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time: fix sysfs_show_{available,current}_clocksources() buffer overflow problem 

I found that there is a buffer overflow problem in the following code.

Version:	2.6.24-rc2,
File:		kernel/time/clocksource.c:417-432
--------------------------------------------------------------------
static ssize_t
sysfs_show_available_clocksources(struct sys_device *dev, char *buf)
{
	struct clocksource *src;
	char *curr = buf;

	spin_lock_irq(&clocksource_lock);
	list_for_each_entry(src, &clocksource_list, list) {
		curr += sprintf(curr, "%s ", src->name);
	}
	spin_unlock_irq(&clocksource_lock);

	curr += sprintf(curr, "\n");

	return curr - buf;
}
-----------------------------------------------------------------------

sysfs_show_current_clocksources() also has the same problem though in practice
the size of current clocksource's name won't exceed PAGE_SIZE.

I fix the bug by using snprintf according to the specification of the kernel
(Version:2.6.24-rc2,File:Documentation/filesystems/sysfs.txt)

Fix sysfs_show_available_clocksources() and sysfs_show_current_clocksources()
buffer overflow problem with snprintf().

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Cc: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Miao Xie 2008-02-06 01:36:53 -08:00 committed by Linus Torvalds
parent be6c28e62e
commit 5e2cb1018a
1 changed files with 10 additions and 9 deletions
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19
kernel/time/clocksource.c
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@ -363,15 +363,13 @@ void clocksource_unregister(struct clocksource *cs)
static ssize_t
sysfs_show_current_clocksources(struct sys_device *dev, char *buf)
{
char *curr = buf;
ssize_t count = 0;
spin_lock_irq(&clocksource_lock);
curr += sprintf(curr, "%s ", curr_clocksource->name);
count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
spin_unlock_irq(&clocksource_lock);
curr += sprintf(curr, "\n");
return curr - buf;
return count;
}
/**
@ -439,17 +437,20 @@ static ssize_t
sysfs_show_available_clocksources(struct sys_device *dev, char *buf)
{
struct clocksource *src;
char *curr = buf;
ssize_t count = 0;
spin_lock_irq(&clocksource_lock);
list_for_each_entry(src, &clocksource_list, list) {
curr += sprintf(curr, "%s ", src->name);
count += snprintf(buf + count,
max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
"%s ", src->name);
}
spin_unlock_irq(&clocksource_lock);
curr += sprintf(curr, "\n");
count += snprintf(buf + count,
max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
return curr - buf;
return count;
}
/*