[{"id":3684799,"web_url":"http://patchwork.ozlabs.org/comment/3684799/","msgid":"<3a981e61-67d4-45ee-8bb8-efce9c8849d0@linaro.org>","list_archive_url":null,"date":"2026-04-30T15:39:13","subject":"Re: [PATCH v2 1/2] tpm_emulator: Reject a buffer size larger than\n what was requested","submitter":{"id":85046,"url":"http://patchwork.ozlabs.org/api/people/85046/","name":"Philippe Mathieu-Daudé","email":"philmd@linaro.org"},"content":"On 30/4/26 16:23, Stefan Berger wrote:\n> When the TIS, SPAPR, or CRB frontends negotiate a buffer size with the\n> TPM backend, then the tpm_emulator (swtpm) could still adjust this size\n> of the buffer to within bounds supported by swtpm+libtpms if the chosen\n> size was outside the acceptable range. This could theoretically lead to\n> the TPM 2 using a bigger buffer than what was requested and memory\n> allocated for. In practice this would not happend since the requested size\n> of 4096 bytes for TIS and SPAPR and 3968 bytes for CRB are in the\n> (currently) supported range of ~2.5kb to 4096 bytes. With PQC support\n> the range will have an upper bound of 8kb and a lower bound that will\n> support the (pre-PQC) CRB with 3968 bytes.\n> \n> Signed-off-by: Stefan Berger \n> ---\n> backends/tpm/tpm_emulator.c | 13 ++++++++++++-\n> 1 file changed, 12 insertions(+), 1 deletion(-)\n\nReviewed-by: Philippe Mathieu-Daudé ","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=linaro.org header.i=@linaro.org header.a=rsa-sha256\n header.s=google header.b=Cld9uxyY;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; helo=lists1p.gnu.org;\n envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n receiver=patchwork.ozlabs.org)"],"Received":["from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17])\n\t(using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits))\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4g5yz41Lj1z1xqf\n\tfor ; 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charset=UTF-8; format=flowed","Content-Transfer-Encoding":"8bit","Received-SPF":"pass client-ip=2a00:1450:4864:20::334;\n envelope-from=philmd@linaro.org; helo=mail-wm1-x334.google.com","X-Spam_score_int":"-20","X-Spam_score":"-2.1","X-Spam_bar":"--","X-Spam_report":"(-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1,\n DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001,\n SPF_PASS=-0.001 autolearn=ham autolearn_force=no","X-Spam_action":"no action","X-BeenThere":"qemu-devel@nongnu.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"qemu development ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"}},{"id":3684816,"web_url":"http://patchwork.ozlabs.org/comment/3684816/","msgid":"","list_archive_url":null,"date":"2026-04-30T16:00:35","subject":"Re: [PATCH v2 1/2] tpm_emulator: Reject a buffer size larger than\n what was requested","submitter":{"id":75097,"url":"http://patchwork.ozlabs.org/api/people/75097/","name":"Stefan Berger","email":"stefanb@linux.ibm.com"},"content":"On 4/30/26 11:39 AM, Philippe Mathieu-Daudé wrote:\n> On 30/4/26 16:23, Stefan Berger wrote:\n>> When the TIS, SPAPR, or CRB frontends negotiate a buffer size with the\n>> TPM backend, then the tpm_emulator (swtpm) could still adjust this size\n>> of the buffer to within bounds supported by swtpm+libtpms if the chosen\n>> size was outside the acceptable range. This could theoretically lead to\n>> the TPM 2 using a bigger buffer than what was requested and memory\n>> allocated for. In practice this would not happend since the requested \n>> size\n>> of 4096 bytes for TIS and SPAPR and 3968 bytes for CRB are in the\n>> (currently) supported range of ~2.5kb to 4096 bytes. With PQC support\n>> the range will have an upper bound of 8kb and a lower bound that will\n>> support the (pre-PQC) CRB with 3968 bytes.\n>>\n>> Signed-off-by: Stefan Berger \n>> ---\n>>   backends/tpm/tpm_emulator.c | 13 ++++++++++++-\n>>   1 file changed, 12 insertions(+), 1 deletion(-)\n> \n> Reviewed-by: Philippe Mathieu-Daudé \n> \nThanks. I changed this also for v3 to require and exact match of buffer \nsizes.","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256\n header.s=pp1 header.b=V9U8uxwB;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; helo=lists1p.gnu.org;\n envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org;\n receiver=patchwork.ozlabs.org)"],"Received":["from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17])\n\t(using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits))\n\t(No client certificate requested)\n\tby legolas.ozlabs.org (Postfix) with ESMTPS id 4g5zTc2DHhz1yJr\n\tfor ; Fri, 01 May 2026 02:02:44 +1000 (AEST)","from localhost ([::1] helo=lists1p.gnu.org)\n\tby lists1p.gnu.org with esmtp (Exim 4.90_1)\n\t(envelope-from )\n\tid 1wITp1-0006Sa-5m; 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