| Message ID | 20240801111842.50031-1-aha310510@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net] team: fix possible deadlock in team_port_change_check | expand |
On Thu, 1 Aug 2024 20:18:42 +0900 Jeongjun Park wrote: > struct team *team = port->team; > + bool flag = true; > > - mutex_lock(&team->lock); > + if (mutex_is_locked(&team->lock)){ > + unsigned long owner, curr = (unsigned long)current; > + owner = atomic_long_read(&team->lock.owner); > + if (owner != curr) > + mutex_lock(&team->lock); > + else > + flag = false; > + } > + else{ > + mutex_lock(&team->lock); > + } > __team_port_change_check(port, linkup); > - mutex_unlock(&team->lock); > + if (flag) > + mutex_unlock(&team->lock); You didn't even run this thru checkpatch, let alone the fact that its reimplementing nested locks (or trying to) :( Some of the syzbot reports are not fixed because they are either hard or because there is a long standing disagreement on how to solve them. Please keep that in mind.
Jakub Kicinski wrote: > > On Thu, 1 Aug 2024 20:18:42 +0900 Jeongjun Park wrote: > > struct team *team = port->team; > > + bool flag = true; > > > > - mutex_lock(&team->lock); > > + if (mutex_is_locked(&team->lock)){ > > + unsigned long owner, curr = (unsigned long)current; > > + owner = atomic_long_read(&team->lock.owner); > > + if (owner != curr) > > + mutex_lock(&team->lock); > > + else > > + flag = false; > > + } > > + else{ > > + mutex_lock(&team->lock); > > + } > > __team_port_change_check(port, linkup); > > - mutex_unlock(&team->lock); > > + if (flag) > > + mutex_unlock(&team->lock); > > You didn't even run this thru checkpatch, let alone the fact that its > reimplementing nested locks (or trying to) :( > > Some of the syzbot reports are not fixed because they are either hard > or because there is a long standing disagreement on how to solve them. > Please keep that in mind. Okay, but I have a question. Is it true that team devices can also be protected through rtnl? As far as I know, rtnl only protects net_device, so I didn't think about removing the lock for team->lock. Regards, Jeongjun Park
On Fri, 2 Aug 2024 07:51:19 +0900 Jeongjun Park wrote: > > You didn't even run this thru checkpatch, let alone the fact that its > > reimplementing nested locks (or trying to) :( > > > > Some of the syzbot reports are not fixed because they are either hard > > or because there is a long standing disagreement on how to solve them. > > Please keep that in mind. > > Okay, but I have a question. Is it true that team devices can also be > protected through rtnl? As far as I know, rtnl only protects net_device, > so I didn't think about removing the lock for team->lock. Yes, but I think that gets us into the "long standing disagreement" territory :) You may be able to find previous attempt to remove team->lock in the mailing list archive.
diff --git a/drivers/net/team/team_core.c b/drivers/net/team/team_core.c index ab1935a4aa2c..4ac6e55998ec 100644 --- a/drivers/net/team/team_core.c +++ b/drivers/net/team/team_core.c @@ -2946,10 +2946,22 @@ static void __team_port_change_port_removed(struct team_port *port) static void team_port_change_check(struct team_port *port, bool linkup) { struct team *team = port->team; + bool flag = true; - mutex_lock(&team->lock); + if (mutex_is_locked(&team->lock)){ + unsigned long owner, curr = (unsigned long)current; + owner = atomic_long_read(&team->lock.owner); + if (owner != curr) + mutex_lock(&team->lock); + else + flag = false; + } + else{ + mutex_lock(&team->lock); + } __team_port_change_check(port, linkup); - mutex_unlock(&team->lock); + if (flag) + mutex_unlock(&team->lock); }
In do_setlink() , do_set_master() is called when dev->flags does not have the IFF_UP flag set, so 'team->lock' is acquired and dev_open() is called, which generates the NETDEV_UP event. This causes a deadlock as it tries to acquire 'team->lock' again. To solve this, I modified team_port_change_check to check if 'team->lock' has already been acquired and not acquire the lock again if it has been acquired in the upper function. ============================================ WARNING: possible recursive locking detected 6.11.0-rc1-syzkaller-ge4fc196f5ba3-dirty #0 Not tainted -------------------------------------------- syz.0.15/5889 is trying to acquire lock: ffff8880231e4d40 (team->team_lock_key#2){+.+.}-{3:3}, at: team_port_change_check drivers/net/team/team_core.c:2950 [inline] ffff8880231e4d40 (team->team_lock_key#2){+.+.}-{3:3}, at: team_device_event+0x2c7/0x770 drivers/net/team/team_core.c:2973 but task is already holding lock: ffff8880231e4d40 (team->team_lock_key#2){+.+.}-{3:3}, at: team_add_slave+0x9c/0x20e0 drivers/net/team/team_core.c:1975 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(team->team_lock_key#2); lock(team->team_lock_key#2); *** DEADLOCK *** May be due to missing lock nesting notation 2 locks held by syz.0.15/5889: #0: ffffffff8fa1f4e8 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:79 [inline] #0: ffffffff8fa1f4e8 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x372/0xea0 net/core/rtnetlink.c:6644 #1: ffff8880231e4d40 (team->team_lock_key#2){+.+.}-{3:3}, at: team_add_slave+0x9c/0x20e0 drivers/net/team/team_core.c:1975 stack backtrace: CPU: 1 UID: 0 PID: 5889 Comm: syz.0.15 Not tainted 6.11.0-rc1-syzkaller-ge4fc196f5ba3-dirty #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Call Trace: <TASK> __dump_stack lib/dump_stack.c:93 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:119 check_deadlock kernel/locking/lockdep.c:3061 [inline] validate_chain kernel/locking/lockdep.c:3855 [inline] __lock_acquire+0x2167/0x3cb0 kernel/locking/lockdep.c:5142 lock_acquire kernel/locking/lockdep.c:5759 [inline] lock_acquire+0x1b1/0x560 kernel/locking/lockdep.c:5724 __mutex_lock_common kernel/locking/mutex.c:608 [inline] __mutex_lock+0x175/0x9c0 kernel/locking/mutex.c:752 team_port_change_check drivers/net/team/team_core.c:2950 [inline] team_device_event+0x2c7/0x770 drivers/net/team/team_core.c:2973 notifier_call_chain+0xb9/0x410 kernel/notifier.c:93 call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:1994 call_netdevice_notifiers_extack net/core/dev.c:2032 [inline] call_netdevice_notifiers net/core/dev.c:2046 [inline] __dev_notify_flags+0x12d/0x2e0 net/core/dev.c:8876 dev_change_flags+0x10c/0x160 net/core/dev.c:8914 vlan_device_event+0xdfc/0x2120 net/8021q/vlan.c:468 notifier_call_chain+0xb9/0x410 kernel/notifier.c:93 call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:1994 call_netdevice_notifiers_extack net/core/dev.c:2032 [inline] call_netdevice_notifiers net/core/dev.c:2046 [inline] dev_open net/core/dev.c:1515 [inline] dev_open+0x144/0x160 net/core/dev.c:1503 team_port_add drivers/net/team/team_core.c:1216 [inline] team_add_slave+0xacd/0x20e0 drivers/net/team/team_core.c:1976 do_set_master+0x1bc/0x230 net/core/rtnetlink.c:2701 do_setlink+0x306d/0x4060 net/core/rtnetlink.c:2907 __rtnl_newlink+0xc35/0x1960 net/core/rtnetlink.c:3696 rtnl_newlink+0x67/0xa0 net/core/rtnetlink.c:3743 rtnetlink_rcv_msg+0x3c7/0xea0 net/core/rtnetlink.c:6647 netlink_rcv_skb+0x16b/0x440 net/netlink/af_netlink.c:2550 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline] netlink_unicast+0x544/0x830 net/netlink/af_netlink.c:1357 netlink_sendmsg+0x8b8/0xd70 net/netlink/af_netlink.c:1901 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg net/socket.c:745 [inline] ____sys_sendmsg+0xab5/0xc90 net/socket.c:2597 ___sys_sendmsg+0x135/0x1e0 net/socket.c:2651 __sys_sendmsg+0x117/0x1f0 net/socket.c:2680 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fc07ed77299 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fc07fb7f048 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007fc07ef05f80 RCX: 00007fc07ed77299 RDX: 0000000000000000 RSI: 0000000020000600 RDI: 0000000000000012 RBP: 00007fc07ede48e6 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 000000000000000b R14: 00007fc07ef05f80 R15: 00007ffeb5c0d528 Reported-by: syzbot+b668da2bc4cb9670bf58@syzkaller.appspotmail.com Fixes: 3d249d4ca7d0 ("net: introduce ethernet teaming device") Signed-off-by: Jeongjun Park <aha310510@gmail.com> --- drivers/net/team/team_core.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) --