On Mon, Apr 01, 2013 at 10:21:42PM +0100, Al Viro wrote: > On Mon, Apr 01, 2013 at 02:00:29PM -0700, Greg Kroah-Hartman wrote: > > > > IOW, how do we deal with a race between attempt to open a debugfs file and > > > its removal on driver unload? Greg? > > > > Hm, I thought the i_fop->owner thing would be the needed protection, but > > It will be, if you manage to fetch it...
I agree. > > I guess you are right, it will not. I guess we need to do what > > character devices do and have an "intermediate" fops in order to protect > > this. Would that work? > > You mean, with reassigning ->f_op in ->open()? That'll work, as long as > we have exclusion between removal and fetching the sucker in primary > ->open()... Where would you prefer to stash fops? Ick, that's not going to work as the current api just uses a fops and debugfs doesn't keep anything else hanging around that referes to something "before" that, like 'struct cdev' does. And, it's even worse, look at the use of DEFINE_SIMPLE_ATTRIBUTE(), those take a pointer from a random module to read/write from, and use the fops for the debugfs module. Hopefully no other user of that macro has the same problem, and at first glance, I think that's true, but I might be wrong... Am I allowed to "punt" and say, "removing a module that uses debugfs is not recommended?" :) greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
