Messages in this thread | | | Date | Mon, 8 Jun 2020 15:05:03 +0200 | From | Christoph Hellwig <> | Subject | Re: WARNING: CPU: 1 PID: 52 at mm/page_alloc.c:4826 __alloc_pages_nodemask (Re: [PATCH 5/5] sysctl: pass kernel pointers to ->proc_handler) |
| |
On Mon, Jun 08, 2020 at 09:45:49AM +0200, Vegard Nossum wrote: > 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;
Doesn't help if we don't know the exact limit yet. But we can put some arbitrary but reasonable limit like KMALLOC_MAX_SIZE on the sysctls and see if this sticks.
| |