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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 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> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 0F127180016 X-Stat-Signature: 71xgcmje4iar6xdrbc3mpx9zkrdfayoq X-Rspam-User: X-HE-Tag: 1684746078-578760 X-HE-Meta: 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 QuP2QYwW pEUvg65kwKE9WAjatVwGilXpg01to+HgBFZEXSFARr/OgsfXtW0UPiI2/e13QgkhxGvYnIrINlZL2ADAfOttKIPnfrJR/KzCUX/tuhIKVHFw/BUSoe00/M3g7dCBJn96oMDzTddVxHTqyngkhxKNj8QHkpXOyeVi6gsp3g7cLgN/2CXuFTsZOjMA8NSatXAkSe4g7OL0DilTVR89jt7HPQdoWWzR6xL3DvhIj4K4xaeawLnY0k0rGlRbj0+vg6Bss/KpH+BtkvIXs8jSFoOwacG4EFdpM1hAuEKPR45vxu5N0Da6F28IqF9D0V7l8mBKQxGrGNxoK99vSjfipcrPvI6CeNZLMV7cWi3p0yTqzhTmSPmmyx8HaPKz1wY6ahYddqMsTv5W+FYhppFiG7O9snMMSZxEZ68uCEuOlLbIeS31y5TmGNPs/vYsQrDhBkS1ilwhGd363b3wPkqPadPfHopMP7DMYwpSpq/jWotvB584aCnM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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