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Wed, 23 Oct 2024 09:06:32 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id m0t+IJi8GGcIJQAAD6G6ig (envelope-from ); Wed, 23 Oct 2024 09:06:32 +0000 Message-ID: Date: Wed, 23 Oct 2024 11:06:32 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 0/5] implement lightweight guard pages Content-Language: en-US To: Dmitry Vyukov , Lorenzo Stoakes Cc: David Hildenbrand , fw@deneb.enyo.de, James.Bottomley@hansenpartnership.com, Liam.Howlett@oracle.com, akpm@linux-foundation.org, arnd@arndb.de, brauner@kernel.org, chris@zankel.net, deller@gmx.de, hch@infradead.org, ink@jurassic.park.msu.ru, jannh@google.com, jcmvbkbc@gmail.com, jeffxu@chromium.org, jhubbard@nvidia.com, linux-alpha@vger.kernel.org, linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mips@vger.kernel.org, linux-mm@kvack.org, linux-parisc@vger.kernel.org, mattst88@gmail.com, muchun.song@linux.dev, paulmck@kernel.org, richard.henderson@linaro.org, shuah@kernel.org, sidhartha.kumar@oracle.com, surenb@google.com, tsbogend@alpha.franken.de, willy@infradead.org, elver@google.com, Linus Torvalds References: <87a5eysmj1.fsf@mid.deneb.enyo.de> <20241023062417.3862170-1-dvyukov@google.com> <8471d7b1-576b-41a6-91fb-1c9baae8c540@redhat.com> <5a3d3bc8-60db-46d0-b689-9aeabcdb8eab@lucifer.local> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Stat-Signature: 81g5h9uzbsmq6aibxtpent4rr9hguwnd X-Rspamd-Queue-Id: 8C404100011 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1729674375-817054 X-HE-Meta: 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 HB96Rz2A Y7ynB4SLiRaKIRkGZFRh05GGMICmYzy5aZ6Wvaen0ezVyUZM3FdTkZ4T2G0wHSvNFRd6C1xzQXhv5wZlf/hTSJh2A18T7CdyCftZGuf6Egd6lL2HSPODJSPY5U8zXGx/wMC34UepXTLhwFtx1aVdLfmtztw7nGhHJw2xJh2M6UiVRT3cD4Di2TZaw+we0VR7+MJSKD+y4voYus7X9PnR+woXSgkLNfZH65SQRHEJ/b68JIRIk+fhtUbQ4q2AnJ47SjjrtzW0xDNeUIshTNdW1ha7DgQDWeic14nrv X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, 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 10/23/24 10:56, Dmitry Vyukov wrote: >> >> Overall while I sympathise with this, it feels dangerous and a pretty major >> change, because there'll be something somewhere that will break because it >> expects faults to be swallowed that we no longer do swallow. >> >> So I'd say it'd be something we should defer, but of course it's a highly >> user-facing change so how easy that would be I don't know. >> >> But I definitely don't think a 'introduce the ability to do cheap PROT_NONE >> guards' series is the place to also fundmentally change how user access >> page faults are handled within the kernel :) > > Will delivering signals on kernel access be a backwards compatible > change? Or will we need a different API? MADV_GUARD_POISON_KERNEL? > It's just somewhat painful to detect/update all userspace if we add > this feature in future. Can we say signal delivery on kernel accesses > is unspecified? Would adding signal delivery to guard PTEs only help enough the ASAN etc usecase? Wouldn't it be instead possible to add some prctl to opt-in the whole ASANized process to deliver all existing segfaults as signals instead of -EFAULT ?