Re: [RFC PATCH 09/10] uaccess: Refuse and warn on more user accesses without an mm

[sashiko-bot@kernel.org]

> Several generic user access paths don't go through the copy helpers
> that check for a NULL current->mm. Add the uaccess_without_mm() check to
> them as well, so that they warn and fail without attempting the access:
> 
>  - __scoped_user_access_begin(), covering scoped_user_*_access() and
>    get_user_inline()/put_user_inline() on all architectures, including
>    when masked user access is used.
>  - strnlen_user().
>  - check_zeroed_user().
>  - The iov_iter user copy routines that call into architecture-specific
>    helpers: copy_to_user_iter_mc() (copy_mc_to_user()),
>    copy_from_user_iter_nocache() (copy_from_user_inatomic_nontemporal()),
>    copy_from_user_iter_flushcache() (copy_from_user_flushcache()) and
>    zero_to_user_iter() (clear_user()).
> 
> Only check for a NULL mm here rather than using uaccess_should_fail(),
> so as not to start injecting failures in these paths.
> 
> Paths implemented entirely by architectures, e.g. get_user(),
> put_user(), clear_user(), and direct users of user_access_begin() or
> masked_user_access_begin(), are still not covered.
> 
> Signed-off-by: James Houghton <jthoughton@google.com>

Sashiko has reviewed this patch and found no issues.

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