|
| From: | Paolo Bonzini |
| Subject: | [Qemu-devel] Re: [PATCH] fix qruncom compilation problems |
| Date: | Fri, 10 Dec 2010 09:53:04 +0100 |
| User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.12) Gecko/20101103 Fedora/1.0-0.33.b2pre.fc14 Lightning/1.0b3pre Mnenhy/0.8.3 Thunderbird/3.1.6 |
On 12/09/2010 06:29 PM, Stefano Bonifazi wrote:
how can one think that addresses around zero are free for a mapping??
Addresses around zero are always free, because if they weren't you couldn't detect NULL pointer dereferences reliably.
mmap-ing at zero thus is a tricky operation, because it removes the possibility to detect NULL pointer dereferences. What's worse, such ability would be lost even for _kernel_ dereferences of NULL, thus opening a large security hole for privilege-escalation or kernel exploits. So, mmap-ing addresses close to zero is restricted to root.
Paolo
| [Prev in Thread] | Current Thread | [Next in Thread] |