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dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:49316 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l7ePx-0001nO-0i for qemu-devel@archiver.kernel.org; Thu, 04 Feb 2021 08:11:29 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:38132) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l7eNy-0001Ac-JZ for qemu-devel@nongnu.org; Thu, 04 Feb 2021 08:09:26 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:33308) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l7eNw-0002Az-8g for qemu-devel@nongnu.org; Thu, 04 Feb 2021 08:09:26 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612444163; h=from:from: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:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=K5gynSwRjmnho0sxBnYutCxQDq1morUgdN/E6Th/OfQ=; b=WKuGBpCHlls5C+isr/MSJtFE+579B1D01xR22Ltcmpa6tD5HU+5c55Le12MMyjVRXofqr9 JKe49a9zvo0a2OsobPXrT7bd8s1CfB4QO1tJsaIMZ9ZbzbjNgqRt1NxpX5WMoga1QTxAuK GEZP13t3dAbxfyMgGX226LaWHvAenQA= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-284-YyIGRnVSM22E_j9Bxw9BdA-1; Thu, 04 Feb 2021 08:09:18 -0500 X-MC-Unique: YyIGRnVSM22E_j9Bxw9BdA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2E8681020C23; Thu, 4 Feb 2021 13:09:17 +0000 (UTC) Received: from thuth.remote.csb (ovpn-112-90.ams2.redhat.com [10.36.112.90]) by smtp.corp.redhat.com (Postfix) with ESMTP id CE4381001901; Thu, 4 Feb 2021 13:09:12 +0000 (UTC) Subject: Re: [PATCH] target/s390x/arch_dump: Fixes for the name field in the PT_NOTE section To: Christian Borntraeger , qemu-devel@nongnu.org, Cornelia Huck References: <20210203094454.260583-1-thuth@redhat.com> <1edf8bcd-3001-d459-3283-20e8ae2a3862@de.ibm.com> From: Thomas Huth Message-ID: <74e6c0a6-b08f-be1a-2e66-954982806576@redhat.com> Date: Thu, 4 Feb 2021 14:09:11 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <1edf8bcd-3001-d459-3283-20e8ae2a3862@de.ibm.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=thuth@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=thuth@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -32 X-Spam_score: -3.3 X-Spam_bar: --- X-Spam_report: (-3.3 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.351, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.182, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-s390x@nongnu.org, Richard Henderson , David Hildenbrand Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 04/02/2021 14.01, Christian Borntraeger wrote: > > > On 03.02.21 10:44, Thomas Huth wrote: >> According to the "ELF-64 Object File Format" specification: >> >> "The first word in the entry, namesz, identifies the length, in >> bytes, of a name identifying the entry’s owner or originator. The name field >> contains a null-terminated string, with padding as necessary to ensure 8- >> byte alignment for the descriptor field. The length does not include the >> terminating null or the padding." >> >> So we should not include the terminating NUL in the length field here. >> >> Also there is a compiler warning with GCC 9.3 when compiling with >> the -fsanitize=thread compiler flag: >> >> In function 'strncpy', >> inlined from 's390x_write_elf64_notes' at ../target/s390x/arch_dump.c:219:9: >> /usr/include/x86_64-linux-gnu/bits/string_fortified.h:106:10: error: >> '__builtin_strncpy' specified bound 8 equals destination size >> [-Werror=stringop-truncation] >> >> Since the name should always be NUL-terminated, we can simply decrease >> the size of the strncpy by one here to silence this warning. And while >> we're at it, also add an assert() to make sure that the provided names >> always fit the size field (which is fine for the current callers, the >> function is called once with "CORE" and once with "LINUX" as a name). >> >> Signed-off-by: Thomas Huth >> --- >> The ELF-64 spec can be found here, for example: >> https://uclibc.org/docs/elf-64-gen.pdf >> >> Here's a CI run with the compiler warning: >> https://gitlab.com/huth/qemu/-/jobs/1003508341#L1248 >> >> target/s390x/arch_dump.c | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/target/s390x/arch_dump.c b/target/s390x/arch_dump.c >> index 50fa0ae4b6..20c3a09707 100644 >> --- a/target/s390x/arch_dump.c >> +++ b/target/s390x/arch_dump.c >> @@ -212,11 +212,13 @@ static int s390x_write_elf64_notes(const char *note_name, >> int note_size; >> int ret = -1; >> >> + assert(strlen(note_name) < sizeof(note.name)); >> + >> for (nf = funcs; nf->note_contents_func; nf++) { >> memset(¬e, 0, sizeof(note)); >> - note.hdr.n_namesz = cpu_to_be32(strlen(note_name) + 1); >> + note.hdr.n_namesz = cpu_to_be32(strlen(note_name)); >> note.hdr.n_descsz = cpu_to_be32(nf->contents_size); >> - strncpy(note.name, note_name, sizeof(note.name)); >> + strncpy(note.name, note_name, sizeof(note.name) - 1); > > This kind of feels wrong. With 8 bytes of note.name, we should be able to store "Test123" + the final \0. > Now we tell strncpy to stop at 7. Which means that for Test123 we would NOT copy the final \0. Yes, but there is a memset(¬e, 0, sizeof(note)) at the beginning of the for-loop, so the 8th byte should always be set to 0 anyway. But if you prefer, I can also simply use g_strlcpy() instead...? Thomas