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[2003:cb:c742:c800:d74f:aec6:f8ac:558]) by smtp.gmail.com with ESMTPSA id f18-20020adfdb52000000b00307d20546e6sm7090571wrj.27.2023.05.22.02.01.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 22 May 2023 02:01:11 -0700 (PDT) Message-ID: <7883b08b-6bdc-a214-96a3-3f5bc1d36da4@redhat.com> Date: Mon, 22 May 2023 11:01:10 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH v2 4/5] mm: Add a NO_INHERIT flag to the PR_SET_MDWE prctl Content-Language: en-US To: Florent Revest , linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: akpm@linux-foundation.org, catalin.marinas@arm.com, anshuman.khandual@arm.com, joey.gouly@arm.com, mhocko@suse.com, keescook@chromium.org, peterx@redhat.com, izbyshev@ispras.ru, broonie@kernel.org, szabolcs.nagy@arm.com, kpsingh@kernel.org, gthelen@google.com, toiwoton@gmail.com References: <20230517150321.2890206-1-revest@chromium.org> <20230517150321.2890206-5-revest@chromium.org> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230517150321.2890206-5-revest@chromium.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 17.05.23 17:03, Florent Revest wrote: > This extends the current PR_SET_MDWE prctl arg with a bit to indicate > that the process doesn't want MDWE protection to propagate to children. > > To implement this no-inherit mode, the tag in current->mm->flags must be > absent from MMF_INIT_MASK. This means that the encoding for "MDWE but > without inherit" is different in the prctl than in the mm flags. This > leads to a bit of bit-mangling in the prctl implementation. > > Signed-off-by: Florent Revest > --- > include/linux/sched/coredump.h | 10 ++++++++++ > include/uapi/linux/prctl.h | 1 + > kernel/fork.c | 2 +- > kernel/sys.c | 24 +++++++++++++++++++++--- > tools/include/uapi/linux/prctl.h | 1 + > 5 files changed, 34 insertions(+), 4 deletions(-) > > diff --git a/include/linux/sched/coredump.h b/include/linux/sched/coredump.h > index 0ee96ea7a0e9..11f5e3dacb4e 100644 > --- a/include/linux/sched/coredump.h > +++ b/include/linux/sched/coredump.h > @@ -91,4 +91,14 @@ static inline int get_dumpable(struct mm_struct *mm) > MMF_DISABLE_THP_MASK | MMF_HAS_MDWE_MASK) > > #define MMF_VM_MERGE_ANY 29 > +#define MMF_HAS_MDWE_NO_INHERIT 30 > + > +#define MMF_INIT_FLAGS(flags) ({ \ > + unsigned long new_flags = flags; \ > + if (new_flags & (1UL << MMF_HAS_MDWE_NO_INHERIT)) \ > + new_flags &= ~((1UL << MMF_HAS_MDWE) | \ > + (1UL << MMF_HAS_MDWE_NO_INHERIT)); \ > + new_flags & MMF_INIT_MASK; \ > +}) Why the desire for macros here? :) We have a single user of MMF_INIT_FLAGS, why not inline or use a proper inline function? -- Thanks, David / dhildenb