[RFC PATCH v2 0/2] Randomization of address chosen by mmap.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



> On 23 Mar 2018, at 15:48, Matthew Wilcox <willy at infradead.org> wrote:
> 
> On Thu, Mar 22, 2018 at 07:36:36PM +0300, Ilya Smith wrote:
>> Current implementation doesn't randomize address returned by mmap.
>> All the entropy ends with choosing mmap_base_addr at the process
>> creation. After that mmap build very predictable layout of address
>> space. It allows to bypass ASLR in many cases. This patch make
>> randomization of address on any mmap call.
> 
> Why should this be done in the kernel rather than libc?  libc is perfectly
> capable of specifying random numbers in the first argument of mmap.
Well, there is following reasons:
1. It should be done in any libc implementation, what is not possible IMO;
2. User mode is not that layer which should be responsible for choosing
random address or handling entropy;
3. Memory fragmentation is unpredictable in this case

Off course user mode could use random ?hint? address, but kernel may
discard this address if it is occupied for example and allocate just before
closest vma. So this solution doesn?t give that much security like 
randomization address inside kernel.


[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]

  Powered by Linux