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Mon, 7 Sep 2026 10:32:39 +0000 (GMT) From: Thomas Richter To: linux-s390@vger.kernel.org Cc: Thomas Richter , Peter Zijlstra Subject: [PATCH] perf/core: Allow list_del during perf_event_overflow() Date: Mon, 7 Sep 2026 12:32:19 +0200 Message-ID: <20260907103219.3006700-1-tmricht@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-ORIG-GUID: nZvamkAY_rzpPuAa_GwsGcSHijfQsaFB X-Proofpoint-Spam-Info: AW1haW4tMjYwOTA3MDExNSBTYWx0ZWRfX+Ho35EGMbPN5 oSWMGsbTd6rrvDO64nu6M3PZT6DkPcikSKIWtVcmgLOLUcGv/kVQD6Xa5aQz7G9i5r6V8+isGuh Yp9MNyyWVJDq8Ti6SYy6fwfTXdzKqRU= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTA3MDExNSBTYWx0ZWRfX2KZ36THyXC+m n9PHHdkGamteKvhORbuJ3JGkidqvoI5ZE8bcckD61laByLCkpCdBFTI0Ih44Yssh71Q+oYCgg9N o/HWs9cFzdyc4o+u80o+zMvJv27TaHsikqcxiWHUKI+lc/mxzD3YT1dgBUe47d9AtGrGunA0eAy O+VmsJ16y7d46/YK6jx7fcBmvnacPNNMe+SCdR/ODZUo9UGH0vaDEv2e7GQ1tFiEURMiU9pED9x N48S5or2aZjjBQfZF1G0YZ63DrNIROVaPLA1XgpuTH3IQvBa6tA7MBDqrOecbt94GdomXKYVZt6 lzLuZNsxY9O6/Yg5XqrvDX2BsUCMbj7IFOs+Uburk5MMhXkEccur7zSViApq5iNDKnlCQrkWbTm mHGg44y3vs1zI8Qn6JzxZE5SWT3boBgtxRN99O892qIjzT587YTV05BNlb9wWF26/XA0G9/3un9 EU2TTxem+dDciNzGm+g== X-Authority-Analysis: v=2.4 cv=JaKMa0KV c=1 sm=1 tr=0 ts=6a9e92cc cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=JfrnYn6hAAAA:8 a=VnNF1IyMAAAA:8 a=tpjk3lqxN-sNga2Lk8kA:9 a=1CNFftbPRP8L7MoqJWF3:22 X-Proofpoint-GUID: nZvamkAY_rzpPuAa_GwsGcSHijfQsaFB 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=2026-09-07_02,2026-09-07_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 spamscore=0 phishscore=0 impostorscore=0 lowpriorityscore=0 adultscore=0 bulkscore=0 priorityscore=1501 suspectscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2609070115 A PMU might use perf_sched_cb_inc() and perf_sched_cb_dec() interface to get the PMU call back function pmu::sched_task invoked at schedule in and schedule out. This is achieved by walking along the list anchored by sched_cb_list. The following scenario might lead to a list corruption. perf_pmu_sched_task() for_each_list_entry(..., &sched_cb_list) +--> __perf_pmu_sched_task() +--> event->pmu->sched_task()) +--> PMU_push_sample() +--> perf_event_overflow() +--> __perf_event_overflow() +--> pmu->stop() +--> perf_sched_cb_dec() remove entry from sched_cb_list while list node in use. This happens when ioctl(fd, PERF_EVENT_IOC_REFRESH, xxx) has been invoked and perf_event::event_limit hits zero. Prevent the list corruption and convert for_each_list_entry() to for_each_list_entry_safe(). Cc: Peter Zijlstra Signed-off-by: Thomas Richter --- kernel/events/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index a6c8e38a3110..cdd9518ac046 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3925,13 +3925,13 @@ static void perf_pmu_sched_task(struct task_struct *prev, bool sched_in) { struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context); - struct perf_cpu_pmu_context *cpc; + struct perf_cpu_pmu_context *cpc, *cpc2; /* cpuctx->task_ctx will be handled in perf_event_context_sched_in/out */ if (prev == next || cpuctx->task_ctx) return; - list_for_each_entry(cpc, this_cpu_ptr(&sched_cb_list), sched_cb_entry) + list_for_each_entry_safe(cpc, cpc2, this_cpu_ptr(&sched_cb_list), sched_cb_entry) __perf_pmu_sched_task(cpc, sched_in ? next : prev, sched_in); } -- 2.55.0