Messages in this thread | | | From | Alexander Potapenko <> | Date | Tue, 5 Jul 2022 17:42:21 +0200 | Subject | Re: [PATCHv4 3/8] mm: Pass down mm_struct to untagged_addr() |
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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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