| Message ID | 20220628121248.858695-1-edumazet@google.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 4e43e64d0f1332fcc503babad4dc31aead7131ca |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | ipv6: fix lockdep splat in in6_dump_addrs() | expand |
Hello: This patch was applied to netdev/net.git (master) by Jakub Kicinski <kuba@kernel.org>: On Tue, 28 Jun 2022 12:12:48 +0000 you wrote: > As reported by syzbot, we should not use rcu_dereference() > when rcu_read_lock() is not held. > > WARNING: suspicious RCU usage > 5.19.0-rc2-syzkaller #0 Not tainted > > net/ipv6/addrconf.c:5175 suspicious rcu_dereference_check() usage! > > [...] Here is the summary with links: - ipv6: fix lockdep splat in in6_dump_addrs() https://git.kernel.org/netdev/net/c/4e43e64d0f13 You are awesome, thank you!
On Tue, Jun 28, 2022 at 12:12:48PM +0000, Eric Dumazet wrote: > As reported by syzbot, we should not use rcu_dereference() > when rcu_read_lock() is not held. > Is the comment at the top of the function out of date? 5141 /* called with rcu_read_lock() */ ^^^^^^^^^^^^^^^^^^^^^^^^^^^ 5142 static int in6_dump_addrs(struct inet6_dev *idev, struct sk_buff *skb, 5143 struct netlink_callback *cb, int s_ip_idx, 5144 struct inet6_fill_args *fillargs) 5145 { regards, dan carpenter
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c index 5864cbc30db69bc61483b2557fdc201e1a20f0a0..49cc6587dd771ac0bb17fbc31402785bcdd8ff18 100644 --- a/net/ipv6/addrconf.c +++ b/net/ipv6/addrconf.c @@ -5168,9 +5168,9 @@ static int in6_dump_addrs(struct inet6_dev *idev, struct sk_buff *skb, fillargs->event = RTM_GETMULTICAST; /* multicast address */ - for (ifmca = rcu_dereference(idev->mc_list); + for (ifmca = rtnl_dereference(idev->mc_list); ifmca; - ifmca = rcu_dereference(ifmca->next), ip_idx++) { + ifmca = rtnl_dereference(ifmca->next), ip_idx++) { if (ip_idx < s_ip_idx) continue; err = inet6_fill_ifmcaddr(skb, ifmca, fillargs);
As reported by syzbot, we should not use rcu_dereference() when rcu_read_lock() is not held. WARNING: suspicious RCU usage 5.19.0-rc2-syzkaller #0 Not tainted net/ipv6/addrconf.c:5175 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 1 lock held by syz-executor326/3617: #0: ffffffff8d5848e8 (rtnl_mutex){+.+.}-{3:3}, at: netlink_dump+0xae/0xc20 net/netlink/af_netlink.c:2223 stack backtrace: CPU: 0 PID: 3617 Comm: syz-executor326 Not tainted 5.19.0-rc2-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 in6_dump_addrs+0x12d1/0x1790 net/ipv6/addrconf.c:5175 inet6_dump_addr+0x9c1/0xb50 net/ipv6/addrconf.c:5300 netlink_dump+0x541/0xc20 net/netlink/af_netlink.c:2275 __netlink_dump_start+0x647/0x900 net/netlink/af_netlink.c:2380 netlink_dump_start include/linux/netlink.h:245 [inline] rtnetlink_rcv_msg+0x73e/0xc90 net/core/rtnetlink.c:6046 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2501 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x543/0x7f0 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x917/0xe10 net/netlink/af_netlink.c:1921 sock_sendmsg_nosec net/socket.c:714 [inline] sock_sendmsg+0xcf/0x120 net/socket.c:734 ____sys_sendmsg+0x6eb/0x810 net/socket.c:2492 ___sys_sendmsg+0xf3/0x170 net/socket.c:2546 __sys_sendmsg net/socket.c:2575 [inline] __do_sys_sendmsg net/socket.c:2584 [inline] __se_sys_sendmsg net/socket.c:2582 [inline] __x64_sys_sendmsg+0x132/0x220 net/socket.c:2582 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x46/0xb0 Fixes: 88e2ca308094 ("mld: convert ifmcaddr6 to RCU") Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Taehee Yoo <ap420073@gmail.com> --- net/ipv6/addrconf.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)