Questions tagged [kernel]

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24
votes
1answer
4k views

DMA attacks despite IOMMU isolation

If you're already familiar with PCI behavior and Linux's handling of DMA buffers, skip to the third section for my actual question. Otherwise read on for a small summary of how PCI devices perform ...
39
votes
2answers
14k views

What is protection ring -1?

Due to the Lenovo firmware ThinkPwn bug I'm trying to understand privileges and rings. If the kernel is Ring 0 and SMM (System Management Mode) is Ring -2, what could be in between that is Ring -1?
69
votes
7answers
23k views

What is the possible impact of dirtyc0w a.k.a. “Dirty COW” bug?

I heard about Dirty COW but couldn't find any decent writeup on the scope of the bug. It looks like the exploit can overwrite any non-writable file, which makes me guess that local root is possible ...
27
votes
2answers
2k views

Methods root can use to elevate itself to kernel mode

When most Linux users hear "root", they think of the maximum possible privilege on a computer. Some even think that root runs in ring 0. But in reality, root is just a regular user running in ring 3, ...
26
votes
4answers
3k views

How Do Rootkits & Other Low-Level Malware Still Manage to Load on Systems Protected by Secure Boot (and TB/MB)?

Let me try asking my question this way... Let's say that I'm a offensive cyber Bad Guy working for a foreign state-sponsored Advanced Persistent Threat unit. My unit is charged with, say, stealing ...
4
votes
1answer
265 views

Does printk() cause any security issues?

I'm asking myself if the function printk() causes security issues on Linux. When an attacker has user level access to the system, does it make his life easier if he has access to kernel pointers? Does ...
15
votes
3answers
21k views

Pros and cons of disabling TCP timestamps

So, lynis informs me that I should unset net.ipv4.tcp_timestamps. I know that's a bad thing because an attacker could figure out which updates that require restarting the machine I haven't applied, or ...
24
votes
1answer
2k views

Which attacks are known that exploit the vulnerability known as Spectre?

As reported yesterday the Linux and Windows kernels will receive a security update pretty soon to close vulnerabilities that concern 'kernel memory leaking'. What exactly the design flaw is, that was ...
7
votes
1answer
1k views

Security essentials for a embedded Linux device

We are prototyping a security camera product using Raspberry Pi 3 as the hardware platform. The camera has capability to connect to the cloud over internet as well as offline processing when the ...
1
vote
2answers
186 views

Can a running kernel be protected by underlying rings, BIOS etc?

I mostly found examples the other way around: compromising the OS e.g. through a compromised BIOS or Intel ME. But are there known examples where stuff runs underneath the kernel and can be used to ...
15
votes
2answers
3k views

Does a compromised kernel give complete control over a device?

It seems that a recent vulnerability in WiFi firmware allows an attacker to run code in kernel space, e.g. replace a kernel function with malicious code. In Android/Linux: Would that give an ...
6
votes
1answer
3k views

Can a kernel exploit compromise an OpenVZ host?

As OpenVZ runs on a lot of virtual servers, I would like to know how kernel exploits would affect the whole system. Would it be possible to break out of an OpenVZ container (virtuozzo, etc) with a ...