Patch "ppp: fix lockdep splat in ppp_dev_uninit()" has been added to the 4.2-stable tree
Subsystems (3)
This is a note to let you know that I've just added the patch titled
ppp: fix lockdep splat in ppp_dev_uninit()
to the 4.2-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ppp-fix-lockdep-splat-in-ppp_dev_uninit.patch
and it can be found in the queue-4.2 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.
Quoted 1 line
From foo@baz Wed Sep 30 05:25:07 CEST 2015
From: Guillaume Nault <[email protected]>
Date: Thu, 24 Sep 2015 12:54:01 +0200
Subject: ppp: fix lockdep splat in ppp_dev_uninit()
From: Guillaume Nault <[email protected]>
[ Upstream commit 58a89ecaca53736aa465170530acea4f8be34ab4 ]
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 ***--- drivers/net/ppp/ppp_generic.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
drivers/net/ppp/ppp_generic.c +3 -1
@@ -2742,6 +2742,7 @@ static struct ppp *ppp_create_interface(*/ dev_net_set (dev, net); +rtnl_lock ();mutex_lock (&pn->all_ppp_mutex);if (unit <0 ) {
@@ -2772,7 +2773,7 @@ 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",
@@ -2784,6 +2785,7 @@ static struct ppp *ppp_create_interface(atomic_inc (&ppp_unit_count);mutex_unlock (&pn->all_ppp_mutex); +rtnl_unlock (); *retp =0 ;return ppp;
Patches currently in stable-queue which might be from [email protected] are
queue-4.2/ppp-fix-lockdep-splat-in-ppp_dev_uninit.patch