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Message-ID: <20201027194534.23600-1-ceggers@arri.de>
Date: Tue, 27 Oct 2020 20:45:34 +0100
From: Christian Eggers <ceggers@...i.de>
To: "David S . Miller" <davem@...emloft.net>,
Andrew Lunn <andrew@...n.ch>,
Vivien Didelot <vivien.didelot@...il.com>,
Florian Fainelli <f.fainelli@...il.com>
CC: <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
Christian Eggers <ceggers@...i.de>,
Vladimir Oltean <olteanv@...il.com>,
Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH] net: dsa: microchip: fix race condition
[ Upstream commit 8098bd69bc4e925070313b1b95d03510f4f24738 ]
Between queuing the delayed work and finishing the setup of the dsa
ports, the process may sleep in request_module() (via
phy_device_create()) and the queued work may be executed prior to the
switch net devices being registered. In ksz_mib_read_work(), a NULL
dereference will happen within netof_carrier_ok(dp->slave).
Not queuing the delayed work in ksz_init_mib_timer() makes things even
worse because the work will now be queued for immediate execution
(instead of 2000 ms) in ksz_mac_link_down() via
dsa_port_link_register_of().
Call tree:
ksz9477_i2c_probe()
\--ksz9477_switch_register()
\--ksz_switch_register()
+--dsa_register_switch()
| \--dsa_switch_probe()
| \--dsa_tree_setup()
| \--dsa_tree_setup_switches()
| +--dsa_switch_setup()
| | +--ksz9477_setup()
| | | \--ksz_init_mib_timer()
| | | |--/* Start the timer 2 seconds later. */
| | | \--schedule_delayed_work(&dev->mib_read, msecs_to_jiffies(2000));
| | \--__mdiobus_register()
| | \--mdiobus_scan()
| | \--get_phy_device()
| | +--get_phy_id()
| | \--phy_device_create()
| | |--/* sleeping, ksz_mib_read_work() can be called meanwhile */
| | \--request_module()
| |
| \--dsa_port_setup()
| +--/* Called for non-CPU ports */
| +--dsa_slave_create()
| | +--/* Too late, ksz_mib_read_work() may be called beforehand */
| | \--port->slave = ...
| ...
| +--Called for CPU port */
| \--dsa_port_link_register_of()
| \--ksz_mac_link_down()
| +--/* mib_read must be initialized here */
| +--/* work is already scheduled, so it will be executed after 2000 ms */
| \--schedule_delayed_work(&dev->mib_read, 0);
\-- /* here port->slave is setup properly, scheduling the delayed work should be safe */
Solution:
1. Do not queue (only initialize) delayed work in ksz_init_mib_timer().
2. Only queue delayed work in ksz_mac_link_down() if init is completed.
3. Queue work once in ksz_switch_register(), after dsa_register_switch()
has completed.
Fixes: 7c6ff470aa86 ("net: dsa: microchip: add MIB counter reading support")
Signed-off-by: Christian Eggers <ceggers@...i.de>
Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
Reviewed-by: Vladimir Oltean <olteanv@...il.com>
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
This is a back port for 5.4. The original version has been applied to 5.8/5.9
a few hours ago.
Please decide whether the Reviewed-By: and Singed-off-by: tags shall be kept
or removed when forwarding this to stable.
regards
Christian
drivers/net/dsa/microchip/ksz_common.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)
diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
index 7fabc0e3d807..b1a9d1012fc4 100644
--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c
@@ -107,18 +107,11 @@ void ksz_init_mib_timer(struct ksz_device *dev)
{
int i;
- /* Read MIB counters every 30 seconds to avoid overflow. */
- dev->mib_read_interval = msecs_to_jiffies(30000);
-
INIT_WORK(&dev->mib_read, ksz_mib_read_work);
timer_setup(&dev->mib_read_timer, mib_monitor, 0);
for (i = 0; i < dev->mib_port_cnt; i++)
dev->dev_ops->port_init_cnt(dev, i);
-
- /* Start the timer 2 seconds later. */
- dev->mib_read_timer.expires = jiffies + msecs_to_jiffies(2000);
- add_timer(&dev->mib_read_timer);
}
EXPORT_SYMBOL_GPL(ksz_init_mib_timer);
@@ -152,7 +145,9 @@ void ksz_adjust_link(struct dsa_switch *ds, int port,
/* Read all MIB counters when the link is going down. */
if (!phydev->link) {
p->read = true;
- schedule_work(&dev->mib_read);
+ /* timer started */
+ if (dev->mib_read_interval)
+ schedule_work(&dev->mib_read);
}
mutex_lock(&dev->dev_mutex);
if (!phydev->link)
@@ -464,6 +459,13 @@ int ksz_switch_register(struct ksz_device *dev,
return ret;
}
+ /* Read MIB counters every 30 seconds to avoid overflow. */
+ dev->mib_read_interval = msecs_to_jiffies(30000);
+
+ /* Start the MIB timer. */
+ dev->mib_read_timer.expires = jiffies;
+ add_timer(&dev->mib_read_timer);
+
return 0;
}
EXPORT_SYMBOL(ksz_switch_register);
--
Christian Eggers
Embedded software developer
Arnold & Richter Cine Technik GmbH & Co. Betriebs KG
Sitz: Muenchen - Registergericht: Amtsgericht Muenchen - Handelsregisternummer: HRA 57918
Persoenlich haftender Gesellschafter: Arnold & Richter Cine Technik GmbH
Sitz: Muenchen - Registergericht: Amtsgericht Muenchen - Handelsregisternummer: HRB 54477
Geschaeftsfuehrer: Dr. Michael Neuhaeuser; Stephan Schenk; Walter Trauninger; Markus Zeiler
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