Messages in this thread | | | Subject | Re: [PATCH] mm/vmalloc: randomize vmalloc() allocations | From | Topi Miettinen <> | Date | Wed, 9 Dec 2020 21:08:23 +0200 |
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On 3.12.2020 8.58, Mike Rapoport wrote: > On Wed, Dec 02, 2020 at 08:49:06PM +0200, Topi Miettinen wrote: >> On 1.12.2020 23.45, Topi Miettinen wrote: >>> Memory mappings inside kernel allocated with vmalloc() are in >>> predictable order and packed tightly toward the low addresses. With >>> new kernel boot parameter 'randomize_vmalloc=1', the entire area is >>> used randomly to make the allocations less predictable and harder to >>> guess for attackers. >>> >> >> This also seems to randomize module addresses. I was going to check that >> next, so nice surprise! > > Heh, that's because module_alloc() uses vmalloc() in that way or another :)
The modules are still allocated from their small (1.5GB) separate area instead of the much larger (32TB/12.5PB) vmalloc area, which would greatly improve ASLR for the modules. To fix that, I tried to to #define MODULES_VADDR to VMALLOC_START etc. like x86_32 does, but then kernel dies very early without even any output.
-Topi
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