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Tue, 22 Sep 2026 10:35:02 +0000 (GMT) Received: from osiris (unknown [9.87.153.113]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTPS; Tue, 22 Sep 2026 10:35:02 +0000 (GMT) Date: Tue, 22 Sep 2026 12:35:01 +0200 From: Heiko Carstens To: Mikhail Zaslonko Cc: linux-s390@vger.kernel.org, Alexander Gordeev , Vasily Gorbik , Peter Oberparleiter Subject: Re: [PATCH v2] s390/debug: Fix NULL pointer dereference in debug_info_copy() Message-ID: <20260922103501.10121Aba-hca@linux.ibm.com> References: <20260916160626.1988684-1-zaslonko@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260916160626.1988684-1-zaslonko@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: 36mt5-hQ3ZX5UVJUqqC-H3FpPkuZ520v X-Authority-Analysis: v=2.4 cv=I43w19gg c=1 sm=1 tr=0 ts=6ab259db cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=kj9zAlcOel0A:10 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=gheRGZjsO9QmUI7mxtoA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTIyMDE1MiBTYWx0ZWRfXwwLkbvVeSO2E /a9819T27OXWbfgqzu1EHvpM1pcksT20RdQ0x4alnBQxWjnosxi0laUAPggvCeUcsnssfxik5FE CiAqiKmZEKi/pXfz79NYSEEp4QDpc1qFCN8ea77pPukHrrYzJUbgFWfxYi/Gdf8JjfmM5osHG2j o94mZYLV6M9XAeS9GmkDxXNnMRBgV2kyYDMvmVQJns1uXSuJcfYto5LL/JkjcYJk6Yg1ud+S/pT LHITttDt8q9tLjb+O2O50LNeXMdjGXUcqF6TatT/oqWJF+KK1R9dmlqJYHfmwcbuAlfo1ztwXyM 0Q50RP/dPewFRw5qZbPj1eKF0Z5FrLgvuqwKznBU7WJ/Q9ns00nEeSpVey2hAr7DmZWrwJdAd9v BgyDSenni44memOLaqf+e8/tZo/hNEfEJE1nPGM3KAlkZLKg/EJF9Ev+H0aNSlQLzocr2rAkTvq l00sf80zfbCNS1/fJXw== X-Proofpoint-Spam-Info: AW1haW4tMjYwOTIyMDE1MiBTYWx0ZWRfXxWINBcq+ydin dhl8So9gz/X08KsaXcg0HVjGzBlTmH7zA3cR+X9Yd65duZ6CVOFv9aEM5iFHXBMxNpBXojJ/M0G /2AOGXzFowHcOCy+gWPMwpfG++pIt6g= X-Proofpoint-GUID: 36mt5-hQ3ZX5UVJUqqC-H3FpPkuZ520v 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=2026-09-21_07,2026-09-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 clxscore=1015 adultscore=0 suspectscore=0 impostorscore=0 lowpriorityscore=0 bulkscore=0 phishscore=0 priorityscore=1501 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609220152 On Wed, Sep 16, 2026 at 06:06:26PM +0200, Mikhail Zaslonko wrote: > When debug_register_static() fails, it clears areas, active_pages and > active_entries but leaves the area bounds unchanged. Copying such an > area, either by opening its view file or via debug_dump(), makes > debug_info_copy() dereference the NULL pointers. > > Skip the copy loop when the source has no areas. > > Closes: https://lore.kernel.org/r/20260903132123.12F271F00A3F@smtp.kernel.org > Fixes: d72541f94512 ("s390/debug: add early tracing support") > Signed-off-by: Mikhail Zaslonko > --- > v2: > - Different approach: check the areas pointer in debug_info_copy() > instead of zeroing nr_areas/pages_per_area in debug_register_static(). > Zeroing nr_areas made debug_info_alloc() return ZERO_SIZE_PTR for > active_pages/active_entries, which debug_to_act_entry() dereferences > before debug_prev_entry() checks id->areas. > Checking the pointer also matches what all other readers in this file > already do. > - v1: https://lore.kernel.org/all/20260910104525.3788362-1-zaslonko@linux.ibm.com/ > > arch/s390/kernel/debug.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) Applied, thanks!