On Tue, Mar 16, 2021 at 10:01:46AM +0200, Topi Miettinen wrote: > On 15.3.2021 19.47, Uladzislau Rezki wrote: > > On Mon, Mar 15, 2021 at 09:16:26AM -0700, Kees Cook wrote: > > > On Mon, Mar 15, 2021 at 01:24:10PM +0100, Uladzislau Rezki wrote: > > > > On Mon, Mar 15, 2021 at 11:04:42AM +0200, Topi Miettinen wrote: > > > > > What's the problem with that? It seems to me that nothing relies on specific > > > > > addresses of the chunks, so it should be possible to randomize these too. > > > > > Also the alignment is honored. > > > > > > > > > My concern are: > > > > > > > > - it is not a vmalloc allocator; > > > > - per-cpu allocator allocates chunks, thus it might be it happens only once. It does not allocate it often; > > > > > > That's actually the reason to randomize it: if it always ends up in the > > > same place at every boot, it becomes a stable target for attackers. > > > > > Probably we can randomize a base address only once when pcpu-allocator > > allocates a fist chunk during the boot. > > > > > > - changing it will likely introduce issues you are not aware of; > > > > - it is not supposed to be interacting with vmalloc allocator. Read the > > > > comment under pcpu_get_vm_areas(); > > > > > > > > Therefore i propose just not touch it. > > > > > > How about splitting it from this patch instead? Then it can get separate > > > testing, etc. > > > > > It should be split as well as tested. > > Would you prefer another kernel option `randomize_percpu_allocator=1`, or > would it be OK to make it a flag in `randomize_vmalloc`, like > `randomize_vmalloc=3`? Maybe the latter would not be compatible with static > branches. > I think it is better to have a separate option, because there are two different allocators. -- Vlad Rezki
