Re: [PATCH v19 04/15] mm: untag user pointers passed to memory syscalls

[Catalin Marinas]

On Tue, Jul 23, 2019 at 07:58:41PM +0200, Andrey Konovalov wrote:
> This patch is a part of a series that extends kernel ABI to allow to pass
> tagged user pointers (with the top byte set to something else other than
> 0x00) as syscall arguments.
> 
> This patch allows tagged pointers to be passed to the following memory
> syscalls: get_mempolicy, madvise, mbind, mincore, mlock, mlock2, mprotect,
> mremap, msync, munlock, move_pages.
> 
> The mmap and mremap syscalls do not currently accept tagged addresses.
> Architectures may interpret the tag as a background colour for the
> corresponding vma.
> 
> Reviewed-by: Khalid Aziz <khalid.aziz@xxxxxxxxxx>
> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> ---
>  mm/madvise.c   | 2 ++
>  mm/mempolicy.c | 3 +++
>  mm/migrate.c   | 2 +-
>  mm/mincore.c   | 2 ++
>  mm/mlock.c     | 4 ++++
>  mm/mprotect.c  | 2 ++
>  mm/mremap.c    | 7 +++++++
>  mm/msync.c     | 2 ++
>  8 files changed, 23 insertions(+), 1 deletion(-)

More back and forth discussions on how to specify the exceptions here.
I'm proposing just dropping the exceptions and folding in the diff
below.

Andrew, if you prefer a standalone patch instead, please let me know:

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