From: Taehee Yoo ap420073@gmail.com
commit 0e8b8d6a2d85344d80dda5beadd98f5f86e8d3d3 upstream.
dev->unlink_list is reused unless dev is deleted. So, list_del() should not be used. Due to using list_del(), dev->unlink_list can't be reused so that dev->nested_level update logic doesn't work. In order to fix this bug, list_del_init() should be used instead of list_del().
Test commands: ip link add bond0 type bond ip link add bond1 type bond ip link set bond0 master bond1 ip link set bond0 nomaster ip link set bond1 master bond0 ip link set bond1 nomaster
Splat looks like: [ 255.750458][ T1030] ============================================ [ 255.751967][ T1030] WARNING: possible recursive locking detected [ 255.753435][ T1030] 5.9.0-rc8+ #772 Not tainted [ 255.754553][ T1030] -------------------------------------------- [ 255.756047][ T1030] ip/1030 is trying to acquire lock: [ 255.757304][ T1030] ffff88811782a280 (&dev_addr_list_lock_key/1){+...}-{2:2}, at: dev_mc_sync_multiple+0xc2/0x150 [ 255.760056][ T1030] [ 255.760056][ T1030] but task is already holding lock: [ 255.761862][ T1030] ffff88811130a280 (&dev_addr_list_lock_key/1){+...}-{2:2}, at: bond_enslave+0x3d4d/0x43e0 [bonding] [ 255.764581][ T1030] [ 255.764581][ T1030] other info that might help us debug this: [ 255.766645][ T1030] Possible unsafe locking scenario: [ 255.766645][ T1030] [ 255.768566][ T1030] CPU0 [ 255.769415][ T1030] ---- [ 255.770259][ T1030] lock(&dev_addr_list_lock_key/1); [ 255.771629][ T1030] lock(&dev_addr_list_lock_key/1); [ 255.772994][ T1030] [ 255.772994][ T1030] *** DEADLOCK *** [ 255.772994][ T1030] [ 255.775091][ T1030] May be due to missing lock nesting notation [ 255.775091][ T1030] [ 255.777182][ T1030] 2 locks held by ip/1030: [ 255.778299][ T1030] #0: ffffffffb1f63250 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x2e4/0x8b0 [ 255.780600][ T1030] #1: ffff88811130a280 (&dev_addr_list_lock_key/1){+...}-{2:2}, at: bond_enslave+0x3d4d/0x43e0 [bonding] [ 255.783411][ T1030] [ 255.783411][ T1030] stack backtrace: [ 255.784874][ T1030] CPU: 7 PID: 1030 Comm: ip Not tainted 5.9.0-rc8+ #772 [ 255.786595][ T1030] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 [ 255.789030][ T1030] Call Trace: [ 255.789850][ T1030] dump_stack+0x99/0xd0 [ 255.790882][ T1030] __lock_acquire.cold.71+0x166/0x3cc [ 255.792285][ T1030] ? register_lock_class+0x1a30/0x1a30 [ 255.793619][ T1030] ? rcu_read_lock_sched_held+0x91/0xc0 [ 255.794963][ T1030] ? rcu_read_lock_bh_held+0xa0/0xa0 [ 255.796246][ T1030] lock_acquire+0x1b8/0x850 [ 255.797332][ T1030] ? dev_mc_sync_multiple+0xc2/0x150 [ 255.798624][ T1030] ? bond_enslave+0x3d4d/0x43e0 [bonding] [ 255.800039][ T1030] ? check_flags+0x50/0x50 [ 255.801143][ T1030] ? lock_contended+0xd80/0xd80 [ 255.802341][ T1030] _raw_spin_lock_nested+0x2e/0x70 [ 255.803592][ T1030] ? dev_mc_sync_multiple+0xc2/0x150 [ 255.804897][ T1030] dev_mc_sync_multiple+0xc2/0x150 [ 255.806168][ T1030] bond_enslave+0x3d58/0x43e0 [bonding] [ 255.807542][ T1030] ? __lock_acquire+0xe53/0x51b0 [ 255.808824][ T1030] ? bond_update_slave_arr+0xdc0/0xdc0 [bonding] [ 255.810451][ T1030] ? check_chain_key+0x236/0x5e0 [ 255.811742][ T1030] ? mutex_is_locked+0x13/0x50 [ 255.812910][ T1030] ? rtnl_is_locked+0x11/0x20 [ 255.814061][ T1030] ? netdev_master_upper_dev_get+0xf/0x120 [ 255.815553][ T1030] do_setlink+0x94c/0x3040 [ ... ]
Reported-by: syzbot+4a0f7bc34e3997a6c7df@syzkaller.appspotmail.com Fixes: 1fc70edb7d7b ("net: core: add nested_level variable in net_device") Signed-off-by: Taehee Yoo ap420073@gmail.com Link: https://lore.kernel.org/r/20201015162606.9377-1-ap420073@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/core/dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/core/dev.c +++ b/net/core/dev.c @@ -10134,7 +10134,7 @@ void netdev_run_todo(void) struct net_device *dev = list_first_entry(&unlink_list, struct net_device, unlink_list); - list_del(&dev->unlink_list); + list_del_init(&dev->unlink_list); dev->nested_level = dev->lower_level - 1; } #endif