Re: 3.4-rc7: BUG: Bad rss-counter state mm:ffff88040b56f800 idx:1val:-59

[Konstantin Khlebnikov]

Martin Mokrejs wrote:
> Konstantin Khlebnikov wrote:
> > Martin Mokrejs wrote:
> > > Andrew Morton wrote:
> > > > On Wed, 30 May 2012 00:18:31 +0400
> > > > Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>   wrote:
> > > >
> > > > > Oleg Nesterov wrote:
> > > > > > On 05/22, Andrew Morton wrote:
> > > > > > > Also, I have a note here that Oleg was unhappy with the patch.  Oleg
> > > > > > > happiness is important.  Has he cheered up yet?
> > > > > >
> > > > > > Well, yes, I do not really like this patch ;) Because I think there is
> > > > > > a more simple/straightforward fix, see below. In my opinion it also
> > > > > > makes the original code simpler.
> > > > > >
> > > > > > But. Obviously this is subjective, I can't prove my patch is "better",
> > > > > > and I didn't try to test it.
> > > > > >
> > > > > > So I won't argue with Konstantin who dislikes my patch, although I
> > > > > > would like to know the reason.
> > > > >
> > > > > I don't remember why I dislike your patch.
> > > > > For now I can only say ACK )
> > > >
> > > > We'll need a changelogged signed-off patch, please Oleg.  And some evidence
> > > > that it was tested would be nice ;)
> > >
> > > I will reboot in few hours, finally after few days ... I am running this first
> > > patch. I will try to test the second/alternative patch more quickly. Sorry for
> > > the delay.
> >
> > easiest way trigger this bug:
> >
> > #define _GNU_SOURCE
> > #include<unistd.h>
> > #include<sched.h>
> > #include<sys/syscall.h>
> > #include<sys/mman.h>
> >
> > static inline int sys_clone(unsigned long flags, void *stack, int *ptid, int *ctid)
> > {
> >      return syscall(SYS_clone, flags, stack, ptid, ctid);
> > }
> >
> > int main(int argc, char **argv)
> > {
> >      void *page;
> >
> >      page = mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
> >      sys_clone(CLONE_VFORK | CLONE_VM | CLONE_CHILD_CLEARTID, NULL, NULL, page);
> > }
>
> I am getting segfaults with this.
>
> (gdb) where
> #0  0x0000000000000000 in ?? ()
> #1  0x00007f430f70a7e0 in __elf_set___libc_subfreeres_element_free_mem__ () from /lib64/libc.so.6
> #2  0x00007f430f70a7e8 in __elf_set___libc_atexit_element__IO_cleanup__ () from /lib64/libc.so.6
> #3  0x0000000000000001 in ?? ()
> #4  0x0000000000000000 in ?? ()
> (gdb)
>
> What number should I give it as an argument? ;-)

there is no arguments.

yeah it corrupts stack. I'm too lazy to write it properly =)
but on non-patched kernel it also triggers this bug:
[206732.025131] BUG: Bad rss-counter state mm:ffff88000d8a6c80 idx:1 val:-1

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