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Thu, 3 Sep 2026 13:07:34 +0000 (GMT) Received: from tuxmaker.boeblingen.de.ibm.com (unknown [9.87.85.9]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 3 Sep 2026 13:07:33 +0000 (GMT) From: Mikhail Zaslonko To: linux-s390@vger.kernel.org Cc: Heiko Carstens , Alexander Gordeev , Vasily Gorbik , Ilya Leoshkevich , Peter Oberparleiter Subject: [PATCH v3 0/3] s390/debug: Fix several s390dbf issues reported by AI scan Date: Thu, 3 Sep 2026 15:07:30 +0200 Message-ID: <20260903130733.709001-1-zaslonko@linux.ibm.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: ZV2zfFUtNQC8MJdR0HExcCeel-JAaZrC X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTAzMDExMyBTYWx0ZWRfX0AJS8hJKJmpm 2WJvugak+64vJx/O6xKe5sLeVtEDtlrlIecq22k0y4BQthBOuWT/EoPUJYkNU03sFMoQv57mvZB SG13IjUWAzH2OIJ7n6lwUdGXb/xVRShN/NxVNhbcTPcXOJHkUdwSkTw7cz86Vt5CclM4B1Kz3b/ nLMhCbpw0jUjOBL2b53L6VuDF6QvxBNTCcXUsbOsABle0sdvFZoIDhev8Ph33hlxxw+dFtETUYz /cgwE093J9Iz5YiqPFBykltrB22KCxl0jYT6iNTeSj6SQbOi9fAeY/IHFapO5xwXRdhIzNFF4IC yRwvj8iDlcz7+o7ryxQ/faH3E1wgOjMTefC0WhPbuMnd8Zec/vxpdBtLmeOM2DdcVKc5w7LURTK QHk0pDmuM+Z8B3EUB/N/k+9zFwx498qY3zEZ9QKDH8+B/arlA0UJawOn4jSYu4kAFGUINrLO3yC 4XplxCTHuxgmDK4r+3Q== X-Authority-Analysis: v=2.4 cv=Osl/DS/t c=1 sm=1 tr=0 ts=6a99711b cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=dRcrNZYWpG77ggIxQPMA:9 X-Proofpoint-Spam-Info: AW1haW4tMjYwOTAzMDExMyBTYWx0ZWRfX/tE39BcrxnCq bYzpNxOXg+guC0nMoghx0UhjxvtDks846EcJoXF5FJPuTSfhrCqLgY5I5xZw4W9Rum9NI/xfS5Y wKQBzT/Llzm0gb3M7A2+8tL1qV7xDL0= X-Proofpoint-ORIG-GUID: ZV2zfFUtNQC8MJdR0HExcCeel-JAaZrC X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-03_03,2026-09-03_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 malwarescore=0 suspectscore=0 bulkscore=0 lowpriorityscore=0 adultscore=0 impostorscore=0 phishscore=0 clxscore=1015 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2609030113 The s390dbf kernel parameter was added in commit a2cec6863709 ("s390/debug: Add s390dbf kernel parameter"). This series fixes three issues found in the surrounding code. Patch 1 fixes a NULL pointer dereference in debug_set_level() introduced by that commit: the NULL check for the id argument was moved into the _debug_set_level() helper, but the newly added debug_get_param() call was left in the wrapper ahead of it. Patch 2 eliminates a duplicate override notice that appears when drivers call debug_set_level() right after debug_register(), which is the common pattern. With the s390dbf= parameter active and many devices (e.g. many DASDs), this produced a lot of redundant log lines during boot. Patch 3 fixes a pre-existing race between debug area resize and event logging. Setting pages to zero via the debugfs interface races with concurrent event writers: the unlocked id->areas check passes, but by the time the lock is acquired debug_areas_swap() may have published a NULL pointer, which get_active_entry() then dereferences. The race was confirmed to hang the system in testing by running concurrent debug area resize (pages 0->4 in a tight loop) against parallel DASD I/O. Changes in v3: - Patch 3: put back !id->areas check under lock in debug_flush() and remove existing !id->areas check before the lock (Peter Oberparleiter) Changes in v2: - Patch 1: Trimmed commit message; !id check removed from _debug_set_level() (Peter Oberparleiter) - Patch 3: Trimmed commit message; !id->areas check removed from debug_flush() (Peter Oberparleiter) Mikhail Zaslonko (3): s390/debug: Fix NULL pointer dereference in debug_set_level() s390/debug: Do not repeat parameter override notice on debug_set_level() s390/debug: Fix race between debug area resize and event logging arch/s390/kernel/debug.c | 54 ++++++++++++++++++++++++++-------------- 1 file changed, 36 insertions(+), 18 deletions(-) -- 2.55.0