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Fri, 21 Jun 2024 09:55:04 +0000 Received: from smtpav02.fra02v.mail.ibm.com (smtpav02.fra02v.mail.ibm.com [10.20.54.101]) by smtprelay04.fra02v.mail.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 45L9t0qT33161760 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 21 Jun 2024 09:55:02 GMT Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4BD942004B; Fri, 21 Jun 2024 09:55:00 +0000 (GMT) Received: from smtpav02.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1601320040; Fri, 21 Jun 2024 09:55:00 +0000 (GMT) Received: from funtu2.fritz.box?044ibm.com (unknown [9.171.71.218]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 21 Jun 2024 09:55:00 +0000 (GMT) From: Harald Freudenberger To: linux-crypto@vger.kernel.org Cc: herbert@gondor.apana.org.au, dengler@linux.ibm.com, Jason@zx2c4.com Subject: [PATCH] hwrng: core - Fix wrong quality calculation at hw rng registration Date: Fri, 21 Jun 2024 11:54:59 +0200 Message-Id: <20240621095459.43622-1-freude@linux.ibm.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: ab2EObRkaO9a6oMoLsPrLKurchizZbqG X-Proofpoint-GUID: ab2EObRkaO9a6oMoLsPrLKurchizZbqG X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.28.16 definitions=2024-06-21_03,2024-06-20_04,2024-05-17_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 clxscore=1011 suspectscore=0 lowpriorityscore=0 mlxscore=0 priorityscore=1501 impostorscore=0 adultscore=0 malwarescore=0 bulkscore=0 mlxlogscore=999 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2406140001 definitions=main-2406210069 When there are rng sources registering at the hwrng core via hwrng_register() a struct hwrng is delivered. There is a quality field in there which is used to decide which of the registered hw rng sources will be used by the hwrng core. With commit 16bdbae39428 ("hwrng: core - treat default_quality as a maximum and default to 1024") there came in a new default of 1024 in case this field is empty and all the known hw rng sources at that time had been reworked to not fill this field and thus use the default of 1024. The code choosing the 'better' hw rng source during registration of a new hw rng source has never been adapted to this and thus used 0 if the hw rng implementation does not fill the quality field. So when two rng sources register, one with 0 (meaning 1024) and the other one with 999, the 999 hw rng will be chosen. This patch simple takes into account that a quality field value of 0 is to be treated as 1024 and then the decision about which hw rng to use works as expected. Tested on s390 with two hardware rng sources: crypto cards and trng true random generator device driver. Signed-off-by: Harald Freudenberger Reported-by: Christian Rund Fixes: 16bdbae39428 ("hwrng: core - treat default_quality as a maximum and default to 1024") --- drivers/char/hw_random/core.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index 4084df65c9fa..993b8a1f1d19 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -525,6 +525,7 @@ static int hwrng_fillfn(void *unused) int hwrng_register(struct hwrng *rng) { + unsigned short rng_quality, cur_quality; int err = -EINVAL; struct hwrng *tmp; @@ -545,8 +546,14 @@ int hwrng_register(struct hwrng *rng) complete(&rng->cleanup_done); init_completion(&rng->dying); + /* Quality field not set in struct hwrng means 1024 */ + rng_quality = rng->quality ? rng->quality : 1024; + cur_quality = current_rng ? + (current_rng->quality ? current_rng->quality : 1024) : + 0; + if (!current_rng || - (!cur_rng_set_by_user && rng->quality > current_rng->quality)) { + (!cur_rng_set_by_user && rng_quality > cur_quality)) { /* * Set new rng as current as the new rng source * provides better entropy quality and was not