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Mon, 23 Oct 2023 10:44:28 -0700 (PDT) MIME-Version: 1.0 References: <20231016143828.647848-1-jeffxu@chromium.org> In-Reply-To: From: Jeff Xu Date: Mon, 23 Oct 2023 10:44:16 -0700 Message-ID: Subject: Re: [RFC PATCH v1 0/8] Introduce mseal() syscall To: Linus Torvalds Cc: Pedro Falcato , Jeff Xu , Matthew Wilcox , akpm@linux-foundation.org, keescook@chromium.org, sroettger@google.com, jorgelo@chromium.org, groeck@chromium.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, jannh@google.com, surenb@google.com, alex.sierra@amd.com, apopple@nvidia.com, aneesh.kumar@linux.ibm.com, axelrasmussen@google.com, ben@decadent.org.uk, catalin.marinas@arm.com, david@redhat.com, dwmw@amazon.co.uk, ying.huang@intel.com, hughd@google.com, joey.gouly@arm.com, corbet@lwn.net, wangkefeng.wang@huawei.com, Liam.Howlett@oracle.com, lstoakes@gmail.com, mawupeng1@huawei.com, linmiaohe@huawei.com, namit@vmware.com, peterx@redhat.com, peterz@infradead.org, ryan.roberts@arm.com, shr@devkernel.io, vbabka@suse.cz, xiujianfeng@huawei.com, yu.ma@intel.com, zhangpeng362@huawei.com, dave.hansen@intel.com, luto@kernel.org, linux-hardening@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 247A6C0007 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: bkuuyk6b7hs7nx6ywbimg19iypdswkj7 X-HE-Tag: 1698083068-456930 X-HE-Meta: U2FsdGVkX1/BLrfXKdwYhSKDiLMXMT0spOIMfPPWqvALsLoMO8YIgiCiOZ0bryE8dg/qk4CDK7pasOxC169/c0k+ex30uG2Vdzyppnck8Gs6Ls2umz1AajBAs214AWdc94zwKMddE0BSPkCULRFGOdD91oSl9GTWVssqXFPS7czXbGLD4MzTqS+BpEp7b4Jd+mmGuE82fh1f37XH/cbw/AlBZQAtp3hnH/gI17fPxOIM0Em5vyFmjeeRiCGR00tc4/8hPWQL2e23OipPtWfcksucEABnJFy7IlCnnq2aJalJbd34Ut4QzDxfZ64H3BTWIQkxXbv+RU6ottgTPZ3Mh0s3hGA17D9Yswkgrwz0o2cL7+2/nzredvkTfiyhlvBjsUUjtOOJa0R/RHKMbWtpYTontJ1FDSO8h+KG6t4VouvKYDlF5areRaraW1csx2i6J6HfH9bki8cMmcx5u16MwzjNmkGuXuO1HRmA5uD12JNMGrMfJZm6i1AgUJEMG4Wtk3r+oOKYtV+KFOIJ5goPXpoBk0RLKfCiDxolJ8PkG+ZeQNdIPLLx0F9MU916pVDfSDZzbUWXBIgAjfFU4YU5W+arwIAxhayK1WAmZkRbqurVLXnqv8MIENJm0ZcGn+73S2pn9G7zyIiYsVZAYZjOw1dWbaB0Sn47ZWxl9zDD6/0+TxDX3HuhUqKbugB72h+QCC3m8kwHZVDpmsLguUuwJsexCbdKdQmD9esQ6GEUgoerjtofbivDX0gCYch3o7mvTd+johFg/iNKIPd5yWVFiZEMeUIHVkt/sMo1kdAJf2xH6JjA8rt1SbYs8fivqmVtYLhMHuPqX2qy7REQ0MnxnV1pKIuG6r8IrcnSO4VFAUsmLi9E/ohaRrUeeskWdSawdvAUVswOI0gGd1XcaBqZLNDErsxTM/WTh0JMkpaXRkmfSWtu9xYB7JDBla3Q6xJoXHFUJMHfQo6p+k8BZk/ DQvjpUHe iyZga7j888kpBrowjNHR+zIWRhrCeHiXeiwwcbCli0xwEihunQ9mpSSiBjTy4bbxWg1iWzCEI2/6PWNF/XMM1F8l+9scqKEbePNpDyHAry9AgxaMT0UEwaE2JmxbTK5EmThF9UKicIak00oMnWSE399ypRUumjDHHLHF3s1bf4wrIV4CZ+2Iu3Y8WnkAZjozMuJOm1UKRcRU1+EVOaodsnXhJDz4fN0XUVPfTff6h4meYdcEsiTvMF4wDyZoY/2DW8c/TIjCMuq31ZrhbHBbvO8kjaQ6hmTFpA70onP0owTbo7c3YeWmohMw/gEmW3ZIlA4PE9iV0mBSpjfz9e3MNGP0b2A== 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: List-Subscribe: List-Unsubscribe: On Thu, Oct 19, 2023 at 4:06=E2=80=AFPM Linus Torvalds wrote: > > On Thu, 19 Oct 2023 at 15:47, Pedro Falcato wro= te: > > > > > > For mprotect()/mmap(), is Linux implementation limited by POSIX ? > > > > No. POSIX works merely as a baseline that UNIX systems aim towards. > > You can (and very frequently do) extend POSIX interfaces (in fact, > > it's how most of POSIX was written, through sheer > > "design-by-committee" on a bunch of UNIX systems' extensions). > > We can in extreme circumstances actually go further than that, and not > only extend on POSIX requirements, but actively even violate them. > > It does need a very good reason, though, but it has happened when > POSIX requirements were simply actively wrong. > > For example, at one point POSIX required > > int accept(int s, struct sockaddr *addr, size_t *addrlen); > > which was simply completely wrong. It's utter shite, and didn't > actually match any reality. > > The 'addrlen' parameter is 'int *', and POSIX suddenly trying to make > it "size_t" was completely unacceptable. > > So we ignored it, told POSIX people that they were full of sh*t, and > they eventually fixed it in the next version (by introducing a > "socklen_t" that had better be the same as "int"). > > So POSIX can simply be wrong. > > Also, if it turns out that we had some ABI that wasn't > POSIX-compatible, the whole "don't break user space" will take > precedence over any POSIX concerns, and we will not "fix" our system > call if people already use our old semantics. > > So in that case, we generally end up with a new system call (or new > flags) instead. > > Or sometimes it just is such a small detail that nobody cares - POSIX > also has a notion of documenting areas of non-conformance, and people > who really care end up having notions like "conformance vs _strict_ > conformance". > > Linus > Thanks Linus for clarifying the guidelines on POSIX in Linux. -Jeff