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Wed, 24 Jun 2026 15:10:42 +0000 (GMT) Received: from [9.224.77.173] (unknown [9.224.77.173]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 24 Jun 2026 15:10:42 +0000 (GMT) Message-ID: <72dabfe1-6302-4868-8351-c853a613ada6@linux.ibm.com> Date: Wed, 24 Jun 2026 17:10:42 +0200 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] s390/monwriter: Reject buffer reuse with different data length To: Gerald Schaefer , linux-s390 Cc: Heiko Carstens , Alexander Gordeev References: <20260623174406.189869-1-gerald.schaefer@linux.ibm.com> Content-Language: en-US From: Christian Borntraeger In-Reply-To: <20260623174406.189869-1-gerald.schaefer@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=X4Ni7mTe c=1 sm=1 tr=0 ts=6a3bf378 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=pFKB_4Q5YSifCqbc83YA:9 a=QEXdDO2ut3YA:10 a=zgiPjhLxNE0A:10 X-Proofpoint-Spam-Info: AW1haW4tMjYwNjI0MDEyMyBTYWx0ZWRfX+/XeNNKPlvBi iRbSkjF/SQ9+57GqfOmw/IZk6OVqATe9USPHgnVDrvCk/SR9xnV+XrkC9hW+gzibRMkqcScKuGK YNQGTe1zDxKfTWoir6ymFYW6lSfs56E= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjI0MDEyMyBTYWx0ZWRfX9kgnADp+hH/I ito4eUacygUh7YsKrONbZ71Q1snwBwlBSBh6JwvRWy0cr7M5nj39sRuEezvs3uAN6JQ43dz7EzH M1BAA2L68r90LAoYQQjRioj8KLvAgMsxgvxymIoCK/KWYSnM752Jp7SHlsB21GNpKIN5wX5G2To JAb14YV4d6RMpnSTLmhHAoCZqsIIwxNsl/IItNSgac0ISFkPagCOWnSllBhtKQrTAhX1WsM9KCP 0zaj9+CBoEi3L319JTn4d1+GIMUPaGmfb6dOaOAkzn+qEgxhKvuCDOrTCiHYAsywUkVSrUOphRn 7dBfLERFCL5m6ZIdsEIi0SEFXMDJupHhc4rTnkmBDHnHXt+HqkXN2VRfTA5hQAUE1GVVzL7lEa1 cVe6rVCAq2c8kO9LKyfzj1tttip/VA== X-Proofpoint-ORIG-GUID: 6pMjIZ5I2_FUXQqcdnDbbrrkCKkMTbMp X-Proofpoint-GUID: 6pMjIZ5I2_FUXQqcdnDbbrrkCKkMTbMp 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=2026-06-24_03,2026-06-24_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 phishscore=0 suspectscore=0 spamscore=0 malwarescore=0 adultscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606240123 Am 23.06.26 um 19:44 schrieb Gerald Schaefer: > When data buffers are reused, e.g. for interval sample records, the > first record determines the data length, and the size of the buffer for > user copy. Current monwriter code does not check if the data length was > changed for subsequent records, which also would never happen for valid > user programs. > > However, a malicious user could change the data length, resulting in out > of bounds user copy to the kernel buffer, and memory corruption. By > default, the monwriter misc device is created with root-only permissions, > so practical impact is typically low. > > Fix this by checking for changed data length and rejecting such records. > > Cc: stable@vger.kernel.org > Signed-off-by: Gerald Schaefer Reviewed-by: Christian Borntraeger