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

Alok Kataria
2009-02-11T22:54:16Z

Hi Tetsuo,

Thanks for reporting this. Yes i tried it here with a slightly
different .config and i did see the problem. I will try to figure out
what is happening over here, but before doing that let me ask if this
bug is only in the stable series ?
Do we know for which kernel does the "nolapic" option doesn't hit this
bug ?

Also, I assume its not present in 2.6.29-rc ?

Thanks,
Alok

On Mon, 2009-02-09 at 03:19 -0800, Tetsuo Handa wrote:
> 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;
> }