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[209.85.208.49]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ae053ee4bfdsm571906966b.65.2025.06.22.10.04.52 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 22 Jun 2025 10:04:52 -0700 (PDT) Received: by mail-ed1-f49.google.com with SMTP id 4fb4d7f45d1cf-607ea238c37so6780495a12.2 for ; Sun, 22 Jun 2025 10:04:52 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCX8IhM0nR9yLMajT7KILxLB2zkaZRj1RIwQ3KoDpGQ5PlLGGzkk8YMGcMONUJREpRY2jWdoOa9jQQ==@kvack.org X-Received: by 2002:a05:6402:1e90:b0:608:3571:6942 with SMTP id 4fb4d7f45d1cf-60a1cca9d65mr7384121a12.1.1750611456313; Sun, 22 Jun 2025 09:57:36 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Linus Torvalds Date: Sun, 22 Jun 2025 09:57:20 -0700 X-Gmail-Original-Message-ID: X-Gm-Features: AX0GCFts7S7trAg95_9iRhGDGkpXCnUtzlq1LLaD_2GFvkl-rWcgRNFXTCHwODg Message-ID: Subject: Re: [PATCH 2/5] uaccess: Add speculation barrier to copy_from_user_iter() To: Christophe Leroy Cc: Michael Ellerman , Nicholas Piggin , Naveen N Rao , Madhavan Srinivasan , Alexander Viro , Christian Brauner , Jan Kara , Thomas Gleixner , Ingo Molnar , Peter Zijlstra , Darren Hart , Davidlohr Bueso , Andre Almeida , Andrew Morton , David Laight , Dave Hansen , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Queue-Id: 07D2D40008 X-Rspamd-Server: rspam10 X-Stat-Signature: 9975wkbbups9khemm3o8n9xj6561dwub X-HE-Tag: 1750611894-68879 X-HE-Meta: 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 +UnOulmr 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 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 Sun, 22 Jun 2025 at 02:52, Christophe Leroy wrote: > > The results of "access_ok()" can be mis-speculated. Hmm. This code is critical. I think it should be converted to use that masked address thing if we have to add it here. And at some point this access_ok() didn't even exist, because we check the addresses at iter creation time. So this one might be a "belt and suspenders" check, rather than something critical. (Although I also suspect that when we added ITER_UBUF we might have created cases where those user addresses aren't checked at iter creation time any more). Linus