Oleg Nesterov <o...@redhat.com> writes:
> On 05/04, Eric W. Biederman wrote:
>>
>> Oleg Nesterov <o...@redhat.com> writes:
>>
>> > OK, what about exec() ? mm_init_memcg() initializes bprm->mm->memcg early
>> > in
>> > bprm_mm_init(). What if the execing task migrates before exec_mmap() ?
>>
>> We need the the cgroup when the mm is initialized. That way we have the
>> cgroup information when initializing the mm.
>
> Yes, we need to initialize new_mm->memcg but iiuc mostly for the error path,
>
>> I don't know if a lock preventing changing the cgroup in exec or just
>> a little bit of code in exec_mmap to ensure mm->memcg is properly set
>> is the better approach.
>
> I'd vote for the change in exec_mmap(). This way mm_init_memcg() can just
> nullify mm->memcg.
There is at least one common path where we need the memory control group
properly initialized so memory allocations don't escape the memory
control group.
do_execveat_common
copy_strings
get_arg_page
get_user_pages_remote
__get_user_pages_locked
__get_user_pages
faultin_page
handle_mm_fault
count_memcg_event_mm
__handle_mm_fault
handle_pte_fault
do_anonymous_page
mem_cgroup_try_charge
I am surprised I can't easily find more. Apparently in load_elf_binary
we call elf_mmap after set_new_exec and install_exec_creds, making
a gracefull recovery from elf_mmap failures impossible.
In any case we most definitely need the memory control group properly
setup before exec_mmap.
Eric
