From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E41C8F531C3 for ; Mon, 13 Apr 2026 18:58:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=VjFtx9TVBimLo04LBzVCxDrDPfkzHb5EM3/axl9LJyE=; b=VBfAGWXtiRCI9ZoqhkPkqh7e8M ZFtM/z6HzuANWZyOwrZxGtmM7cdUypAF72TRt7QIIX5So47BUZVeSdc5z7Y6a14/vLwBjzKUlCKr/ omgXC+QqnKZGo50LoyM/qhBWBrvRScDFoowfPLofkNVAjZT5JKoKExB933nIL1ccNTtVndBkwQxZH cHnv6bLkzV66hY2rKjZ0aGVVcDowmPYLJJYbjPPeMg1FvHgVIuHe6v7rcvraj8Rz8WlytfV5o6W5U o3tyeyiMsSwlMvKfWd6u+1GaTeCeQQFt0sVK6KoXLPrUFss4THf+ZsoerJVaij/gllAvgPaLelhVS Bs1OPLXg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wCMUO-0000000GFCq-1JVC; Mon, 13 Apr 2026 18:58:28 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wCMUN-0000000GFCT-0FG3 for linux-arm-kernel@lists.infradead.org; Mon, 13 Apr 2026 18:58:27 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 7B4856183C; Mon, 13 Apr 2026 18:58:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 064C5C2BCAF; Mon, 13 Apr 2026 18:58:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776106706; bh=oWNqShly/dKLm6QH9Zz4OONYsqdxohN3rWDpuNVVnD0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hK8Vv8mFgWDEIp9XPGid+4bIdY5R6vAfgVzhC5yYWCbpVPhECmnS2bvbCv5BxyxdM usE7681SvMHyn2wOlNh3VFVCVLOrfc/Xe4wGG+8t4pQZ4g0yMwHEhMXe2YsTQHHrTM z7MP/uKNR0Geo2pb9YqogClOhStG9iRjwNXtC35CdomBUpIKpLOFfmpYKmLLefDPvr QQH3P+VBHZNeZFJzGesa6y28nsQMuRDln61sGFocqRxejcgoUBH4plyc4bjsBAb3o0 qOtWLEc091pg2B6yGz7Hdes+cNQJCLpFlpXyrsFZQu4jh/cdU1D6HsI5z42lA5CtTX CvQVceOLPneqQ== From: Puranjay Mohan To: bpf@vger.kernel.org Cc: Puranjay Mohan , Puranjay Mohan , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , Will Deacon , Mark Rutland , Catalin Marinas , Leo Yan , Rob Herring , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , James Clark , Ian Rogers , Adrian Hunter , Shuah Khan , Breno Leitao , Ravi Bangoria , Stephane Eranian , Kumar Kartikeya Dwivedi , Usama Arif , linux-arm-kernel@lists.infradead.org, linux-perf-users@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: [PATCH v3 1/4] perf/core: Fix NULL pmu_ctx passed to PMU sched_task callback Date: Mon, 13 Apr 2026 11:57:20 -0700 Message-ID: <20260413185740.3286146-2-puranjay@kernel.org> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260413185740.3286146-1-puranjay@kernel.org> References: <20260413185740.3286146-1-puranjay@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org __perf_pmu_sched_task() passes cpc->task_epc to pmu->sched_task(), which is NULL when no per-task events exist for this PMU. With CPU-wide branch-stack events, PMU callbacks that dereference pmu_ctx crash. On ARM64 this is easily triggered with: perf record -b -e cycles -a -- ls which crashes on the first context switch: Unable to handle kernel NULL pointer dereference at virtual address 00[.] PC is at armv8pmu_sched_task+0x14/0x50 Call trace: armv8pmu_sched_task+0x14/0x50 (P) perf_pmu_sched_task+0xac/0x108 __perf_event_task_sched_out+0x6c/0xe0 Fall back to &cpc->epc when cpc->task_epc is NULL so the callback always receives a valid pmu_ctx. Fixes: bd2756811766 ("perf: Rewrite core context handling") Signed-off-by: Puranjay Mohan --- kernel/events/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 1f5699b339ec..2a8fb78e1347 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3906,7 +3906,8 @@ static void __perf_pmu_sched_task(struct perf_cpu_pmu_context *cpc, perf_ctx_lock(cpuctx, cpuctx->task_ctx); perf_pmu_disable(pmu); - pmu->sched_task(cpc->task_epc, task, sched_in); + pmu->sched_task(cpc->task_epc ? cpc->task_epc : &cpc->epc, + task, sched_in); perf_pmu_enable(pmu); perf_ctx_unlock(cpuctx, cpuctx->task_ctx); -- 2.52.0