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Fri, 7 Mar 2025 20:40:23 +0000 (UTC) Date: Fri, 7 Mar 2025 21:40:18 +0100 From: Borislav Petkov To: Shuai Xue Cc: tony.luck@intel.com, peterz@infradead.org, catalin.marinas@arm.com, yazen.ghannam@amd.com, akpm@linux-foundation.org, linmiaohe@huawei.com, nao.horiguchi@gmail.com, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, jpoimboe@kernel.org, linux-edac@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, baolin.wang@linux.alibaba.com, tianruidong@linux.alibaba.com Subject: Re: [PATCH v4 1/3] x86/mce: Use is_copy_from_user() to determine copy-from-user context Message-ID: <20250307204018.GAZ8tZstt11Y4KFprC@fat_crate.local> References: <20250307054404.73877-1-xueshuai@linux.alibaba.com> <20250307054404.73877-2-xueshuai@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250307054404.73877-2-xueshuai@linux.alibaba.com> X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 13480C000A X-Stat-Signature: fir4qrh6wdzbg5yqfgpeoe8y4kwze6xa X-Rspam-User: X-HE-Tag: 1741380065-241945 X-HE-Meta: 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 eyhUwyKQ U12fg39zaFixz6y9XHQzpUznFqmqHgBE0L7SQZA5BVbk8KzSS4DZdEENHYY/XSfPVS+43Gm0UZAEveB7UDk9hzuKCUwpsMj0zpcf0OkMcw5Ibqeok8f27xVJhGdiph2nK9caDqyQFLxQTQW1sd/N7qTkQjQ91je6sqkeinNaIpxq96js3qNoZ/0LbVJbBzUVsjrc04QIyKK4FlCP2WTqp96C3rcFqwMTmzUMPsYpcmr40ce7mKfner6av+b/dQ08nYIFhhJEBbYAPYxTSFEXjrdrHqud7qZhhnXrkawze0Mvm2pZzCdYuYK+TN+gygBLZg6uItXpx1s59Ni5QybwfGaWejGDNyqhs/Yu5rns5p4jEjU9+d7/Pw3/rp4fPZkHohXa0HikFo7c+ezA= X-Bogosity: Ham, tests=bogofilter, spamicity=0.053123, 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 Fri, Mar 07, 2025 at 01:44:02PM +0800, Shuai Xue wrote: > Commit 4c132d1d844a ("x86/futex: Remove .fixup usage") introduced a new > extable fixup type, EX_TYPE_EFAULT_REG, and commit 4c132d1d844a > ("x86/futex: Remove .fixup usage") updated the extable fixup type for > copy-from-user operations, changing it from EX_TYPE_UACCESS to > EX_TYPE_EFAULT_REG. The error context for copy-from-user operations no > longer functions as an in-kernel recovery context. Consequently, the error > context for copy-from-user operations no longer functions as an in-kernel > recovery context, resulting in kernel panics with the message: "Machine > check: Data load in unrecoverable area of kernel." > > The critical aspect is identifying whether the error context involves a > read from user memory. We do not care about the ex-type if we know its a Please use passive voice in your commit message: no "we" or "I", etc, and describe your changes in imperative mood. Also, pls read section "2) Describe your changes" in Documentation/process/submitting-patches.rst for more details. Also, see section "Changelog" in Documentation/process/maintainer-tip.rst Bottom line is: personal pronouns are ambiguous in text, especially with so many parties/companies/etc developing the kernel so let's avoid them please. "ex-type"? Please write in plain English - not in a programming language. > MOV reading from userspace. is_copy_from_user() return true when both of > the following conditions are met: > > - the current instruction is copy There is no "copy instruction". You mean the "current operation". > - source address is user memory So you can simply say "when reading user memory". Simple. > > So, use is_copy_from_user() to determin if a context is copy user directly. Unknown word [determin] in commit message. Suggestions: ['determine', Please introduce a spellchecker into your patch creation workflow. Also, run your commit messages through AI to correct the grammar and formulations in them. The more important part which I asked for already is, is is_copy_from_user() exhaustive in determining the that the operation really is a copy from user? The EX_TYPE_UACCESS things *explicitly* marked such places in the code. Does is_copy_from_user() guarantee the same, without false positives? -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette