Messages in this thread | | | Date | Mon, 8 Jun 2020 09:49:13 -0700 | 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) | From | sdf@google ... |
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On 06/08, Alexei Starovoitov wrote: > On Mon, Jun 8, 2020 at 6:05 AM Christoph Hellwig <hch@lst.de> wrote: > > > > 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.
> adding Stanislav. I think he's looking into this already. Yeah, I'm looking at it from the get/setsockopt point of view. I'm currently trying to bypass allocating a buffer if it's greater than PAGE_SIZE. I suppose for sysctls we should try to do something similar?
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