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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue, 12 Dec 2023 16:39:31 -0800
Message-ID: <CAHk-=wgn02cpoFEDQGgS+5BUqA2z-=Ks9+PNd-pEJy8h+NOs5g@mail.gmail.com>
Subject: Re: [RFC PATCH v3 11/11] mseal:add documentation
To:     jeffxu@chromium.org
Cc:     akpm@linux-foundation.org, keescook@chromium.org, jannh@google.com,
        sroettger@google.com, willy@infradead.org,
        gregkh@linuxfoundation.org, jeffxu@google.com,
        jorgelo@chromium.org, groeck@chromium.org,
        linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
        linux-mm@kvack.org, pedro.falcato@gmail.com, dave.hansen@intel.com,
        linux-hardening@vger.kernel.org, deraadt@openbsd.org
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On Tue, 12 Dec 2023 at 15:17, <jeffxu@chromium.org> wrote:
> +
> +**types**: bit mask to specify the sealing types, they are:

I really want a real-life use-case for more than one bit of "don't modify".

IOW, when would you *ever* say "seal this area, but MADV_DONTNEED is ok"?

Or when would you *ever* say "seal this area, but mprotect()" is ok.

IOW, I want to know why we don't just do the BSD immutable thing, and
why we need this multi-level sealing thing.

               Linus