Messages in this thread | | | Date | Sat, 21 Oct 2017 09:51:46 +0200 | From | Greg KH <> | Subject | Re: [PATCH] genwqe: Take R/W permissions into account when dealing with memory pages |
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On Fri, Oct 20, 2017 at 05:27:49PM -0200, Guilherme G. Piccoli wrote: > Currently we assume userspace pages are always writable when doing > memory pinning. This is not true, specially since userspace applications > may allocate their memory the way they want, we have no control over it. > If a read-only page is set for pinning, currently the driver fails due > to get_user_pages_fast() refusing to map read-only pages as writable. > > This patch changes this behavior, by taking the permission flags of the > pages into account in both pinning/unpinning process, as well as in the > DMA data copy-back to userpace (which we shouldn't try to do blindly, > since it will fail in case of read-only-pages). > > Signed-off-by: Frank Haverkamp <haver@linux.vnet.ibm.com> > Signed-off-by: Guilherme G. Piccoli <gpiccoli@linux.vnet.ibm.com> > --- > > Arnd/Greg, we found this bug recently, although not critical, > it's really a boring issue affecting driver functionality. > If it's possible to take this patch still on v4.14, we'd be > really thankful! > But we know it's late, so if not possible, v4.15 is cool.
Is this a regression? It seems like it's just a "fix something that has always been broken but no one has noticed yet" type of thing, right?
thanks,
greg k-h
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