Re: linux-next: build warning after merge of the suspend tree

[Rafael J. Wysocki]

On Tuesday, May 24, 2011, mark gross wrote:
> On Mon, May 23, 2011 at 09:54:52PM +0200, Rafael J. Wysocki wrote:
> > On Monday, May 23, 2011, mark gross wrote:
> > > On Mon, May 23, 2011 at 03:06:36PM +1000, Stephen Rothwell wrote:
> > > > Hi Rafael,
> > > > 
> > > > After merging the suspend tree, today's linux-next build (i386 defconfig
> > > > among others) produced this warning:
> > > > 
> > > > kernel/pm_qos_params.c: In function 'pm_qos_power_write':
> > > > kernel/pm_qos_params.c:420: warning: passing argument 3 of 'kstrtol' from incompatible pointer type
> > > > include/linux/kernel.h:210: note: expected 'long int *' but argument is of type 's32 *'
> > > > 
> > > > Intreoduced by commit 365daa955e03 ("PM: Correct PM QOS's user mode
> > > > interface to work with ascii input per").
> > > 
> > > Gah!  I'm sorry about that.
> > > 
> > > attached is a fix.
> > > 
> > > 
> > > --mark
> > > 
> > > signed-off-by:markgross <markgross@xxxxxxxxxxx>
> > > 
> > > 
> > > 
> > > From a8f0587b9ae598be5ca4c3cdda4e0ced6ca9baaf Mon Sep 17 00:00:00 2001
> > > From: mgross <mgross@cr48>
> > > Date: Mon, 23 May 2011 07:14:09 -0700
> > > Subject: [PATCH] clean up a compile time warning in the use of strict_strtol but that was
> > >  passing an s32 * when it should be passing a long *
> > > 
> > > ---
> > >  kernel/pm_qos_params.c |    6 ++++--
> > >  1 files changed, 4 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/kernel/pm_qos_params.c b/kernel/pm_qos_params.c
> > > index d61ecf3..dd37c56 100644
> > > --- a/kernel/pm_qos_params.c
> > > +++ b/kernel/pm_qos_params.c
> > > @@ -405,6 +405,7 @@ static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
> > >  		size_t count, loff_t *f_pos)
> > >  {
> > >  	s32 value;
> > > +	long safe_int;
> > >  	int x;
> > >  	char ascii_value[11];
> > >  	struct pm_qos_request_list *pm_qos_req;
> > > @@ -417,10 +418,11 @@ static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
> > >  		ascii_value[count] = 0;
> > >  		if (copy_from_user(ascii_value, buf, count))
> > >  			return -EFAULT;
> > > -		if ((x=strict_strtol(ascii_value, 16, &value)) != 0){
> > > -			pr_debug("%s, 0x%x, 0x%x\n",ascii_value, value, x);
> > > +		if ((x=strict_strtol(ascii_value, 16, &safe_int)) != 0){
> > > +			pr_debug("%s, 0x%lx, 0x%x\n",ascii_value, safe_int, x);
> > >  			return -EINVAL;
> > >  		}
> > > +		value = (s32) safe_int;
> > 
> > Well, this doesn't seem quite right.
> > 
> > >  	} else
> > >  		return -EINVAL;
> > 
> > Besides, if count == 11, there we'll write beyond ascii_value[], right?
> 
> right. That is a bug.
> 
> > 
> > What about the appended patch instead of your original one?
> Thank you!
> 
> > Rafael
> > 
> > 
> > ---
> > From: mark gross <markgross@xxxxxxxxxxx>
> > Subject: PM: Correct PM QOS's user mode interface to work with ascii input per
> > 
> > What is in the kernel docs.  Writing a string to the ABI from user mode
> > comes in 2 flavors.  One with and one without a '\n' at the end.  This
> > change accepts both.
> > 
> > # echo 0x12345678 > /dev/cpu_dma_latency
> > 
> > and
> > 
> > # echo -n 0x12345678 > /dev/cpu_dma_latency
> > 
> > now both work.
> > 
> > [rjw: Fixed up array bounds checking and type casting.]
> > 
> > Signed-off-by: mark gross <markgross@xxxxxxxxxxx>
> > Acked-by: Simon Horman <horms@xxxxxxxxxxxx>
> > Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
> > ---
> >  kernel/pm_qos_params.c |   25 ++++++++++++++++---------
> >  1 file changed, 16 insertions(+), 9 deletions(-)
> > 
> > Index: linux-2.6/kernel/pm_qos_params.c
> > ===================================================================
> > --- linux-2.6.orig/kernel/pm_qos_params.c
> > +++ linux-2.6/kernel/pm_qos_params.c
> > @@ -40,6 +40,7 @@
> >  #include <linux/string.h>
> >  #include <linux/platform_device.h>
> >  #include <linux/init.h>
> > +#include <linux/kernel.h>
> >  
> >  #include <linux/uaccess.h>
> >  
> > @@ -404,24 +405,30 @@ static ssize_t pm_qos_power_write(struct
> >  		size_t count, loff_t *f_pos)
> >  {
> >  	s32 value;
> > -	int x;
> >  	char ascii_value[11];
> >  	struct pm_qos_request_list *pm_qos_req;
> >  
> >  	if (count == sizeof(s32)) {
> >  		if (copy_from_user(&value, buf, sizeof(s32)))
> >  			return -EFAULT;
> > -	} else if (count == 11) { /* len('0x12345678/0') */
> > -		if (copy_from_user(ascii_value, buf, 11))
> > +	} else if (count >= 10) { /* '0x12345678' or '0x12345678\n'*/
> Did you mean <= 11 here?  I know that Alan Stern wanted to see the ABI
> adjusted to accept shorter hex string that the full 10 char string.
> 
> FWIW I'm ok with doing that.
> 
> > +		unsigned long int ulval;
> > +		int ret;
> > +
> > +		count = 10;
> 
> I kind of wanted to return an error to the user if they violate the
> documented format for the hex string.  With this code you get a silent
> truncation of the lower digits if the string is "0x123456789abcdef"

That's correct, but with the previous code there will be a truncation
is "echo -n 0x123456789".  If we don't want that, we should check if the
last character is a '\n'.

> > +		ascii_value[count] = 0;
> > +		if (copy_from_user(ascii_value, buf, count))
> >  			return -EFAULT;
> > -		if (strlen(ascii_value) != 10)
> > -			return -EINVAL;
> > -		x = sscanf(ascii_value, "%x", &value);
> > -		if (x != 1)
> > +
> > +		ret = strict_strtoul(ascii_value, 16, &ulval);
> > +		if (ret){
> > +			pr_debug("%s, 0x%lx, 0x%x\n", ascii_value, ulval, ret);
> >  			return -EINVAL;
> > -		pr_debug("%s, %d, 0x%x\n", ascii_value, x, value);
> > -	} else
> > +		}
> > +		value = (s32)lower_32_bits(ulval);
> This shouldn't be needed if you are constrained to a hex format of
> "0x12345678" but this is more readable.  lower_32_bits is a good idea.

OK

Appended is another patch that adds the '\n' check and reworks the code
a bit (so that it will accept strings like "0x1" too).

Thanks,
Rafael


---
From: Rafael J. Wysocki <rjw@xxxxxxx>
Subject: PM: Fix PM QOS's user mode interface to work with ASCII input

Make pm_qos_power_write() accept values passed to it in the ASCII hex
format either with or without an ending newline.

Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
---
 kernel/pm_qos_params.c |   33 +++++++++++++++++++++++----------
 1 file changed, 23 insertions(+), 10 deletions(-)

Index: linux-2.6/kernel/pm_qos_params.c
===================================================================
--- linux-2.6.orig/kernel/pm_qos_params.c
+++ linux-2.6/kernel/pm_qos_params.c
@@ -40,6 +40,7 @@
 #include <linux/string.h>
 #include <linux/platform_device.h>
 #include <linux/init.h>
+#include <linux/kernel.h>
 
 #include <linux/uaccess.h>
 
@@ -404,24 +405,36 @@ static ssize_t pm_qos_power_write(struct
 		size_t count, loff_t *f_pos)
 {
 	s32 value;
-	int x;
-	char ascii_value[11];
 	struct pm_qos_request_list *pm_qos_req;
 
 	if (count == sizeof(s32)) {
 		if (copy_from_user(&value, buf, sizeof(s32)))
 			return -EFAULT;
-	} else if (count == 11) { /* len('0x12345678/0') */
-		if (copy_from_user(ascii_value, buf, 11))
+	} else if (count <= 11) { /* ASCII perhaps? */
+		char ascii_value[11];
+		unsigned long int ulval;
+		int ret;
+
+		if (copy_from_user(ascii_value, buf, count))
 			return -EFAULT;
-		if (strlen(ascii_value) != 10)
-			return -EINVAL;
-		x = sscanf(ascii_value, "%x", &value);
-		if (x != 1)
+
+		if (count > 10) {
+			if (ascii_value[10] == '\n')
+				ascii_value[10] = '\0';
+			else
+				return -EINVAL;
+		} else {
+			ascii_value[count] = '\0';
+		}
+		ret = strict_strtoul(ascii_value, 16, &ulval);
+		if (ret) {
+			pr_debug("%s, 0x%lx, 0x%x\n", ascii_value, ulval, ret);
 			return -EINVAL;
-		pr_debug("%s, %d, 0x%x\n", ascii_value, x, value);
-	} else
+		}
+		value = (s32)lower_32_bits(ulval);
+	} else {
 		return -EINVAL;
+	}
 
 	pm_qos_req = filp->private_data;
 	pm_qos_update_request(pm_qos_req, value);
--
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