| From: Guillaume Nault <g.nault@alphalink.fr> |
| Date: Thu, 24 Sep 2015 12:54:01 +0200 |
| Subject: ppp: fix lockdep splat in ppp_dev_uninit() |
| |
| commit 58a89ecaca53736aa465170530acea4f8be34ab4 upstream. |
| |
| ppp_dev_uninit() locks all_ppp_mutex while under rtnl mutex protection. |
| ppp_create_interface() must then lock these mutexes in that same order |
| to avoid possible deadlock. |
| |
| [ 120.880011] ====================================================== |
| [ 120.880011] [ INFO: possible circular locking dependency detected ] |
| [ 120.880011] 4.2.0 #1 Not tainted |
| [ 120.880011] ------------------------------------------------------- |
| [ 120.880011] ppp-apitest/15827 is trying to acquire lock: |
| [ 120.880011] (&pn->all_ppp_mutex){+.+.+.}, at: [<ffffffffa0145f56>] ppp_dev_uninit+0x64/0xb0 [ppp_generic] |
| [ 120.880011] |
| [ 120.880011] but task is already holding lock: |
| [ 120.880011] (rtnl_mutex){+.+.+.}, at: [<ffffffff812e4255>] rtnl_lock+0x12/0x14 |
| [ 120.880011] |
| [ 120.880011] which lock already depends on the new lock. |
| [ 120.880011] |
| [ 120.880011] |
| [ 120.880011] the existing dependency chain (in reverse order) is: |
| [ 120.880011] |
| [ 120.880011] -> #1 (rtnl_mutex){+.+.+.}: |
| [ 120.880011] [<ffffffff81073a6f>] lock_acquire+0xcf/0x10e |
| [ 120.880011] [<ffffffff813ab18a>] mutex_lock_nested+0x56/0x341 |
| [ 120.880011] [<ffffffff812e4255>] rtnl_lock+0x12/0x14 |
| [ 120.880011] [<ffffffff812d9d94>] register_netdev+0x11/0x27 |
| [ 120.880011] [<ffffffffa0147b17>] ppp_ioctl+0x289/0xc98 [ppp_generic] |
| [ 120.880011] [<ffffffff8113b367>] do_vfs_ioctl+0x4ea/0x532 |
| [ 120.880011] [<ffffffff8113b3fd>] SyS_ioctl+0x4e/0x7d |
| [ 120.880011] [<ffffffff813ad7d7>] entry_SYSCALL_64_fastpath+0x12/0x6f |
| [ 120.880011] |
| [ 120.880011] -> #0 (&pn->all_ppp_mutex){+.+.+.}: |
| [ 120.880011] [<ffffffff8107334e>] __lock_acquire+0xb07/0xe76 |
| [ 120.880011] [<ffffffff81073a6f>] lock_acquire+0xcf/0x10e |
| [ 120.880011] [<ffffffff813ab18a>] mutex_lock_nested+0x56/0x341 |
| [ 120.880011] [<ffffffffa0145f56>] ppp_dev_uninit+0x64/0xb0 [ppp_generic] |
| [ 120.880011] [<ffffffff812d5263>] rollback_registered_many+0x19e/0x252 |
| [ 120.880011] [<ffffffff812d5381>] rollback_registered+0x29/0x38 |
| [ 120.880011] [<ffffffff812d53fa>] unregister_netdevice_queue+0x6a/0x77 |
| [ 120.880011] [<ffffffffa0146a94>] ppp_release+0x42/0x79 [ppp_generic] |
| [ 120.880011] [<ffffffff8112d9f6>] __fput+0xec/0x192 |
| [ 120.880011] [<ffffffff8112dacc>] ____fput+0x9/0xb |
| [ 120.880011] [<ffffffff8105447a>] task_work_run+0x66/0x80 |
| [ 120.880011] [<ffffffff81001801>] prepare_exit_to_usermode+0x8c/0xa7 |
| [ 120.880011] [<ffffffff81001900>] syscall_return_slowpath+0xe4/0x104 |
| [ 120.880011] [<ffffffff813ad931>] int_ret_from_sys_call+0x25/0x9f |
| [ 120.880011] |
| [ 120.880011] other info that might help us debug this: |
| [ 120.880011] |
| [ 120.880011] Possible unsafe locking scenario: |
| [ 120.880011] |
| [ 120.880011] CPU0 CPU1 |
| [ 120.880011] ---- ---- |
| [ 120.880011] lock(rtnl_mutex); |
| [ 120.880011] lock(&pn->all_ppp_mutex); |
| [ 120.880011] lock(rtnl_mutex); |
| [ 120.880011] lock(&pn->all_ppp_mutex); |
| [ 120.880011] |
| [ 120.880011] *** DEADLOCK *** |
| |
| Fixes: 8cb775bc0a34 ("ppp: fix device unregistration upon netns deletion") |
| Reported-by: Sedat Dilek <sedat.dilek@gmail.com> |
| Tested-by: Sedat Dilek <sedat.dilek@gmail.com> |
| Signed-off-by: Guillaume Nault <g.nault@alphalink.fr> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Ben Hutchings <ben@decadent.org.uk> |
| --- |
| drivers/net/ppp/ppp_generic.c | 4 +++- |
| 1 file changed, 3 insertions(+), 1 deletion(-) |
| |
| --- a/drivers/net/ppp/ppp_generic.c |
| +++ b/drivers/net/ppp/ppp_generic.c |
| @@ -2736,6 +2736,7 @@ static struct ppp *ppp_create_interface( |
| */ |
| dev_net_set(dev, net); |
| |
| + rtnl_lock(); |
| mutex_lock(&pn->all_ppp_mutex); |
| |
| if (unit < 0) { |
| @@ -2766,7 +2767,7 @@ static struct ppp *ppp_create_interface( |
| ppp->file.index = unit; |
| sprintf(dev->name, "ppp%d", unit); |
| |
| - ret = register_netdev(dev); |
| + ret = register_netdevice(dev); |
| if (ret != 0) { |
| unit_put(&pn->units_idr, unit); |
| netdev_err(ppp->dev, "PPP: couldn't register device %s (%d)\n", |
| @@ -2778,6 +2779,7 @@ static struct ppp *ppp_create_interface( |
| |
| atomic_inc(&ppp_unit_count); |
| mutex_unlock(&pn->all_ppp_mutex); |
| + rtnl_unlock(); |
| |
| *retp = 0; |
| return ppp; |
