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Date: Mon, 02 Mar 2015 14:02:56 +0100 From: Alexander Holler <holler@...oftware.de> To: Al Viro <viro@...IV.linux.org.uk>, Richard Weinberger <richard.weinberger@...il.com> CC: USB list <linux-usb@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org> Subject: Re: gadgetfs broken since 7f7f25e8 Am 02.03.2015 um 12:39 schrieb Alexander Holler: > Am 02.03.2015 um 11:20 schrieb Al Viro: >> On Mon, Mar 02, 2015 at 10:13:27AM +0100, Richard Weinberger wrote: >>> On Mon, Mar 2, 2015 at 9:28 AM, Alexander Holler >>> <holler@...oftware.de> wrote: >>>> Hello. >>>> >>>> Commit 7f7f25e82d54870df24d415a7007fbd327da027b (introduced with >>>> 3.16) broke >>>> dynamic changing of file_operations->[read|write]. >>>> >>>> At least gadgetfs is a victim. >>>> >>>> Feel free to ask me off-list for a patch as I don't want to end up in >>>> annoying discussions on Linux kernel lists anymore. >>>> >>>> Alexander Holler >>> >>> CC'ing Al. >> >> I know. FWIW, gadgetfs is one of the very few places that tried to >> pull that >> crap off and it had always been seriously racy. I've posted a partial >> analysis >> about a month ago (<20150204190645.GJ29656@...IV.linux.org.uk>). >> >> If Alexander (or anybody else) has a patch that really fixes that thing, >> I would certainly like to see it. If not, I'll try to cook something, >> but I'm not very familiar with that code. I really hope that this patch >> isn't "modify ->f_mode to match ->f_op change" - that's too racy. >> We'll obviously need to fix the userland-visible breakage in that one, >> but that's not the way to go... > > I exactly did what you've assumed, I've just fixed f_mode but not the > already existing races which I haven't introduced. So I was right in not > sending a patch as would have been blamed for not rewriting everything > as so often. Another quick solution would be to just add some dummy ops for read/write to those file_operations which are missing it which are only returning -EINVAL or some other error which might make sense. But that still won't fix any existing race occuring while changing the the ops. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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