Re: [PATCHv4 3/8] mm: Pass down mm_struct to untagged_addr()

[Alexander Potapenko]

Kirill,


> diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c
> index feeb935a2299..abc096a68f05 100644
> --- a/lib/strnlen_user.c
> +++ b/lib/strnlen_user.c
> @@ -97,7 +97,7 @@ long strnlen_user(const char __user *str, long count)
>                 return 0;
>
>         max_addr = TASK_SIZE_MAX;
> -       src_addr = (unsigned long)untagged_addr(str);
> +       src_addr = (unsigned long)untagged_addr(current->mm, str);

In a downstream kernel with LAM disabled I'm seeing current->mm being
NULL at this point, because strnlen_user() is being called by
kdevtmpfs.
IIUC current->mm is only guaranteed to be non-NULL in the userspace
process context, whereas untagged_addr() may get called in random
places.

Am I missing something?



-- 
Alexander Potapenko
Software Engineer

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