Messages in this thread | | | Subject | Re: [PATCH] LinuxPPS - PPS support for Linux | From | Roland Dreier <> | Date | Tue, 23 Oct 2007 14:08:19 -0700 |
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A few comments:
> + dev_err(port->dev, "PPS support disabled due port \"%s\" is " > + "in polling mode\n",
I think "because" instead of "due" is closer to standard English.
> + printk(KERN_ERR "pps: %s: too much PPS sources in the system\n", > + info->name);
Similarly should be "many" instead of "much".
> + /* Get new ID for the new PPS source */ > + if (idr_pre_get(&pps_idr, GFP_KERNEL) == 0) { > + err = -ENOMEM; > + goto kfree_pps; > + } > + > + spin_lock_irq(&idr_lock); > + err = idr_get_new(&pps_idr, pps, &id); > + spin_unlock_irq(&idr_lock); > + > + if (err < 0) > + goto kfree_pps;
You usually can handle idr_get_new() returning -EAGAIN by jumping back to the idr_pre_get(), to handle someone else coming in and stealing the memory you just preallocated. In this case it may not matter since it's pretty unlikely that a lot of contexts are using the idr at the same time. But anyway...
> +void pps_unregister_source(int source) > ... > + wait_event(pps->usage_queue, atomic_read(&pps->usage) == 0); > + > + pps_sysfs_remove_source_entry(pps); > + pps_unregister_cdev(pps); > + kfree(pps);
This reference counting looks dubious to me... later on in the code you have:
> +static int pps_cdev_open(struct inode *inode, struct file *file) > +{ > + struct pps_device *pps = container_of(inode->i_cdev, > + struct pps_device, cdev); > + > + /* Lock the PPS source against (possible) deregistration */ > + atomic_inc(&pps->usage);
with no locking, so I see no reason why the atomic_inc() couldn't happen right after the wait_event() sees a count of 0 and lets the deregistration continue. Which would lead to use-after-free.
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