From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 18CDDC433E1 for ; Fri, 21 Aug 2020 09:48:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E066720732 for ; Fri, 21 Aug 2020 09:48:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="osVGyMuE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728423AbgHUJs1 (ORCPT ); Fri, 21 Aug 2020 05:48:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57066 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725855AbgHUJsZ (ORCPT ); Fri, 21 Aug 2020 05:48:25 -0400 Received: from mail-pl1-x641.google.com (mail-pl1-x641.google.com [IPv6:2607:f8b0:4864:20::641]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B53B3C061385; Fri, 21 Aug 2020 02:48:25 -0700 (PDT) Received: by mail-pl1-x641.google.com with SMTP id k13so628829plk.13; Fri, 21 Aug 2020 02:48:25 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=n0gxWhKy8HZT9XqQrHP7qU76kr+KPT1ex9umU9pXHWE=; b=osVGyMuEzo2+GKkTLQba7FeGgYH958kaGau2qYDDBI/XvHwKz+hfv3Kb9gLOEYFuQ9 Oy5LbYuAwZPVMpeTVtFsG1gIANz5vXPHJApamEGGDFIRhYz+x3bw8yyETS6pccCUtREM p0evb7r3GCK2wbmUo3N1e5b4w0v5ZETiUq64KFOdIHutXsMheDKwQxwxKvhnatFuc5Zk vLMmt0oKZU6E5DfJVNTLAU49zdiYnvpSpXFhwXVvVpscce9JiSUpXv/yLaoNkcV8CK/I 9sJO0srddWK35YRu6gC4W2ZZ+7xwnqR6H/xon3v6ix37Ckm6PHwki17PZ9PUfrC3iGgS bJsw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=n0gxWhKy8HZT9XqQrHP7qU76kr+KPT1ex9umU9pXHWE=; b=Rk5FU0H7jV+Lg2nAPj4R0bc1k0mrDRUMwZb1qRgVV5LvhJNLNG43itZgen5E9iKeNC 2V/lpsdriCuyZYouZq+c44bTggzKfVKEbalZDCq+13XDmyunVp6hcP7TCPrSYYj0Cx67 /XTb6ZblicGxZeKC/wNZp+GOsJGuv7b8Pxm9u5x/nYhd6bc5O5MGJQDDfpa5+tEfLj9B OyN90BZ3bdboBLCVjOnekQu21vJ/vSaUmFLq1XJU5Ddd1IKyrEa1fRyTdVRiLqCXNqFe nHPMRldNq28nu5U7hl3qPDVdHhALwT1gMObJJKsGeImqaz0SlB20fsk0S0ivzgYoCVHO QqIg== X-Gm-Message-State: AOAM532LSl4RcRejr0Y2QzUie6zniTMwBRg++ND5BPE9cLKsEgcJQO3J Bd6G8pwT8xXC0OgfcrIS+uTRy2Ouas16 X-Google-Smtp-Source: ABdhPJzPxMw/GkVtaa/3YcwQtpvwf805RqnVAiPPLRe6mxdBj+kjewtcCTKhpqRRxLQIzXrDRdfaQw== X-Received: by 2002:a17:90a:17a7:: with SMTP id q36mr1856454pja.61.1598003305256; Fri, 21 Aug 2020 02:48:25 -0700 (PDT) Received: from PWN ([2600:3c01::f03c:91ff:fe6e:64cd]) by smtp.gmail.com with ESMTPSA id u29sm1993493pfl.180.2020.08.21.02.48.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Aug 2020 02:48:24 -0700 (PDT) Date: Fri, 21 Aug 2020 05:48:13 -0400 From: Peilin Ye To: Hans Verkuil Cc: Greg Kroah-Hartman , linux-media@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, syzkaller-bugs@googlegroups.com, linux-kernel@vger.kernel.org Subject: Re: [Linux-kernel-mentees] [PATCH] v4l2-tpg: Fix global-out-of-bounds read in precalculate_color() Message-ID: <20200821094813.GB480216@PWN> References: <20200810050532.640075-1-yepeilin.cs@gmail.com> <774bcf2d-c8eb-086a-3569-c7e530d8a63d@xs4all.nl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <774bcf2d-c8eb-086a-3569-c7e530d8a63d@xs4all.nl> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mr. Verkuil, On Wed, Aug 19, 2020 at 04:26:28PM +0200, Hans Verkuil wrote: > Hi Peilin, > > On 10/08/2020 07:05, Peilin Ye wrote: > > precalculate_color() is reading out of `sin` since `tpg->hue` is not being > > properly checked. Fix it. `cos` is safe, as long as `tpg->hue` is higher > > than or equal to -192. > > Thank you for this patch, but there is something I don't understand, namely > just *how* tpg->hue can be out-of-range. > > From what I can see vivid sets hue via tpg_s_hue() when the V4L2_CID_HUE control > is set. But that control has a range of -128...128, so ctrl->val should always be in > that range. > > I would really like to know 1) what the value of tpg->hue actually is when it goes > out of range, and 2) who is changing it to that value. Can you do a bit more digging? The value of `tpg->hue` was -20551. It came from the userspace, see the "\xb9\xaf" on line 500 of the reproducer: https://syzkaller.appspot.com/text?tag=ReproC&x=14b49e71e00000 NONFAILING(memcpy((void*)0x20000200, "/dev/video6\000\000", 13)); res = syscall(__NR_openat, 0xffffffffffffff9cul, 0x20000200ul, 2ul, 0ul); if (res != -1) r[0] = res; NONFAILING(memcpy((void*)0x20000140, "\x4d\x43\x66\x34\xfd\x89\xb9\xaf\x0d\x59\xa2\x83\x4c\xfd" ^^^^ ^^^^ ^^^^ ^^^^^^^^ "\x3e\x64\x7c\x96\xcd\x59\xf2\x3a\x18\xa3\x81\x49\x22\xc0" "\xc1\xbf\x02\xa5\x50\x5f\xcb\x48\x92\x0e\xf3\xdc\xff\x85" "\xb7\x84\x21\xab\xef\x31\x3d\xb1\xb6\x5d\xbf\x07\x8e\xee" "\x5e\x7c\x73\x32\xf4\x9d\x1e\x62\x6b\x6a\xa0\x74\x73\xe6" "\xca\x1b\xdb\x7a\xca\x76\xd8\x37\xb8\xd9", 80)); syscall(__NR_write, r[0], 0x20000140ul, 8ul); I guess the root cause is a race condition in the vivid test driver, which completely corrupted `tpg`. I see bytes like "\x4d", "\x66" and "\xfd" around `tpg->hue`, too. The reproducer does two things: the above write() on /dev/video6, and a preadv() on /dev/video3: NONFAILING(*(uint64_t*)0x20000800 = 0x20000000); NONFAILING(*(uint64_t*)0x20000808 = 0x1f); NONFAILING(*(uint64_t*)0x20000810 = 0); NONFAILING(*(uint64_t*)0x20000818 = 0); NONFAILING(*(uint64_t*)0x20000820 = 0); NONFAILING(*(uint64_t*)0x20000828 = 0); NONFAILING(*(uint64_t*)0x20000830 = 0); NONFAILING(*(uint64_t*)0x20000838 = 0); NONFAILING(*(uint64_t*)0x20000840 = 0); NONFAILING(*(uint64_t*)0x20000848 = 0); syscall(__NR_preadv, r[1], 0x20000800ul, 5ul, 0ul); I commented out this preadv(), then the reproducer didn't cause any crash. Unfortunately I don't know the code well enough in order to figure out exactly why...At this point of time I'd like to send you an v2 as you suggested, it should work as a mitigation. Thank you for the suggestion! Peilin Ye