From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4C9D8266580; Tue, 8 Apr 2025 12:23:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744115001; cv=none; b=NPAGWKucJJJvtWAdJ4yf2c0Cu6Eq7W+r6dcruMmaKORoeH+ctvbTa7LpXKB55MqnkG3XOSyGBCTGE1aEX1YTgKF7ZANMKF/t/+KwZ2MxoscGT/+qN3rRSgOznkR+K1EIpGhUvm+om8LdreEtFvVzFIJjhP1t2zD+W4Hqb2gU+3c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744115001; c=relaxed/simple; bh=hzLD98MSQcuvICfhry29TSeCcYwF/b2id1INU2Hsoec=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=MomU3P9rMquRk9ZLXkoxN6/cPn/CXydtecTlk1G8xrbucmONlcXoGDMAqD+R39Tglrs44h3ouYjdZgmfmQw0jtei2jdgdF4n4tVqTySRSTM5LE1tWKe6gSKkBV+vxvKifrnTtOMFlUNAxaXajFA5rFnRp5KseCirozwxpeo7T0o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=DjgZivJn; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="DjgZivJn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CFE37C4CEE5; Tue, 8 Apr 2025 12:23:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1744115001; bh=hzLD98MSQcuvICfhry29TSeCcYwF/b2id1INU2Hsoec=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=DjgZivJntbbBjPleufCUlKL3KQ0VgJ2qCp2UQpMLvTNBe1KkKqolM8/uNkaerHWNi wfgPhdyVeryiQeYZR9HWWUH2+bxDrfYGQ/11yKY4faJ0coPWMK4ZI3TTD1fBjySC9Q ykVmzj8CcIwehTIwZwJsT1Mzg7BdztEEXqbGbplw= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Peter Zijlstra (Intel)" , Ingo Molnar , Sasha Levin Subject: [PATCH 6.13 313/499] perf/core: Fix perf_pmu_register() vs. perf_init_event() Date: Tue, 8 Apr 2025 12:48:45 +0200 Message-ID: <20250408104859.026251088@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250408104851.256868745@linuxfoundation.org> References: <20250408104851.256868745@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.13-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra [ Upstream commit 003659fec9f6d8c04738cb74b5384398ae8a7e88 ] There is a fairly obvious race between perf_init_event() doing idr_find() and perf_pmu_register() doing idr_alloc() with an incompletely initialized PMU pointer. Avoid by doing idr_alloc() on a NULL pointer to register the id, and swizzling the real struct pmu pointer at the end using idr_replace(). Also making sure to not set struct pmu members after publishing the struct pmu, duh. [ introduce idr_cmpxchg() in order to better handle the idr_replace() error case -- if it were to return an unexpected pointer, it will already have replaced the value and there is no going back. ] Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20241104135517.858805880@infradead.org Signed-off-by: Sasha Levin --- kernel/events/core.c | 28 ++++++++++++++++++++++++++-- 1 file changed, 26 insertions(+), 2 deletions(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 43a44a6e243b1..1cecf092db808 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -11787,6 +11787,21 @@ static int pmu_dev_alloc(struct pmu *pmu) static struct lock_class_key cpuctx_mutex; static struct lock_class_key cpuctx_lock; +static bool idr_cmpxchg(struct idr *idr, unsigned long id, void *old, void *new) +{ + void *tmp, *val = idr_find(idr, id); + + if (val != old) + return false; + + tmp = idr_replace(idr, new, id); + if (IS_ERR(tmp)) + return false; + + WARN_ON_ONCE(tmp != val); + return true; +} + int perf_pmu_register(struct pmu *pmu, const char *name, int type) { int cpu, ret, max = PERF_TYPE_MAX; @@ -11813,7 +11828,7 @@ int perf_pmu_register(struct pmu *pmu, const char *name, int type) if (type >= 0) max = type; - ret = idr_alloc(&pmu_idr, pmu, max, 0, GFP_KERNEL); + ret = idr_alloc(&pmu_idr, NULL, max, 0, GFP_KERNEL); if (ret < 0) goto free_pdc; @@ -11821,6 +11836,7 @@ int perf_pmu_register(struct pmu *pmu, const char *name, int type) type = ret; pmu->type = type; + atomic_set(&pmu->exclusive_cnt, 0); if (pmu_bus_running && !pmu->dev) { ret = pmu_dev_alloc(pmu); @@ -11869,14 +11885,22 @@ int perf_pmu_register(struct pmu *pmu, const char *name, int type) if (!pmu->event_idx) pmu->event_idx = perf_event_idx_default; + /* + * Now that the PMU is complete, make it visible to perf_try_init_event(). + */ + if (!idr_cmpxchg(&pmu_idr, pmu->type, NULL, pmu)) + goto free_context; list_add_rcu(&pmu->entry, &pmus); - atomic_set(&pmu->exclusive_cnt, 0); + ret = 0; unlock: mutex_unlock(&pmus_lock); return ret; +free_context: + free_percpu(pmu->cpu_pmu_context); + free_dev: if (pmu->dev && pmu->dev != PMU_NULL_DEV) { device_del(pmu->dev); -- 2.39.5