The patch titled
time: fix sysfs_show_{available,current}_clocksources() buffer overflow problem
has been added to the -mm tree. Its filename is
time-fix-sysfs_show_availablecurrent_clocksources-buffer-overflow-problem.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: time: fix sysfs_show_{available,current}_clocksources() buffer overflow problem
From: Miao Xie <miaox@xxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxx>
Cc: WANG Cong <xiyou.wangcong@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: john stultz <johnstul@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/time/clocksource.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)
diff -puN kernel/time/clocksource.c~time-fix-sysfs_show_availablecurrent_clocksources-buffer-overflow-problem kernel/time/clocksource.c
--- a/kernel/time/clocksource.c~time-fix-sysfs_show_availablecurrent_clocksources-buffer-overflow-problem
+++ a/kernel/time/clocksource.c
@@ -342,15 +342,13 @@ void clocksource_change_rating(struct cl
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;
}
/*
_
Patches currently in -mm which might be from miaox@xxxxxxxxxxxxxx are
sysfs-fix-off-by-one-error-in-fill_read_buffer.patch
time-fix-sysfs_show_availablecurrent_clocksources-buffer-overflow-problem.patch
-
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