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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Tue, 18 Jun 2019 14:55:36 +0100 Received: from b06wcsmtp001.portsmouth.uk.ibm.com (b06wcsmtp001.portsmouth.uk.ibm.com [9.149.105.160]) by b06cxnps4074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x5IDtaKP49086586 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 18 Jun 2019 13:55:36 GMT Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E8B35A4054; Tue, 18 Jun 2019 13:55:35 +0000 (GMT) Received: from b06wcsmtp001.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id F244DA405B; Tue, 18 Jun 2019 13:55:34 +0000 (GMT) Received: from dhcp-9-31-103-88.watson.ibm.com (unknown [9.31.103.88]) by b06wcsmtp001.portsmouth.uk.ibm.com (Postfix) with ESMTP; Tue, 18 Jun 2019 13:55:34 +0000 (GMT) Subject: Re: [PATCH] ima: dynamically allocate shash_desc From: Mimi Zohar To: Arnd Bergmann Cc: Dmitry Kasatkin , James Morris , "Serge E. Hallyn" , Jarkko Sakkinen , Stefan Berger , linux-integrity@vger.kernel.org, LSM List , Linux Kernel Mailing List In-Reply-To: References: <20190617115838.2397872-1-arnd@arndb.de> <1560786951.4072.103.camel@linux.ibm.com> <1560794826.4072.169.camel@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" Date: Tue, 18 Jun 2019 08:44:38 -0400 Mime-Version: 1.0 X-Mailer: Evolution 3.20.5 (3.20.5-1.fc24) Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19061813-0008-0000-0000-000002F4CB64 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19061813-0009-0000-0000-00002261E300 Message-Id: <1560861878.9530.17.camel@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-18_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=3 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906180113 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2019-06-17 at 22:08 +0200, Arnd Bergmann wrote: > On Mon, Jun 17, 2019 at 8:08 PM Mimi Zohar wrote: > > > > On Mon, 2019-06-17 at 11:55 -0400, Mimi Zohar wrote: > > > On Mon, 2019-06-17 at 13:20 +0200, Arnd Bergmann wrote: > > > > On 32-bit ARM, we get a warning about excessive stack usage when > > > > building with clang. > > > > > > > > security/integrity/ima/ima_crypto.c:504:5: error: stack frame size > > > > of 1152 bytes in function 'ima_calc_field_array_hash' [-Werror,- > > > > Wframe-larger-than=] > > > > > > I'm definitely not seeing this. Is this problem a result of non > > > upstreamed patches? For sha1, currently the only possible hash > > > algorithm, I'm seeing 664. > > You won't see it with gcc, only with clang in some randconfig builds, > I suppose only when KASAN is enabled. > > > Every time a measurement is added to the measurement list, the memory > > would be allocated/freed. The frequency of new measurements is policy > > dependent. For performance reasons, I'd prefer if the allocation > > remains on the stack. > > Is there a way to preallocate the shash_desc instead? That would > avoid the overhead. There are 3 other SHASH_DESC_ON_STACK definitions in just ima_crypto.c, with a total of ~55 other places in the kernel.  Before fixing this particular function, I'd like to know if the "excessive stack usage" warning is limited to ima_calc_field_array_hash_tfm().  If so, what is so special about its usage of SHASH_DESC_ON_STACK? thanks, Mimi