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[80.230.85.71]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4601f344762sm84495116f8f.23.2026.06.11.03.42.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Jun 2026 03:42:59 -0700 (PDT) Date: Thu, 11 Jun 2026 06:42:56 -0400 From: "Michael S. Tsirkin" To: Herbert Xu Cc: Michael Bommarito , Olivia Mackall , linux-crypto@vger.kernel.org, Jason Wang , Kees Cook , Christian Borntraeger , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, Dan Williams , Ingo Molnar , "H. Peter Anvin" , torvalds@linux-foundation.org, alan@linux.intel.com, tglx@linutronix.de Subject: Re: [PATCH v3] hwrng: virtio: clamp device-reported used.len at copy_data() Message-ID: <20260611064040-mutt-send-email-mst@kernel.org> References: <20260531142251.2792061-1-michael.bommarito@gmail.com> <20260611025916-mutt-send-email-mst@kernel.org> <20260611035035-mutt-send-email-mst@kernel.org> <20260611050731-mutt-send-email-mst@kernel.org> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 81RujCALRRovdeSxALJp9Y5zc7rsNQR9w28B70PJcGQ_1781174581 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Jun 11, 2026 at 05:19:26PM +0800, Herbert Xu wrote: > On Thu, Jun 11, 2026 at 05:10:32AM -0400, Michael S. Tsirkin wrote: > > > > data_avail is under hypervisor control > > > > avail = min_t(unsigned int, vi->data_avail, sizeof(vi->data)); > > if (vi->data_idx >= avail) { > > vi->data_idx = 0; > > > > and maybe this can speculate past the if? > > > > I agree, this is all speculation ) > > Either it is vulnerable to Spectre, or it isn't. Adding nospec > markers when you're not sure is cargo cult programming. AKA defence is depth programming) Alright we can drop this. No biggie. -- MST