On Tuesday 13 February 2007, Arjan van de Ven wrote: > Hi, > > while working on the last pieces of the file_ops constantification, DVB > is the small village in France that is holding the Romans at bay... but > I think I found the final flaw in it now: > > *pdvbdev = dvbdev = kmalloc(sizeof(struct dvb_device), GFP_KERNEL); > > if (!dvbdev) { > mutex_unlock(&dvbdev_register_lock); > return -ENOMEM; > } > > memcpy(dvbdev, template, sizeof(struct dvb_device)); > dvbdev->type = type; > dvbdev->id = id; > dvbdev->adapter = adap; > dvbdev->priv = priv; > > dvbdev->fops->owner = adap->module; > > > this is the place in DVB that is writing to a struct file_operations. > But as with almost all such cases in the kernel, this one is buggy: > While the code nicely copies a template dvbdev, that template only has a > pointer to a *shared* fops struct, the copy doesn't help that. So this > code is overwriting the fops owner field for ALL active devices, not > just the ones the copy of the template is for.... > > I'm lost in the maze of this part of DVB (it seems to have some magic > potion to resist me) but I was hoping some of the local citizens could > take a look at this buglet... > > Greetings, > Arjan van de Ven
hi arjan, thanks for pointing out this issue. attached find a patch that fixes the problem. @mauro - please pull changeset a7ac92d208fe dvbdev: fix illegal re-usage of fileoperations struct from http://www.linuxtv.org/hg/~mws/v4l-dvb-fixtree for upstream to kernel. thanks. best regards marcel
diff -r 667e84e2e762 linux/drivers/media/dvb/dvb-core/dvbdev.c --- a/linux/drivers/media/dvb/dvb-core/dvbdev.c Tue Feb 13 07:00:55 2007 -0200 +++ b/linux/drivers/media/dvb/dvb-core/dvbdev.c Tue Feb 13 12:00:13 2007 +0100 @@ -211,12 +211,14 @@ int dvb_register_device(struct dvb_adapt const struct dvb_device *template, void *priv, int type) { struct dvb_device *dvbdev; + struct file_operations *dvbdevfops; + int id; if (mutex_lock_interruptible(&dvbdev_register_lock)) return -ERESTARTSYS; - if ((id = dvbdev_get_free_id (adap, type)) < 0) { + if ((id = dvbdev_get_free_id (adap, type)) < 0){ mutex_unlock(&dvbdev_register_lock); *pdvbdev = NULL; printk ("%s: could get find free device id...\n", __FUNCTION__); @@ -225,7 +227,15 @@ int dvb_register_device(struct dvb_adapt *pdvbdev = dvbdev = kmalloc(sizeof(struct dvb_device), GFP_KERNEL); - if (!dvbdev) { + if (!dvbdev){ + mutex_unlock(&dvbdev_register_lock); + return -ENOMEM; + } + + dvbdevfops = kzalloc(sizeof(struct file_operations), GFP_KERNEL); + + if (!dvbdevfops){ + kfree (dvbdev); mutex_unlock(&dvbdev_register_lock); return -ENOMEM; } @@ -235,7 +245,7 @@ int dvb_register_device(struct dvb_adapt dvbdev->id = id; dvbdev->adapter = adap; dvbdev->priv = priv; - + dvbdev->fops = dvbdevfops; dvbdev->fops->owner = adap->module; list_add_tail (&dvbdev->list_head, &adap->device_list); @@ -263,6 +273,7 @@ void dvb_unregister_device(struct dvb_de dvbdev->type, dvbdev->id))); list_del (&dvbdev->list_head); + kfree (dvbdev->fops); kfree (dvbdev); } EXPORT_SYMBOL(dvb_unregister_device);
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