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Tue, 18 Feb 2025 16:48:07 +0000 (UTC) Date: Tue, 18 Feb 2025 17:48:00 +0100 From: Borislav Petkov To: Peter Zijlstra Cc: Shuai Xue , tony.luck@intel.com, nao.horiguchi@gmail.com, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, linmiaohe@huawei.com, akpm@linux-foundation.org, 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 v2 3/5] x86/mce: add EX_TYPE_EFAULT_REG as in-kernel recovery context to fix copy-from-user operations regression Message-ID: <20250218164800.GNZ7S5wL1A4dTaySOP@fat_crate.local> References: <20250217063335.22257-1-xueshuai@linux.alibaba.com> <20250217063335.22257-4-xueshuai@linux.alibaba.com> <20250218125408.GD40464@noisy.programming.kicks-ass.net> <1ff716d3-eb3d-477e-ae30-1abe97eee01b@linux.alibaba.com> <20250218141535.GC34567@noisy.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250218141535.GC34567@noisy.programming.kicks-ass.net> X-Rspam-User: X-Rspamd-Queue-Id: 1F0CBC000A X-Rspamd-Server: rspam12 X-Stat-Signature: 5rqiktbg8mc4c5tsabsbfgffj5wndexy X-HE-Tag: 1739897311-103873 X-HE-Meta: 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 jlANeQnw fpu+l0OItKvxHZ/gZTsQ3quFtPvC/7b6sOmLjEKWWL/S5+OO/LPTtroWlU+X+dqjuXkuNs7OQQOYXh+TahK/8zzKa6NFzxxzX4thTCi9E7DuNb9/rW6ehALcaqOgmgn/tQxgbEkV30BvOdoNvmFVvKnsgkEVo/cxEXMWda1IhQlJiLaNeXFZ70gUdvgp8UkL5vJAIphaM+wR6eXnlqbx0nqmOZeJXUByr6BQtN2NRrL8d0TKvWp93JgVZLbW2VqFwzOlSWziRNzERfahdpku9uXG+KKy8NXsQnQqUAiYEGQgukYlKcpbmPK0xptABin9FpMHx14JzcSMLoU//NGW6fGbVhXxgLhy89tpaxgnI2VNDcUDIOIj9x6Hfm8z7paFUv4yQGSIxRH+RR/w= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000066, 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 Tue, Feb 18, 2025 at 03:15:35PM +0100, Peter Zijlstra wrote: > diff --git a/arch/x86/kernel/cpu/mce/severity.c b/arch/x86/kernel/cpu/mce/severity.c > index dac4d64dfb2a..cfdae25eacd7 100644 > --- a/arch/x86/kernel/cpu/mce/severity.c > +++ b/arch/x86/kernel/cpu/mce/severity.c > @@ -301,18 +301,19 @@ static noinstr int error_context(struct mce *m, struct pt_regs *regs) > instrumentation_end(); > > switch (fixup_type) { > - case EX_TYPE_UACCESS: > - if (!copy_user) > - return IN_KERNEL; > - m->kflags |= MCE_IN_KERNEL_COPYIN; > - fallthrough; > - > case EX_TYPE_FAULT_MCE_SAFE: > case EX_TYPE_DEFAULT_MCE_SAFE: > m->kflags |= MCE_IN_KERNEL_RECOV; > return IN_KERNEL_RECOV; > > default: > + if (copy_user) { As said on chat, if we can make is_copy_from_user() *always* correctly detect user access, then sure but I'm afraid EX_TYPE_UACCESS being generated at the handful places where we do user memory access is there for a reason as it makes it pretty explicit. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette