On 2020-06-08 08:51, Christoph Hellwig wrote:
On Thu, Jun 04, 2020 at 10:22:21PM +0200, Vegard Nossum wrote:
It's easy to reproduce by just doing
read(open("/proc/sys/vm/swappiness", O_RDONLY), 0, 512UL * 1024 * 1024
* 1024);
or so. Reverting the commit fixes the issue for me.
Yes, doing giant allocations will fail and trace. We have to options
here that both seems sensible:
- trunate sysctrl calls to some sensible length
- (optionally) use vmalloc
Is this a real application or just a test case trying to do the
stupidmost possible thing?
Just a test case.
Allowing the kernel to allocate an unbounded amount of memory on behalf
of userspace is an easy DOS.
All the length checks were already in there, e.g.
static int cmm_timeout_handler(struct ctl_table *ctl, int write,
void __user *buffer, size_t *lenp, loff_t
*ppos)
{
char buf[64], *p;
[...]
len = min(*lenp, sizeof(buf));
if (copy_from_user(buf, buffer, len))
return -EFAULT;
Vegard
