Messages in this thread Patch in this message | | | From | Christian Eggers <> | Subject | [PATCH] net: dsa: microchip: fix race condition | Date | Tue, 27 Oct 2020 20:45:34 +0100 |
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[ 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@arri.de> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com> Reviewed-by: Vladimir Oltean <olteanv@gmail.com> Signed-off-by: Jakub Kicinski <kuba@kernel.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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