NET: Fix locking issues in PPP, 6pack, mkiss and strip line disciplines.

[ Upstream commit adeab1afb7de89555c69aab5ca21300c14af6369 ]

Guido Trentalancia reports:

I am trying to use the kiss driver in the Linux kernel that is being
shipped with Fedora 10 but unfortunately I get the following oops:

mkiss: AX.25 Multikiss, Hans Albas PE1AYX
mkiss: ax0: crc mode is auto.
ADDRCONF(NETDEV_CHANGE): ax0: link becomes ready
------------[ cut here ]------------
WARNING: at kernel/softirq.c:77 __local_bh_disable+0x2f/0x83() (Not
tainted)
[...]
unloaded: microcode]
Pid: 0, comm: swapper Not tainted 2.6.27.25-170.2.72.fc10.i686 #1
 [<c042ddfb>] warn_on_slowpath+0x65/0x8b
 [<c06ab62b>] ? _spin_unlock_irqrestore+0x22/0x38
 [<c04228b4>] ? __enqueue_entity+0xe3/0xeb
 [<c042431e>] ? enqueue_entity+0x203/0x20b
 [<c0424361>] ? enqueue_task_fair+0x3b/0x3f
 [<c041f88c>] ? resched_task+0x3a/0x6e
 [<c06ab62b>] ? _spin_unlock_irqrestore+0x22/0x38
 [<c06ab4e2>] ? _spin_lock_bh+0xb/0x16
 [<c043255b>] __local_bh_disable+0x2f/0x83
 [<c04325ba>] local_bh_disable+0xb/0xd
 [<c06ab4e2>] _spin_lock_bh+0xb/0x16
 [<f8b6f600>] mkiss_receive_buf+0x2fb/0x3a6 [mkiss]
 [<c0572a30>] flush_to_ldisc+0xf7/0x198
 [<c0572b12>] tty_flip_buffer_push+0x41/0x51
 [<f89477f2>] ftdi_process_read+0x375/0x4ad [ftdi_sio]
 [<f8947a5a>] ftdi_read_bulk_callback+0x130/0x138 [ftdi_sio]
 [<c05d4bec>] usb_hcd_giveback_urb+0x63/0x93
 [<c05ea290>] uhci_giveback_urb+0xe5/0x15f
 [<c05eaabf>] uhci_scan_schedule+0x52e/0x767
 [<c05f6288>] ? psmouse_handle_byte+0xc/0xe5
 [<c054df78>] ? acpi_ev_gpe_detect+0xd6/0xe1
 [<c05ec5b0>] uhci_irq+0x110/0x125
 [<c05d4834>] usb_hcd_irq+0x40/0xa3
 [<c0465313>] handle_IRQ_event+0x2f/0x64
 [<c046642b>] handle_level_irq+0x74/0xbe
 [<c04663b7>] ? handle_level_irq+0x0/0xbe
 [<c0406e6e>] do_IRQ+0xc7/0xfe
 [<c0405668>] common_interrupt+0x28/0x30
 [<c056821a>] ? acpi_idle_enter_simple+0x162/0x19d
 [<c0617f52>] cpuidle_idle_call+0x60/0x92
 [<c0403c61>] cpu_idle+0x101/0x134
 [<c069b1ba>] rest_init+0x4e/0x50
 =======================
---[ end trace b7cc8076093467ad ]---
------------[ cut here ]------------
WARNING: at kernel/softirq.c:136 _local_bh_enable_ip+0x3d/0xc4()
[...]
Pid: 0, comm: swapper Tainted: G        W 2.6.27.25-170.2.72.fc10.i686
 [<c042ddfb>] warn_on_slowpath+0x65/0x8b
 [<c06ab62b>] ? _spin_unlock_irqrestore+0x22/0x38
 [<c04228b4>] ? __enqueue_entity+0xe3/0xeb
 [<c042431e>] ? enqueue_entity+0x203/0x20b
 [<c0424361>] ? enqueue_task_fair+0x3b/0x3f
 [<c041f88c>] ? resched_task+0x3a/0x6e
 [<c06ab62b>] ? _spin_unlock_irqrestore+0x22/0x38
 [<c06ab4e2>] ? _spin_lock_bh+0xb/0x16
 [<f8b6f642>] ? mkiss_receive_buf+0x33d/0x3a6 [mkiss]
 [<c04325f9>] _local_bh_enable_ip+0x3d/0xc4
 [<c0432688>] local_bh_enable_ip+0x8/0xa
 [<c06ab54d>] _spin_unlock_bh+0x11/0x13
 [<f8b6f642>] mkiss_receive_buf+0x33d/0x3a6 [mkiss]
 [<c0572a30>] flush_to_ldisc+0xf7/0x198
 [<c0572b12>] tty_flip_buffer_push+0x41/0x51
 [<f89477f2>] ftdi_process_read+0x375/0x4ad [ftdi_sio]
 [<f8947a5a>] ftdi_read_bulk_callback+0x130/0x138 [ftdi_sio]
 [<c05d4bec>] usb_hcd_giveback_urb+0x63/0x93
 [<c05ea290>] uhci_giveback_urb+0xe5/0x15f
 [<c05eaabf>] uhci_scan_schedule+0x52e/0x767
 [<c05f6288>] ? psmouse_handle_byte+0xc/0xe5
 [<c054df78>] ? acpi_ev_gpe_detect+0xd6/0xe1
 [<c05ec5b0>] uhci_irq+0x110/0x125
 [<c05d4834>] usb_hcd_irq+0x40/0xa3
 [<c0465313>] handle_IRQ_event+0x2f/0x64
 [<c046642b>] handle_level_irq+0x74/0xbe
 [<c04663b7>] ? handle_level_irq+0x0/0xbe
 [<c0406e6e>] do_IRQ+0xc7/0xfe
 [<c0405668>] common_interrupt+0x28/0x30
 [<c056821a>] ? acpi_idle_enter_simple+0x162/0x19d
 [<c0617f52>] cpuidle_idle_call+0x60/0x92
 [<c0403c61>] cpu_idle+0x101/0x134
 [<c069b1ba>] rest_init+0x4e/0x50
 =======================
---[ end trace b7cc8076093467ad ]---
mkiss: ax0: Trying crc-smack
mkiss: ax0: Trying crc-flexnet

The issue was, that the locking code in mkiss was assuming it was only
ever being called in process or bh context.  Fixed by converting the
involved locking code to use irq-safe locks.

Review of other networking line disciplines shows that 6pack, both sync
and async PPP and STRIP have similar issues.  The ppp_async one is the
most interesting one as it sorts out half of the issue as far back as
2004 in commit http://git.kernel.org/?p=linux/kernel/git/tglx/history.git;a=commitdiff;h=2996d8deaeddd01820691a872550dc0cfba0c37d

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Reported-by: Guido Trentalancia <guido@trentalancia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 7 insertions, 4 deletions

diff --git a/drivers/net/ppp_async.c b/drivers/net/ppp_async.c
index 451bdb57d6f..7dac6317698 100644
--- a/drivers/net/ppp_async.c
+++ b/drivers/net/ppp_async.c
@@ -132,13 +132,15 @@ static DEFINE_RWLOCK(disc_data_lock);
 
 static struct asyncppp *ap_get(struct tty_struct *tty)
 {
+	unsigned long flags;
 	struct asyncppp *ap;
 
-	read_lock(&disc_data_lock);
+	read_lock_irqsave(&disc_data_lock, flags);
 	ap = tty->disc_data;
 	if (ap != NULL)
 		atomic_inc(&ap->refcnt);
-	read_unlock(&disc_data_lock);
+	read_unlock_irqrestore(&disc_data_lock, flags);
+
 	return ap;
 }
 
@@ -212,12 +214,13 @@ ppp_asynctty_open(struct tty_struct *tty)
 static void
 ppp_asynctty_close(struct tty_struct *tty)
 {
+	unsigned long flags;
 	struct asyncppp *ap;
 
-	write_lock_irq(&disc_data_lock);
+	write_lock_irqsave(&disc_data_lock, flags);
 	ap = tty->disc_data;
 	tty->disc_data = NULL;
-	write_unlock_irq(&disc_data_lock);
+	write_unlock_irqrestore(&disc_data_lock, flags);
 	if (!ap)
 		return;