff *skb; int err;
- if (f6i->offload == offload && f6i->trap == trap && - f6i->offload_failed == offload_failed) + if (READ_ONCE(f6i->offload) == offload && + READ_ONCE(f6i->trap) == trap && + READ_ONCE(f6i->offload_failed) == offload_failed) return;
- f6i->offload = offload; - f6i->trap = trap; + WRITE_ONCE(f6i->offload, offload); + WRITE_ONCE(f6i->trap, trap);
/* 2 means send notifications only if offload_failed was changed. */ if (net->ipv6.sysctl.fib_notify_on_flag_change == 2 && - f6i->offload_failed == offload_failed) + READ_ONCE(f6i->offload_failed) == offload_failed) return;
- f6i->offload_failed = offload_failed; + WRITE_ONCE(f6i->offload_failed, offload_failed);
if (!rcu_access_pointer(f6i->fib6_node)) /* The route was removed from the tree, do not send