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Mon, 22 Jun 2026 16:18:22 +0000 (GMT) Received: from [9.87.145.196] (unknown [9.87.145.196]) by smtpav03.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 22 Jun 2026 16:18:21 +0000 (GMT) Message-ID: Date: Mon, 22 Jun 2026 18:18:21 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 2/9] KVM: s390: Fix dat_peek_cmma() overflow To: Claudio Imbrenda , linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, frankja@linux.ibm.com, david@kernel.org, seiden@linux.ibm.com, nrb@linux.ibm.com, schlameuss@linux.ibm.com, gra@linux.ibm.com, hca@linux.ibm.com, gerald.schaefer@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, svens@linux.ibm.com References: <20260622160739.202044-1-imbrenda@linux.ibm.com> <20260622160739.202044-3-imbrenda@linux.ibm.com> Content-Language: en-US From: Christian Borntraeger In-Reply-To: <20260622160739.202044-3-imbrenda@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 2y3nYnI_S6vGiEZsmIl3wqM5NsMzc2XU X-Proofpoint-Spam-Info: AW1haW4tMjYwNjIyMDE2MCBTYWx0ZWRfXxrP4UkzagjPS 2FQ3awCZdthN7p1n/DauZwZSzQczX7NkiTtW6Zm+sU0yFZ8vOChK/q6CaZb0Tlduk6WAAKA2FlE 1i9KcJLsmdxOWLNHLL0hH/qCIfrrYAA= X-Authority-Analysis: v=2.4 cv=c62bhx9l c=1 sm=1 tr=0 ts=6a396053 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=V7Lfsfyam54kdkz9vnAA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjIyMDE2MCBTYWx0ZWRfX5k0nMjeP71rM JNIcea/MYUYEJ53D29JULA03wElTHmWdF2wx8jLomnv3qO7/VxbsM2rYyIppegks1pTKenGKiQf Jd1JcPkWsM37wU9y879eNKDvZFMhNAgKDG1+ZDG/7AkRifCRAqMtxBZ2yU64bAHP7u8e4CmTxSR jFplu6eIYXWw+rEcsvi0SrRD+YtqOxcomIym528bhhD6xaXyhTCGBS8HN60kMW8ioj4ml75MxP3 Y8dGDFRooNACM+f3DjnIkNDXTKScU3h7V3fYTUSWwiyxtcLs6RWQLwwFXtI4yy2jQRmsHkDdIj0 ErM5ByZJzNbzAjF3x0GuDaaaqQL1MuQuQF0O7DjdU4xO9fFuYnTo9Bmk8qaPJlr24gH5HwsbMdE Sp3wuQpuayzeqJi5HB0Q8Dx6Xd2P7Wjl+5eywArdP2IDrQP/u9bGDGd19Ausl9r7AYMiZFYUpEs 8u1zqbI5jNhPqW00VMw== X-Proofpoint-ORIG-GUID: 2y3nYnI_S6vGiEZsmIl3wqM5NsMzc2XU X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-22_03,2026-06-22_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 impostorscore=0 adultscore=0 clxscore=1015 suspectscore=0 priorityscore=1501 phishscore=0 spamscore=0 bulkscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606220160 Am 22.06.26 um 18:07 schrieb Claudio Imbrenda: > If userspace passes a start address that is out of bounds, > _dat_walk_gfn_range() will fail with -EFAULT, but state.end will not be > touched and will stay 0. This will cause *count to underflow and report > a very high number, and the function will end up erroneously reporting > success. > > Fix by only setting *count if the end address is not smaller than the > starting address. This way invalid starting addresses will correctly > return -EFAULT and *count will correctly indicate that no values have > been returned. > > Fixes: 7b368470e1a4 ("KVM: s390: KVM page table management functions: CMMA") > Signed-off-by: Claudio Imbrenda Reviewed-by: Christian Borntraeger > --- > arch/s390/kvm/dat.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/s390/kvm/dat.c b/arch/s390/kvm/dat.c > index 4a41c0247ffa..cffac7782c4b 100644 > --- a/arch/s390/kvm/dat.c > +++ b/arch/s390/kvm/dat.c > @@ -1209,7 +1209,7 @@ int dat_peek_cmma(gfn_t start, union asce asce, unsigned int *count, u8 *values) > int rc; > > rc = _dat_walk_gfn_range(start, start + *count, asce, &ops, DAT_WALK_DEFAULT, &state); > - *count = state.end - start; > + *count = state.end >= start ? state.end - start : 0; > /* Return success if at least one value was saved, otherwise an error. */ > return (rc == -EFAULT && *count > 0) ? 0 : rc; > }