| Message ID | 20201005160829.5607-1-ceggers@arri.de |
|---|---|
| State | Superseded |
| Headers | show |
| Series | net: dsa: microchip: fix race condition | expand |
On 10/5/2020 9:08 AM, Christian Eggers wrote: > Between queuing the delayed work and finishing the setup of the dsa > ports, the process may sleep in request_module() and the queued work may > be executed prior the initialization of the DSA ports is finished. 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() make 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(). > > 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. > > Signed-off-by: Christian Eggers <ceggers@arri.de> > Cc: stable@vger.kernel.org This looks fine to me and the analysis appears to be correct, don't you need to pair the test for dev->mib_read_internal being non zero with setting it to zero in ksz_switch_unregister()? You would also most likely want to add a Fixes: tag such that this can be back ported to stable trees? > --- > 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 */ > > static void ksz_mib_read_work() > \--netif_carrier_ok(dp->slave); dp->slave has not been initialized yet > > > drivers/net/dsa/microchip/ksz_common.c | 16 +++++++++------- > 1 file changed, 9 insertions(+), 7 deletions(-) > > diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c > index 8e755b50c9c1..a94d2278b95c 100644 > --- a/drivers/net/dsa/microchip/ksz_common.c > +++ b/drivers/net/dsa/microchip/ksz_common.c > @@ -103,14 +103,8 @@ void ksz_init_mib_timer(struct ksz_device *dev) > > INIT_DELAYED_WORK(&dev->mib_read, ksz_mib_read_work); > > - /* Read MIB counters every 30 seconds to avoid overflow. */ > - dev->mib_read_interval = msecs_to_jiffies(30000); > - > for (i = 0; i < dev->mib_port_cnt; i++) > dev->dev_ops->port_init_cnt(dev, i); > - > - /* Start the timer 2 seconds later. */ > - schedule_delayed_work(&dev->mib_read, msecs_to_jiffies(2000)); > } > EXPORT_SYMBOL_GPL(ksz_init_mib_timer); > > @@ -143,7 +137,9 @@ void ksz_mac_link_down(struct dsa_switch *ds, int port, unsigned int mode, > > /* Read all MIB counters when the link is going down. */ > p->read = true; > - schedule_delayed_work(&dev->mib_read, 0); > + /* timer started */ > + if (dev->mib_read_interval) > + schedule_delayed_work(&dev->mib_read, 0); > } > EXPORT_SYMBOL_GPL(ksz_mac_link_down); > > @@ -446,6 +442,12 @@ 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. */ > + schedule_delayed_work(&dev->mib_read, 0); > + > return 0; > } > EXPORT_SYMBOL(ksz_switch_register); > -- Florian
diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c index 8e755b50c9c1..a94d2278b95c 100644 --- a/drivers/net/dsa/microchip/ksz_common.c +++ b/drivers/net/dsa/microchip/ksz_common.c @@ -103,14 +103,8 @@ void ksz_init_mib_timer(struct ksz_device *dev) INIT_DELAYED_WORK(&dev->mib_read, ksz_mib_read_work); - /* Read MIB counters every 30 seconds to avoid overflow. */ - dev->mib_read_interval = msecs_to_jiffies(30000); - for (i = 0; i < dev->mib_port_cnt; i++) dev->dev_ops->port_init_cnt(dev, i); - - /* Start the timer 2 seconds later. */ - schedule_delayed_work(&dev->mib_read, msecs_to_jiffies(2000)); } EXPORT_SYMBOL_GPL(ksz_init_mib_timer); @@ -143,7 +137,9 @@ void ksz_mac_link_down(struct dsa_switch *ds, int port, unsigned int mode, /* Read all MIB counters when the link is going down. */ p->read = true; - schedule_delayed_work(&dev->mib_read, 0); + /* timer started */ + if (dev->mib_read_interval) + schedule_delayed_work(&dev->mib_read, 0); } EXPORT_SYMBOL_GPL(ksz_mac_link_down); @@ -446,6 +442,12 @@ 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. */ + schedule_delayed_work(&dev->mib_read, 0); + return 0; } EXPORT_SYMBOL(ksz_switch_register);
Between queuing the delayed work and finishing the setup of the dsa ports, the process may sleep in request_module() and the queued work may be executed prior the initialization of the DSA ports is finished. 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() make 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(). 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. Signed-off-by: Christian Eggers <ceggers@arri.de> Cc: stable@vger.kernel.org --- 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 */ static void ksz_mib_read_work() \--netif_carrier_ok(dp->slave); dp->slave has not been initialized yet drivers/net/dsa/microchip/ksz_common.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)