linux-kernel - Re: [PATCH v2 2/2] ppdev: add support for compat ioctl

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Message-ID: <20151230111648.GA29697@sudip-pc>
Date:	Wed, 30 Dec 2015 16:46:48 +0530
From:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Bamvor Jian Zhang <bamvor.zhangjian@...aro.org>,
	linux-kernel@...r.kernel.org, y2038@...ts.linaro.org,
	gregkh@...uxfoundation.org, broonie@...nel.org
Subject: Re: [PATCH v2 2/2] ppdev: add support for compat ioctl

On Fri, Dec 18, 2015 at 12:12:05AM +0100, Arnd Bergmann wrote:
> On Thursday 17 December 2015 17:58:52 Bamvor Jian Zhang wrote:
> > The arg of ioctl in ppdev is the pointer of integer except the
> > timeval in PPSETTIME, PPGETTIME. Different size of timeval
> > is already supported by the previous patches. So, it is safe
> > to add compat support.
> > 
> > Signed-off-by: Bamvor Jian Zhang <bamvor.zhangjian@...aro.org>
> > 
> 
> Reviewed-by: Arnd Bergmann <arnd@...db.de>
> 
> (I think I replied with the reviewed-by tag before to this patch)

I was testing this series today. And it is breaking my userspace code. I
am attaching my userspace code for you to check. Its very simple
userspace code:
1: open
2: ioctl to claim
3: ioctl - PPGETTIME
4: ioctl - PPSETTIME
5: ioctl - PPGETTIME
6: ioctl - release
7: close

Without this series it works as expected.

With this series applied, the userspace code prints the error message:
PPNEGOT: Bad address

I traced it with strace and:
ioctl(3, PPGETTIME, 0xbfe91508)         = -1 EFAULT (Bad address)

regards
sudip

View attachment "ppdev_user.c" of type "text/x-csrc" (891 bytes)