Messages in this thread Patch in this message | | | Date | Thu, 08 Nov 2007 18:53:40 +0800 | From | Miao Xie <> | Subject | [PATCH] time: fix sysfs_show_{available,current}_clocksources() buffer overflow problem |
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Hi,every one. 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>
--- kernel/time/clocksource.c | 19 ++++++++++--------- 1 files changed, 10 insertions(+), 9 deletions(-)
diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index c8a9d13..5d5926f 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -342,15 +342,13 @@ void clocksource_change_rating(struct clocksource *cs, int rating) 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; }
/** @@ -418,17 +416,20 @@ 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; }
/* -- 1.5.3
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