On Thu, Feb 24, 2011 at 12:00:35PM -0500, Alan Stern wrote:
> On Thu, 24 Feb 2011, mark gross wrote:
>
> > > How careful do you want to be here? For example, which of the
> > > following inputs do you want to accept?
> > >
> > > 0x1234
> > > abcd1234
> > > abcd123456
> > > abcd123456\n
> > > abcd1234567
> > > 1234567890
> > > 1234567890\n
> > > 12345678901
> >
> > > 0x12345678
> > > 0x12345678\n
> > just these 2 are what I had planned to allow after this email thread.
> >
> > > 0x123456789
> > >
> > > Maybe it's okay to be a little relaxed about this, and trust the caller
> > > to pass in data that makes sense.
> > yeah but is it worth the effort?
>
> Checking for exactly those two forms really is a lot of effort. You
> have to make sure the first two characters are "0x" or "0X", you have
> to check that each of the next eight characters is a valid hex digit,
> and you have to verify that the 11th character, if present, is a
> newline.
>
> If you can get results that are good enough just by calling
> strict_strtoul() without all these checks, it's probably worthwhile.
>
I just don't want any buffer overrun bugs in code I'm writing.
I like the attached thank you for all the really useful input.
--mark
Signed-off-by: mark gross <markgross@xxxxxxxxxxx>
>From df199e491c750c529abcfb0e2256f508f1afd061 Mon Sep 17 00:00:00 2001
From: mark gross <markgross@xxxxxxxxxxx>
Date: Sun, 6 Mar 2011 05:45:44 -0800
Subject: [PATCH] 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.
---
kernel/pm_qos_params.c | 15 ++++++++-------
1 files changed, 8 insertions(+), 7 deletions(-)
diff --git a/kernel/pm_qos_params.c b/kernel/pm_qos_params.c
index aeaa7f8..b315446 100644
--- a/kernel/pm_qos_params.c
+++ b/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>
@@ -387,15 +388,15 @@ static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
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 || count == 11) { /* '0x12345678' or
+ '0x12345678/n'*/
+ ascii_value[count] = 0;
+ if (copy_from_user(ascii_value, buf, count))
return -EFAULT;
- if (strlen(ascii_value) != 10)
+ if ((x=strict_strtol(ascii_value, 16, &value)) != 0){
+ pr_debug("%s, 0x%x, 0x%x\n",ascii_value, value, x);
return -EINVAL;
- x = sscanf(ascii_value, "%x", &value);
- if (x != 1)
- return -EINVAL;
- pr_debug("%s, %d, 0x%x\n", ascii_value, x, value);
+ }
} else
return -EINVAL;
--
1.7.1
_______________________________________________
linux-pm mailing list
linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linux-foundation.org/mailman/listinfo/linux-pm
