From: Christoph Hellwig <hch@lst.de>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Christoph Hellwig <hch@lst.de>,
linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
Hillf Danton <hdanton@sina.com>,
Thomas Gleixner <tglx@linutronix.de>,
Jeremy Linton <jeremy.linton@arm.com>,
syzbot+353be47c9ce21b68b7ed@syzkaller.appspotmail.com,
stable <stable@vger.kernel.org>
Subject: Re: [PATCH] USB: usbfs: fix mmap dma mismatch
Date: Thu, 14 May 2020 16:39:13 +0200 [thread overview]
Message-ID: <20200514143913.GA27798@lst.de> (raw)
In-Reply-To: <20200514120944.GA2005274@kroah.com>
On Thu, May 14, 2020 at 02:09:44PM +0200, Greg Kroah-Hartman wrote:
> > > + if (dma_mmap_coherent(hcd->self.sysdev, vma, mem, dma_handle,
> > > + size)) {
> > > + dec_usb_memory_use_count(usbm, &usbm->vma_use_count);
> > > + return -EAGAIN;
> > > + }
> >
> > What about a goto label to share the error handling path?
>
> I thought about that, but that's a bit messier than the duplicated lines
> here :)
Actually the error handling looks weird, we can just use normal unwinding
here with an extra call to usb_free_coherent. Also -EAGAIN is a strange
error to return in this case, as it is simply incorrect. I think passing
through the errors from dma_mmap_coherent and remap_pfn_range would make
a lot more sense.
Last but not least I wonder if this is the right place to open code
the localmem and has_dma checks - from a layering POV it should be
a usb_mmap_coherent helper at the same level as usb_alloc_coherent.
prev parent reply other threads:[~2020-05-14 14:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-14 11:27 [PATCH] USB: usbfs: fix mmap dma mismatch Greg Kroah-Hartman
2020-05-14 11:37 ` Jeremy Linton
2020-05-14 11:58 ` Christoph Hellwig
2020-05-14 12:09 ` Greg Kroah-Hartman
2020-05-14 14:39 ` Christoph Hellwig [this message]
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