Re: [PATCH 4.4 16/30] [media] pvrusb2: reduce stack usage pvr2_eeprom_analyze()
From: Greg Kroah-Hartman
Date: Mon Jul 03 2017 - 03:31:58 EST
On Thu, Jun 29, 2017 at 05:15:17PM +0100, Ben Hutchings wrote:
> On Mon, 2017-06-19 at 23:20 +0800, Greg Kroah-Hartman wrote:
> > 4.4-stable review patch. If anyone has any objections, please let me know.
> > ------------------
> > From: Arnd Bergmann <arnd@xxxxxxxx>
> > commit 6830733d53a4517588e56227b9c8538633f0c496 upstream.
> > The driver uses a relatively large data structure on the stack, which
> > showed up on my radar as we get a warning with the "latent entropy"
> > GCC plugin:
> > drivers/media/usb/pvrusb2/pvrusb2-eeprom.c:153:1: error: the frame size of 1376 bytes is larger than 1152 bytes [-Werror=frame-larger-than=]
> > The warning is usually hidden as we raise the warning limit to 2048
> > when the plugin is enabled, but I'd like to lower that again in the
> > future, and making this function smaller helps to do that without
> > build regressions.
> > Further analysis shows that putting an 'i2c_client' structure on
> > the stack is not really supported, as the embedded 'struct device'
> > is not initialized here, and we are only saved by the fact that
> > the function that is called here does not use the pointer at all.
> That is not true in 4.4-stable. This commit depends on:
> commit 6037b3ca28f4258d913dbe77248fd77827702ae3
> Author: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
> Date: Wed Nov 16 14:21:48 2016 -0200
> [media] tveeprom: print log messages using pr_foo()
It does? I don't understand how the two are connected. Removing
i2c_client off of the stack is a good thing. Ah, I see how the pointer
is used in tveeprom_hauppauge_analog(), but this shouldn't matter here,