Re: [KJ][PATCH] Correct misc_register return code handling in several drivers

Neil Horman
2006-10-24T12:54:06Z

On Tue, Oct 24, 2006 at 01:34:34PM +1000, Benjamin Herrenschmidt wrote:
> On Mon, 2006-10-23 at 13:19 -0400, Neil Horman wrote:
> > Hey All-
> > Janitor patch to clean up return code handling and exit from failed
> > calls to misc_register accross several modules.
>
> The patch doesn't match the description... What are those INIT_LIST_HEAD
> things ? Is this something I've missed or is this a new requirement for
> all misc devices ? Can't it be statically initialized instead ?
>

The INIT_LIST_HEAD is there to prevent a potential oops on module removal.
misc_register, if it fails, leaves miscdevice.list unchanged. That means its
next and prev pointers contain NULL or garbage, when both pointers should contain
&miscdevice.list. If we don't do that, then there is a chance we will oops on
module removal when we do a list_del in misc_deregister on the moudule_exit
routine. I could have done this statically, but I thought it looked cleaner to
do it with the macro in the code.

Thanks & Regards
Neil

> > Thanks & Regards
> > Neil
> >
> > Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
> >
> >
> > drivers/char/mmtimer.c | 29 +++++++++++++++++++++++------
> > drivers/char/tpm/tpm.c | 1 +
> > drivers/input/misc/hp_sdc_rtc.c | 6 +++++-
> > drivers/macintosh/apm_emu.c | 5 ++++-
> > drivers/net/tun.c | 2 ++
> > fs/dlm/user.c | 1 +
> > 6 files changed, 36 insertions(+), 8 deletions(-)
> >
> >
> > diff --git a/drivers/char/mmtimer.c b/drivers/char/mmtimer.c
> > --- a/drivers/char/mmtimer.c
> > +++ b/drivers/char/mmtimer.c
> > @@ -669,6 +669,7 @@ static struct k_clock sgi_clock = {
> > static int __init mmtimer_init(void)
> > {
> > unsigned i;
> > + int err = -1;
> > cnodeid_t node, maxn = -1;
> >
> > if (!ia64_platform_is("sn2"))
> > @@ -680,7 +681,7 @@ static int __init mmtimer_init(void)
> > if (sn_rtc_cycles_per_second < 100000) {
> > printk(KERN_ERR "%s: unable to determine clock frequency\n",
> > MMTIMER_NAME);
> > - return -1;
> > + goto out;
> > }
> >
> > mmtimer_femtoperiod = ((unsigned long)1E15 + sn_rtc_cycles_per_second /
> > @@ -689,13 +690,13 @@ static int __init mmtimer_init(void)
> > if (request_irq(SGI_MMTIMER_VECTOR, mmtimer_interrupt, IRQF_PERCPU, MMTIMER_NAME, NULL)) {
> > printk(KERN_WARNING "%s: unable to allocate interrupt.",
> > MMTIMER_NAME);
> > - return -1;
> > + goto out;
> > }
> >
> > if (misc_register(&mmtimer_miscdev)) {
> > printk(KERN_ERR "%s: failed to register device\n",
> > MMTIMER_NAME);
> > - return -1;
> > + goto out1;
> > }
> >
> > /* Get max numbered node, calculate slots needed */
> > @@ -709,16 +710,18 @@ static int __init mmtimer_init(void)
> > if (timers == NULL) {
> > printk(KERN_ERR "%s: failed to allocate memory for device\n",
> > MMTIMER_NAME);
> > - return -1;
> > + goto out2;
> > }
> >
> > + memset(timers,0,(sizeof(mmtimer_t *)*maxn));
> > +
> > /* Allocate mmtimer_t's for each online node */
> > for_each_online_node(node) {
> > timers[node] = kmalloc_node(sizeof(mmtimer_t)*NUM_COMPARATORS, GFP_KERNEL, node);
> > if (timers[node] == NULL) {
> > printk(KERN_ERR "%s: failed to allocate memory for device\n",
> > MMTIMER_NAME);
> > - return -1;
> > + goto out3;
> > }
> > for (i=0; i< NUM_COMPARATORS; i++) {
> > mmtimer_t * base = timers[node] + i;
> > @@ -738,7 +741,21 @@ static int __init mmtimer_init(void)
> > printk(KERN_INFO "%s: v%s, %ld MHz\n", MMTIMER_DESC, MMTIMER_VERSION,
> > sn_rtc_cycles_per_second/(unsigned long)1E6);
> >
> > - return 0;
> > + err = 0;
> > +out:
> > + return err;
> > +
> > +out3:
> > + for_each_online_node(node) {
> > + if(timers[node] != NULL)
> > + kfree(timers[node]);
> > + }
> > +out2:
> > + misc_deregister(&mmtimer_miscdev);
> > +out1:
> > + free_irq(SGI_MMTIMER_VECTOR, NULL);
> > + goto out;
> > +
> > }
> >
> > module_init(mmtimer_init);
> > diff --git a/drivers/char/tpm/tpm.c b/drivers/char/tpm/tpm.c
> > --- a/drivers/char/tpm/tpm.c
> > +++ b/drivers/char/tpm/tpm.c
> > @@ -1155,6 +1155,7 @@ #define DEVNAME_SIZE 7
> >
> > if (sysfs_create_group(&dev->kobj, chip->vendor.attr_group)) {
> > list_del(&chip->list);
> > + misc_deregister(&chip->vendor.miscdev);
> > put_device(dev);
> > clear_bit(chip->dev_num, dev_mask);
> > kfree(chip);
> > diff --git a/drivers/input/misc/hp_sdc_rtc.c b/drivers/input/misc/hp_sdc_rtc.c
> > --- a/drivers/input/misc/hp_sdc_rtc.c
> > +++ b/drivers/input/misc/hp_sdc_rtc.c
> > @@ -693,9 +693,13 @@ static int __init hp_sdc_rtc_init(void)
> >
> > init_MUTEX(&i8042tregs);
> >
> > + INIT_LIST_HEAD(&hp_sdc_rtc_dev.list);
> > +
> > if ((ret = hp_sdc_request_timer_irq(&hp_sdc_rtc_isr)))
> > return ret;
> > - misc_register(&hp_sdc_rtc_dev);
> > + if (misc_register(&hp_sdc_rtc_dev) != 0)
> > + printk(KERN_INFO "Could not register misc. dev for sdc\n");
> > +
> > create_proc_read_entry ("driver/rtc", 0, NULL,
> > hp_sdc_rtc_read_proc, NULL);
> >
> > diff --git a/drivers/macintosh/apm_emu.c b/drivers/macintosh/apm_emu.c
> > --- a/drivers/macintosh/apm_emu.c
> > +++ b/drivers/macintosh/apm_emu.c
> > @@ -520,6 +520,8 @@ static int __init apm_emu_init(void)
> > {
> > struct proc_dir_entry *apm_proc;
> >
> > + INIT_LIST_HEAD(&apm_device.list);
> > +
> > if (sys_ctrler != SYS_CTRLER_PMU) {
> > printk(KERN_INFO "apm_emu: Requires a machine with a PMU.\n");
> > return -ENODEV;
> > @@ -529,7 +531,8 @@ static int __init apm_emu_init(void)
> > if (apm_proc)
> > apm_proc->owner = THIS_MODULE;
> >
> > - misc_register(&apm_device);
> > + if (misc_register(&apm_device) != 0)
> > + printk(KERN_INFO "Could not create misc. device for apm\n");
> >
> > pmu_register_sleep_notifier(&apm_sleep_notifier);
> >
> > diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> > --- a/drivers/net/tun.c
> > +++ b/drivers/net/tun.c
> > @@ -856,6 +856,8 @@ static int __init tun_init(void)
> > printk(KERN_INFO "tun: %s, %s\n", DRV_DESCRIPTION, DRV_VERSION);
> > printk(KERN_INFO "tun: %s\n", DRV_COPYRIGHT);
> >
> > + INIT_LIST_HEAD(&tun_miscdev.list);
> > +
> > ret = misc_register(&tun_miscdev);
> > if (ret)
> > printk(KERN_ERR "tun: Can't register misc device %d\n", TUN_MINOR);
> > diff --git a/fs/dlm/user.c b/fs/dlm/user.c
> > --- a/fs/dlm/user.c
> > +++ b/fs/dlm/user.c
> > @@ -773,6 +773,7 @@ int dlm_user_init(void)
> > ctl_device.name = "dlm-control";
> > ctl_device.fops = &ctl_device_fops;
> > ctl_device.minor = MISC_DYNAMIC_MINOR;
> > + INIT_LIST_HEAD(&ctl_device.list);
> >
> > error = misc_register(&ctl_device);
> > if (error)

--
/***************************************************
*Neil Horman
*Software Engineer
*gpg keyid: 1024D / 0x92A74FA1 - http://pgp.mit.edu
***************************************************/