linux-kernel - Re: [PATCH] PCI: endpoint: pci-epf-test: Move DMA check into read/write/copy functions

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAAEEuhp2Cm3ujGB_C3Z7XwQh1whP9BcdT+WOT3w+sa-CK9p3fA@mail.gmail.com>
Date: Fri, 9 Aug 2024 08:56:29 +0200
From: Rick Wertenbroek <rick.wertenbroek@...il.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: rick.wertenbroek@...g-vd.ch, dlemoal@...nel.org, 
	alberto.dassatti@...g-vd.ch, 
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, Krzysztof Wilczyński <kw@...ux.com>, 
	Kishon Vijay Abraham I <kishon@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Niklas Cassel <cassel@...nel.org>, Frank Li <Frank.Li@....com>, 
	Lars-Peter Clausen <lars@...afoo.de>, linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: endpoint: pci-epf-test: Move DMA check into
 read/write/copy functions

On Tue, Aug 6, 2024 at 9:15 PM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> On Tue, Aug 06, 2024 at 06:27:54PM +0200, Rick Wertenbroek wrote:
> > The test for a DMA transfer was done in pci_epf_test_cmd_handler, which
> > if not supported would lead to the endpoint function just printing an
> > error message and waiting for further commands. This would leave the
>
> I guess it's the *test* that prints the error message?  Is this the
> "Cannot transfer data using DMA" message?

That is the error message, the error message is printed by the
endpoint function, on the endpoint device. On the host side, nothing
happens; the test program just hangs because the driver waits
indefinitely. With the change I proposed, the test program completes
the test and will display "NOT OKAY" as normal when a test fails.

>
> > host side PCI driver waiting for an interrupt because the call to
> > pci_epf_test_raise_irq is skipped. The host side driver
> > drivers/misc/pci_endpoint_test.c would hang indefinitely when sending
> > a transfer request with DMA if the endpoint does not support it.
> > This is because wait_for_completion() is used in the host side driver.
> >
> > Move the DMA check into the read/write/copy functions so that they
> > report a transfer (IO) error so that pci_epf_test_raise_irq() is
> > called when a transfer with DMA is requested, even if unsupported.
>
> Add "()" after function names above, as you did for
> pci_epf_test_raise_irq().

I will add this.

>
> > The host side driver will still report an error on transfer thanks
> > to the checksum, because no data was moved, but will not hang anymore
> > waiting for an interrupt that will never arrive.

Thanks.
Regards,
Rick