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Wed, 13 May 2026 09:20:40 +0000 (GMT) Received: from [9.52.200.195] (unknown [9.52.200.195]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 13 May 2026 09:20:39 +0000 (GMT) Message-ID: Date: Wed, 13 May 2026 11:20:39 +0200 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v14 11/19] unwind_user/sframe: Show file name in debug output From: Jens Remus To: Steven Rostedt , Josh Poimboeuf Cc: bpf@vger.kernel.org, sashiko@lists.linux.dev, Indu Bhagat , Heiko Carstens References: <20260505121718.3572346-12-jremus@linux.ibm.com> <20260505184638.5648DC2BCB4@smtp.kernel.org> Content-Language: en-US Organization: IBM Deutschland Research & Development GmbH In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=Us1T8ewB c=1 sm=1 tr=0 ts=6a04426b cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=VwQbUJbxAAAA:8 a=0MvmVg10__VCTnNSAJcA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: eajoxDX7UYy6UqVBMykyXRGTaSxANpgM X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTEzMDA5NCBTYWx0ZWRfX96Wp664p85tg AljJKvZrKZkGrUEuT0bc6tj/yYhN9NJdnr7IsCsHCUFRlNMDchdLAIzyMpXSJjX75r87Pj9zvkl At3bxNECBln9CGoWxOdQJqMolqqgaIVSizUuBozAiELJCAerT/eSuqYoBmIbvyiI/FoHMJqPO+Y xOGuG7L61iVSKZeAQc5JGVYZX6s5uI3KuH13eFO/OigGVqxaSgDa9bePcqcbKFyzcWjQNCSZjlH m3JquUe5saniMdAlXVIsLlP3TDCdB+Y83uXyQfBYa0Bw+mzQncfObiRSc1zsXv1i+4VZjL84F+A /IHwTFgWXmxLE3ylNXJ7vDLEAnae/fWmya91+u0U/qbU9mdp3rBjxeHgoGBZievnFOxieAgIXMi +s5546XCPE4zsO0FY2cuhIN6uV/6sWFqLC2K3dOuwUWpZHBFExEjNLmJQYuYhAcXwXF/ovhW0hN iXHXb0JaPtCkoyfrghg== X-Proofpoint-ORIG-GUID: dEsWO2sHdweVIFkg_oyCXmxZh8d5U2Gi X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-11_05,2026-05-08_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 priorityscore=1501 impostorscore=0 lowpriorityscore=0 bulkscore=0 suspectscore=0 spamscore=0 malwarescore=0 clxscore=1015 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605050000 definitions=main-2605130094 On 5/12/2026 4:52 PM, Jens Remus wrote: > On 5/5/2026 8:46 PM, sashiko-bot@kernel.org wrote: > >> [ ... ] >>> @@ -496,7 +501,7 @@ static int __sframe_remove_section(struct mm_struct *mm, >>> struct sframe_section *sec) >>> { >>> if (!mtree_erase(&mm->sframe_mt, sec->text_start)) { >>> - dbg("mtree_erase failed: text=%lx\n", sec->text_start); >>> + dbg_sec("mtree_erase failed: text=%lx\n", sec->text_start); >> >> Does accessing sec->filename in dbg_sec() risk a use-after-free here? If >> mtree_erase() fails, it indicates the section might have been concurrently >> removed. The SRCU grace period could expire, causing sec to be freed before >> dbg_sec() is called. > > IIUC this is a valid concern. Should this change be simply be reverted > or should __sframe_remove_section() create a temporary copy of the > filename and use dbg() for this rather unlikely case? On my way home it occurred to me that adding guard(srcu)(&sframe_srcu); to sframe_remove_section() (see my feedback on "[PATCH v14 03/19] unwind_user/sframe: Store .sframe section data in per-mm maple tree") should also resolve this use-after-free without any need for changes. Regards, Jens -- Jens Remus Linux on Z Development (D3303) jremus@de.ibm.com / jremus@linux.ibm.com IBM Deutschland Research & Development GmbH; Vorsitzender des Aufsichtsrats: Wolfgang Wendt; Geschäftsführung: David Faller; Sitz der Gesellschaft: Ehningen; Registergericht: Amtsgericht Stuttgart, HRB 243294 IBM Data Privacy Statement: https://www.ibm.com/privacy/