Re: [Bug #12409] NULL pointer dereference at get_stats()

Tetsuo Handa
2009-02-09T11:19:16Z

Hello.

> Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=12409
> Subject : NULL pointer dereference at get_stats()
> Submitter : Tetsuo Handa <penguin-kernel-1yMVhJb1mP/7nzcFbJAaVXf5DAMn2ifp@public.gmane.org>
> Date : 2008-12-30 12:53 (21 days old)
> References : http://marc.info/?l=linux-kernel&m=123064167008695&w=4
> Handled-By : Frederik Deweerdt <frederik.deweerdt-kjvbsxwSFqI@public.gmane.org>

I made custom initramfs and tested on native environment and KVM and VMware.
This problem happened only in VMware.

Alok and Daniel (cc: added), can you reproduce this problem?

Problem description:

Compiling 2.6.28.4 using config at http://I-love.SAKURA.ne.jp/tmp/config-2.6.28-bug
and booting with "nolapic" option on x86 machine with 2 CPUs, NULL pointer
dereference happens at get_stats() because for_each_possible_cpu() reaches
CPU 1 while "nolapic" option should prevent for_each_possible_cpu() from
reaching CPU 1.

Compiling 2.6.28.4 using config at http://I-love.SAKURA.ne.jp/tmp/config-2.6.28-nobug
(all options in "Power management and ACPI options" section disabled)
solves this problem.

Also, this problem seems to be VMware specific.
I couldn't reproduce this problem on native environment and KVM.

Native environment (no problem):

CentOS 5.2 (x86_64) and Ubuntu 8.04 (i386) on ThinkPad X60

KVM environment (no problem):

kvm -kernel /boot/vmlinuz-2.6.28.4 -initrd /boot/init -net none -hda /var/tmp/image.img -vnc xx.xx.xx.xx:0 --append "ro nolapic" -smp 2
on Ubuntu 8.04 (i386) on ThinkPad X60

VMware environment (problematic):

Debian Sarge (i386) / CentOS 5.2 (i386) on VMware workstation 6.5.1 (x86_64)
on CentOS 5.2 (x86_64) on ThinkPad X60

Problematic kernel versions:

2.6.27.x and 2.6.28.x .

Regards.

----- Custom initramfs -----
/*
gcc -Wall -O3 -static -o init init.c
echo init | cpio -o -H newc | gzip -9 > /boot/init
*/
#include <sys/mount.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>

int main(int argc, char *argv[]) {
FILE *fp;
char buffer[1024];
memset(buffer, 0, sizeof(buffer));
mkdir("/proc", 0755);
mount("none", "/proc", "proc", 0, NULL);
fp = fopen("/proc/cpuinfo", "r");
while (fgets(buffer, sizeof(buffer) - 1, fp))
if (strstr(buffer, "processor"))
printf("%s", buffer);
fclose(fp);
fp = fopen("/proc/cmdline", "r");
fgets(buffer, sizeof(buffer) - 1, fp);
fclose(fp);
printf("%s", buffer);
fflush(stdout);
if (mkdir("/sys", 0755) || mount("/sys/", "/sys/", "sysfs", 0, NULL)) {
printf("mount failed\n");
while (1)
sleep(1);
}
fp = fopen("/sys/class/net/lo/statistics/rx_packets", "r");
if (!fp) {
printf("open failed\n");
while (1)
sleep(1);
}
while (fgets(buffer, sizeof(buffer) - 1, fp))
;
fclose(fp);
printf("done\n");
while (1)
sleep(1);
return 0;
}