Messages in this thread | ![/](/images/icornerl.gif) | | From | Arnd Bergmann <> | Subject | Re: ioctl32_unregister_conversion & modules | Date | Fri, 09 May 2003 14:10:31 +0200 |
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Pavel Machek wrote:
> ...what is the problem? > > It seems that function pointers into modules do not need any special > treatmeant [I *know* there was talk about this on l-k; but I can't > find anything in Documentation/]: > > if (!capable(CAP_SYS_ADMIN)) > return -EACCES; > if (disk->fops->ioctl) { > ret = disk->fops->ioctl(inode, file, cmd, arg); > if (ret != -EINVAL) > return ret; > }
This is protected against unload by the reference counting done in open()/release(). ->ioctl() can be called only for open devices, so you know the ioctl handler is not getting unloaded while it is running.
> So... what's the problem with {un}register_ioctl32_conversion being > called from module_init/module_exit? Drivers in the tree do it > already...
The problem is that when the conversion handler is called, the reference counting is only done for the module listed as ->owner in the file operations. For example in the patch you submitted to add register_ioctl32_conversion() to drivers/serial/core.c I see nothing stopping you from unloading core.ko while the handler is running on a device owned by drivers/char/cyclades.c or any other serial driver. It does not even have to be run on a serial driver, a user might try to do ioctl(TIOCGSERIAL, ...) on a regular file...
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