From a5397d68b2dbdb8f725ab2ff420171fbde39dbe5 Mon Sep 17 00:00:00 2001 From: Mark Bloch Date: Tue, 10 Aug 2021 03:43:05 +0000 Subject: net/sched: cls_api, reset flags on replay tc_new_tfilter() can replay a request if it got EAGAIN. The cited commit didn't account for this when it converted TC action ->init() API to use flags instead of parameters. This can lead to passing stale flags down the call chain which results in trying to lock rtnl when it's already locked, deadlocking the entire system. Fix by making sure to reset flags on each replay. ============================================ WARNING: possible recursive locking detected 5.14.0-rc3-custom-49011-g3d2bbb4f104d #447 Not tainted -------------------------------------------- tc/37605 is trying to acquire lock: ffffffff841df2f0 (rtnl_mutex){+.+.}-{3:3}, at: tc_setup_cb_add+0x14b/0x4d0 but task is already holding lock: ffffffff841df2f0 (rtnl_mutex){+.+.}-{3:3}, at: tc_new_tfilter+0xb12/0x22e0 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(rtnl_mutex); lock(rtnl_mutex); *** DEADLOCK *** May be due to missing lock nesting notation 1 lock held by tc/37605: #0: ffffffff841df2f0 (rtnl_mutex){+.+.}-{3:3}, at: tc_new_tfilter+0xb12/0x22e0 stack backtrace: CPU: 0 PID: 37605 Comm: tc Not tainted 5.14.0-rc3-custom-49011-g3d2bbb4f104d #447 Hardware name: Mellanox Technologies Ltd. MSN2010/SA002610, BIOS 5.6.5 08/24/2017 Call Trace: dump_stack_lvl+0x8b/0xb3 __lock_acquire.cold+0x175/0x3cb lock_acquire+0x1a4/0x4f0 __mutex_lock+0x136/0x10d0 fl_hw_replace_filter+0x458/0x630 [cls_flower] fl_change+0x25f2/0x4a64 [cls_flower] tc_new_tfilter+0xa65/0x22e0 rtnetlink_rcv_msg+0x86c/0xc60 netlink_rcv_skb+0x14d/0x430 netlink_unicast+0x539/0x7e0 netlink_sendmsg+0x84d/0xd80 ____sys_sendmsg+0x7ff/0x970 ___sys_sendmsg+0xf8/0x170 __sys_sendmsg+0xea/0x1b0 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x7f7b93b6c0a7 Code: 0c 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 2e 00 00 00 0f 05 <48> RSP: 002b:00007ffe365b3818 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f7b93b6c0a7 RDX: 0000000000000000 RSI: 00007ffe365b3880 RDI: 0000000000000003 RBP: 00000000610a75f6 R08: 0000000000000001 R09: 0000000000000000 R10: fffffffffffff3a9 R11: 0000000000000246 R12: 0000000000000001 R13: 0000000000000000 R14: 00007ffe365b7b58 R15: 00000000004822c0 Fixes: 695176bfe5de ("net_sched: refactor TC action init API") Signed-off-by: Mark Bloch Reviewed-by: Vlad Buslov Reviewed-by: Ido Schimmel Tested-by: Ido Schimmel Link: https://lore.kernel.org/r/20210810034305.63997-1-mbloch@nvidia.com Signed-off-by: Jakub Kicinski --- net/sched/cls_api.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'net/sched/cls_api.c') diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c index 69185e311422..4a7043a4e5d6 100644 --- a/net/sched/cls_api.c +++ b/net/sched/cls_api.c @@ -1949,7 +1949,7 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n, int err; int tp_created; bool rtnl_held = false; - u32 flags = 0; + u32 flags; if (!netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN)) return -EPERM; @@ -1970,6 +1970,7 @@ replay: tp = NULL; cl = 0; block = NULL; + flags = 0; if (prio == 0) { /* If no priority is provided by the user, -- cgit v1.2.3