From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45931) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eQGTj-000635-Cy for qemu-devel@nongnu.org; Sat, 16 Dec 2017 12:42:30 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eQGTf-0008UX-C3 for qemu-devel@nongnu.org; Sat, 16 Dec 2017 12:42:27 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:45830 helo=mx0a-001b2d01.pphosted.com) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eQGTf-0008Ty-63 for qemu-devel@nongnu.org; Sat, 16 Dec 2017 12:42:23 -0500 Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id vBGHdUdn134491 for ; Sat, 16 Dec 2017 12:42:22 -0500 Received: from e37.co.us.ibm.com (e37.co.us.ibm.com [32.97.110.158]) by mx0b-001b2d01.pphosted.com with ESMTP id 2ew0h5k70f-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Sat, 16 Dec 2017 12:42:22 -0500 Received: from localhost by e37.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sat, 16 Dec 2017 10:42:21 -0700 From: Stefan Berger Date: Sat, 16 Dec 2017 12:41:32 -0500 In-Reply-To: <1513446109-9013-1-git-send-email-stefanb@linux.vnet.ibm.com> References: <1513446109-9013-1-git-send-email-stefanb@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Message-Id: <1513446109-9013-16-git-send-email-stefanb@linux.vnet.ibm.com> Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] [PULL v1 15/32] tpm-passthrough: workaround a possible race List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: peter.maydell@linaro.org, =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= , Stefan Berger From: Marc-Andr=C3=A9 Lureau The TPM backend processing thread has common shared variable race issues. (they should not be so easy to reach since guest interaction with the device is slow compared to host emulation) An obvious one is setting op_cancelled from device thread after calling write(cancel_fd). The backend thread may return before the device thread has set the variable. Instead set it before cancellation. Even if the write() failed, the end result is command get possibly cancelled (even if cancellation came from external sources it doesn't matter much). It's worth to consider removing the backend processing thread for now. Signed-off-by: Marc-Andr=C3=A9 Lureau Reviewed-by: Stefan Berger Signed-off-by: Stefan Berger --- hw/tpm/tpm_passthrough.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/hw/tpm/tpm_passthrough.c b/hw/tpm/tpm_passthrough.c index 788be38..73554aa 100644 --- a/hw/tpm/tpm_passthrough.c +++ b/hw/tpm/tpm_passthrough.c @@ -89,6 +89,7 @@ static int tpm_passthrough_unix_tx_bufs(TPMPassthruStat= e *tpm_pt, bool is_selftest; const struct tpm_resp_hdr *hdr; =20 + /* FIXME: protect shared variables or use other sync mechanism */ tpm_pt->tpm_op_canceled =3D false; tpm_pt->tpm_executing =3D true; *selftest_done =3D false; @@ -178,12 +179,11 @@ static void tpm_passthrough_cancel_cmd(TPMBackend *= tb) */ if (tpm_pt->tpm_executing) { if (tpm_pt->cancel_fd >=3D 0) { + tpm_pt->tpm_op_canceled =3D true; n =3D write(tpm_pt->cancel_fd, "-", 1); if (n !=3D 1) { error_report("Canceling TPM command failed: %s", strerror(errno)); - } else { - tpm_pt->tpm_op_canceled =3D true; } } else { error_report("Cannot cancel TPM command due to missing " --=20 2.5.5