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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id w14-20020a17090aea0e00b00200558540a3sm1596538pjy.53.2022.09.16.08.09.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Sep 2022 08:09:17 -0700 (PDT) Date: Fri, 16 Sep 2022 08:09:16 -0700 From: Kees Cook To: Matthew Wilcox Cc: Uladzislau Rezki , Andrew Morton , Yu Zhao , dev@der-flo.net, linux-mm@kvack.org, linux-hardening@vger.kernel.org, Peter Zijlstra , Ingo Molnar , linux-kernel@vger.kernel.org, x86@kernel.org, linux-perf-users@vger.kernel.org, linux-arch@vger.kernel.org Subject: Re: [PATCH 3/3] usercopy: Add find_vmap_area_try() to avoid deadlocks Message-ID: <202209160805.CA47B2D673@keescook> References: <20220916135953.1320601-1-keescook@chromium.org> <20220916135953.1320601-4-keescook@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=Gq1QrMj4; spf=pass (imf15.hostedemail.com: domain of keescook@chromium.org designates 209.85.215.169 as permitted sender) smtp.mailfrom=keescook@chromium.org; dmarc=pass (policy=none) header.from=chromium.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1663340960; a=rsa-sha256; cv=none; b=w7mHmy4cV9H5Uk+w6FD/egt5DIoQH4ap25AfEddXmUiP5UaYV1QXzR8nZIeIdatO3pKe04 X4b9WVAt3wRee9wwnWrf3ZtuPyXOPe/Gixy1Ai8YC9uWVZ89WCyOlHN0HO75ak1JExtJ6x bW2hY33JzJmxjKwbEuhJKLJ1Br1f850= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1663340960; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=4R00t3D0GnXDRz5F9l2Kk2rqoyZp2jq6sAMUbdTmoVQ=; b=hytxHmRS5BAgFAtZL84KseyahDh1WErWYqYiB8C32MhcAKAGgwwH4siqmKtPSWNKlCQm68 UAFz0nW7W3ALe0RDj3iJi9RQge5+R6drxC+Yl3oLKY/SsxRWz3P/Wh5PMULE5DBb5lBT1J Sg/9r2mHZYR8HPQ9KzEJnGORfqBREJE= X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 09003A00B5 Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=chromium.org header.s=google header.b=Gq1QrMj4; spf=pass (imf15.hostedemail.com: domain of keescook@chromium.org designates 209.85.215.169 as permitted sender) smtp.mailfrom=keescook@chromium.org; dmarc=pass (policy=none) header.from=chromium.org X-Stat-Signature: hxwifzqa3xmdrpcw4u8ojqaknzyhr4g8 X-HE-Tag: 1663340959-19724 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: On Fri, Sep 16, 2022 at 03:46:07PM +0100, Matthew Wilcox wrote: > On Fri, Sep 16, 2022 at 06:59:57AM -0700, Kees Cook wrote: > > The check_object_size() checks under CONFIG_HARDENED_USERCOPY need to be > > more defensive against running from interrupt context. Use a best-effort > > check for VMAP areas when running in interrupt context > > I had something more like this in mind: Yeah, I like -EAGAIN. I'd like to keep the interrupt test to choose lock vs trylock, otherwise it's trivial to bypass the hardening test by having all the other CPUs beating on the spinlock. Thanks! -Kees -- Kees Cook