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 9A5BA269885; Tue, 8 Apr 2025 11:57:53 +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=1744113473; cv=none; b=YrSeSbQ4x6C1jB3uRHmzSZveGzhVlW1j5qXvKqBb31UMggpNLSbbSu5/fhBV0R6gp4GUqMx+I7VsZRwyTileLluN2W/r1J4RpVoTHG0MPcjDl1VQ5dc7gIvPBD5J1arU+knxiB0n+HbykqabirdcsxYnoAhEccJez+IX7wHb4w0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744113473; c=relaxed/simple; bh=fnKfMzZWQk4jRxKHk/6e5RgwhSOmLIvh1nNG1schVsg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SZ2lX1ojRxj3PAJ1fs2GYjdfz+SiwiCtJkg4zbJlXW+3fLHlfk3AJalnIj78iStbxMfw6Wq63U4Uq13UusK18tKtqD7eVhf51vp2sdc3Y4u8qsv4YT2go4uLuXz/wu0ATfn8zyQdd/wOYUx445IZ+f+/+pKee2IQi3wL0VwwYlE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=hXciJjZq; 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="hXciJjZq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BB647C4CEEA; Tue, 8 Apr 2025 11:57:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1744113473; bh=fnKfMzZWQk4jRxKHk/6e5RgwhSOmLIvh1nNG1schVsg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hXciJjZq4njt5Oqe06FV0CYaQbUyuYD1Cox3t4lLvtV19UBGgaSzi81ClV05IbM6L 7Qc5jCL1FtKGpeG1ri8DKobjwmK+mZ2fzLVpU7mFI4Y8hkBY9GACxV1eJl8z3ea7HU YPkJN/OEQhbFRX8Sc7LTURamP49vddYNIxUGZt7s= 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 6.6 172/268] perf/core: Fix perf_pmu_register() vs. perf_init_event() Date: Tue, 8 Apr 2025 12:49:43 +0200 Message-ID: <20250408104833.182601192@linuxfoundation.org> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250408104828.499967190@linuxfoundation.org> References: <20250408104828.499967190@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 6.6-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 4dd8936b5aa09..a524329149a71 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -11556,6 +11556,21 @@ 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; @@ -11577,7 +11592,7 @@ 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; @@ -11585,6 +11600,7 @@ 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); @@ -11633,14 +11649,22 @@ 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