Re: namespaces?: bug at mm/slub.c:2750

Vegard Nossum
2009-02-11T10:48:54Z

On Wed, Feb 11, 2009 at 9:07 AM, Andrew Morton
<akpm@linux-foundation.org> wrote:
>> In case you missed it, KOSAKI Motohiro posted a similar stack-trace
>> (but not the same BUG) in this thread:
>> http://lkml.org/lkml/2009/2/10/7
>>
>
> Both traces include the newly-added put_cred_rcu(). Suspicious.
>

I have this test case which triggers it regularly after some minutes:

#include <sys/wait.h>
#include <sys/types.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

int main(int argc, char* argv[])
{
unsigned int i;

if (fork() == 0) {
while (1)
system("echo -n .");
}

for (i = 0; i < 2; ++i) {
if (fork() == 0) {
while (1) {
setreuid(0, 0xcafeba);
setreuid(0xcafeba, 0);

setreuid(0, 0xcafebb);
setreuid(0xcafebb, 0);
}

exit(EXIT_SUCCESS);
}
}

while (!(wait(NULL) == -1 && errno == ECHILD))
;

return 0;
}

It seems to be the combination of exec() and setreuid(), but I
couldn't get it to work with just exec() instead of system(). It is
possible that CONFIG_USER_SCHED must be =y for this to work. It can
probably be simplified too...

Vegard

--
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
-- E. W. Dijkstra, EWD1036