Messages in this thread Patch in this message | | | Date | Tue, 10 Jan 2012 11:18:13 +0100 (CET) | From | Sebastian Ott <> | Subject | Re: Incorrect uses of get_driver()/put_driver() |
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On Tue, 10 Jan 2012, Dmitry Torokhov wrote: > On Tue, Jan 10, 2012 at 10:05:41AM +0100, Martin Schwidefsky wrote: > > On Mon, 9 Jan 2012 12:35:09 -0500 (EST) > > Alan Stern <stern@rowland.harvard.edu> wrote: > > > > > drivers/s390/cio/device.c:1681: drv = get_driver(&cdrv->driver); > > > drivers/s390/cio/device.c:1687: put_driver(drv); > > > > > > Martin, these calls seem to be useless. The calls in ccwgroup.c are > > > definitely useless; there's no reason to take a reference to a driver > > > while it's being unregistered, since it can't go away until the > > > unregistration is finished. > > > > The get_driver/put_driver in ccwgroup.c are obviously useless, the caller > > passed ccwgroup_driver_unregister a ccwgroup_driver reference. > > I am not so sure about the code in device.c. get_ccwdev_by_busid() gets > > used e.g. by vmur like this: > > It does not matter how it is being used. Either get_ccwdev_by_busid() > gets a valid driver structure or you already lost. You can not say that > get_driver() protects anything, since if there is a chance driver can > disappear it can disappear before we get to executing get_driver() code. > > So while you might want to audit callers get/put_driver inside of > get_ccwdev_by_busid() is utterly useless.
Yes, the caller has to ensure valid driver pointers. We have one offender here:
[PATCH] zfcp: fops add owner
Set the owner member of zfcp_cfdc_fops, to ensure that the caller of these functions holds a module reference.
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com> --- drivers/s390/scsi/zfcp_cfdc.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/drivers/s390/scsi/zfcp_cfdc.c +++ b/drivers/s390/scsi/zfcp_cfdc.c @@ -13,6 +13,7 @@ #include <linux/slab.h> #include <linux/types.h> +#include <linux/module.h> #include <linux/miscdevice.h> #include <asm/compat.h> #include <asm/ccwdev.h> @@ -249,6 +250,7 @@ static long zfcp_cfdc_dev_ioctl(struct f } static const struct file_operations zfcp_cfdc_fops = { + .owner = THIS_MODULE, .open = nonseekable_open, .unlocked_ioctl = zfcp_cfdc_dev_ioctl, #ifdef CONFIG_COMPAT
> > Thanks. > > -- > Dmitry > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > >
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