On Thu, Jun 09, 2022 at 11:11:54AM +0100, Will Deacon wrote: > On Thu, Jun 09, 2022 at 11:44:09AM +0800, Kefeng Wang wrote: > > On 2022/6/9 10:49, Vasily Averin wrote: > > > mem_cgroup_from_obj(): > > > ffff80000836cf40: d503245f bti c > > > ffff80000836cf44: d503201f nop > > > ffff80000836cf48: d503201f nop > > > ffff80000836cf4c: d503233f paciasp > > > ffff80000836cf50: d503201f nop > > > ffff80000836cf54: d2e00021 mov x1, #0x1000000000000 // #281474976710656 > > > ffff80000836cf58: 8b010001 add x1, x0, x1 > > > ffff80000836cf5c: b25657e4 mov x4, #0xfffffc0000000000 // #-4398046511104 > > > ffff80000836cf60: d34cfc21 lsr x1, x1, #12 > > > ffff80000836cf64: d37ae421 lsl x1, x1, #6 > > > ffff80000836cf68: 8b040022 add x2, x1, x4 > > > ffff80000836cf6c: f9400443 ldr x3, [x2, #8] > > > > > > x5 : ffff80000a96f000 x4 : fffffc0000000000 x3 : ffff80000ad5e680 > > > x2 : fffffe00002bc240 x1 : 00000200002bc240 x0 : ffff80000af09740 > > > > > > x0 = 0xffff80000af09740 is an argument of mem_cgroup_from_obj() > > > according to System.map it is init_net > > > > > > This issue is caused by calling virt_to_page() on address of static variable init_net. > > > Arm64 consider that addresses of static variables are not valid virtual addresses. > > > On x86_64 the same API works without any problem. > > This just depends on whether or not the kernel is running out of the linear > mapping or not. On arm64, we use the vmalloc area for the kernel image and > so virt_to_page() won't work, just like it won't work for modules on other > architectures. > > How are module addresses handled by mem_cgroup_from_obj()? It doesn't look like they are handled in any way. It just expects the pointer to be a linear map one. Something like below: diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 27cebaa53472..795bf3673fa7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2860,6 +2860,11 @@ struct mem_cgroup *mem_cgroup_from_obj(void *p) if (mem_cgroup_disabled()) return NULL; + if (is_module_address((unsigned long)p)) + return NULL; + else if (is_kernel((unsigned long)p)) + return NULL; + folio = virt_to_folio(p); /* -- Catalin
