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

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Date:	Wed, 30 Dec 2015 21:24:21 +0800
From:	Bamvor Jian Zhang <bamvor.zhangjian@...aro.org>
To:	Sudip Mukherjee <sudipm.mukherjee@...il.com>,
	Arnd Bergmann <arnd@...db.de>
Cc:	linux-kernel@...r.kernel.org, y2038@...ts.linaro.org,
	gregkh@...uxfoundation.org, broonie@...nel.org,
	Bamvor Zhang Jian <bamvor.zhangjian@...aro.org>
Subject: Re: [PATCH v2 2/2] ppdev: add support for compat ioctl

Hi, Sudip

On 12/30/2015 07:16 PM, Sudip Mukherjee wrote:
> 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)
Thanks for your testing. It seems that I misuse the parameters. Could
you please apply the following patch and try it again?
There is no parport in my computer, Thanks.

diff --git a/drivers/char/ppdev.c b/drivers/char/ppdev.c
index 31bc7b7..9e98d01 100644
--- a/drivers/char/ppdev.c
+++ b/drivers/char/ppdev.c
@@ -636,7 +636,7 @@ static int pp_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		if ((time32[0] < 0) || (time32[1] < 0))
 			return -EINVAL;
 
-		if (copy_to_user(time32, argp, sizeof(time32)))
+		if (copy_to_user(argp, time32, sizeof(time32)))
 			return -EFAULT;
 
 		return 0;
@@ -648,7 +648,7 @@ static int pp_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 		if ((time64[0] < 0) || (time64[1] < 0))
 			return -EINVAL;
 
-		if (copy_to_user(time64, argp, sizeof(time64)))
+		if (copy_to_user(argp, time64, sizeof(time64)))
 			return -EFAULT;
 
 		return 0;

Regards

Bamvor

> 
> regards
> sudip
> 
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