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 X-Spam-Level: X-Spam-Status: No, score=-26.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8C388C433B4 for ; Thu, 29 Apr 2021 15:27:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E12A60D07 for ; Thu, 29 Apr 2021 15:27:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240762AbhD2P1u (ORCPT ); Thu, 29 Apr 2021 11:27:50 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53484 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232989AbhD2P1s (ORCPT ); Thu, 29 Apr 2021 11:27:48 -0400 Received: from mail-wm1-x349.google.com (mail-wm1-x349.google.com [IPv6:2a00:1450:4864:20::349]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8736FC06138B for ; Thu, 29 Apr 2021 08:27:01 -0700 (PDT) Received: by mail-wm1-x349.google.com with SMTP id z135-20020a1c7e8d0000b02901297f50f20dso1505636wmc.0 for ; Thu, 29 Apr 2021 08:27:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:message-id:mime-version:subject:from:to:cc; bh=p0igZyrs5kNhrAalP/Bef9OTT/K+mc9eClA68h2BbGw=; b=g25g7eSv3DiOYvQLj9XcGvg72/wdAPGils2qsqtLeERwPsWbBt3tqc/oF6MYvyOzaQ Xz0ZMDjLqYlv85SfYdNgre/MZhNCsVPa5oWu4lrnDZlQGayGlxwZrup2hjX5As6ztpE8 nrjSrVkBvPZPWN11HbodPTRC9P+49h7CFZRYMRxwU9DmEOt/jh7pOkQoPmBwDYtFONLT ZOSxrB9qFOGNLgKAEoxjNvICIV9ZS+0+rLlE5hrW9p7xEJQuLIECC88Xpv90x9uXF6U0 Go5KX2EBQ0crdh+IenObEIeXhBZJ+oGuPdD/aaZDTOJ8mTNzwgYToOu679+51mHMNOQm DPZw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=p0igZyrs5kNhrAalP/Bef9OTT/K+mc9eClA68h2BbGw=; b=g5JQ2LomUxH6T4HYYVu2oe0YplhVsvkci1Vg+d2O+mfFonJtPJFH35uoyHzjBhQrRC 3TTZbG0uRGH4gY2B4w6tx2MVDlO5SwDxjYBnYT++btSU+ZWsh5QE8y2Zgyt6fQvw25wT w7rrf2SPbtoom/mE3IWLhAk5CxO4JTVvOnzGU1Pwbdfx4PNqcrUjJ31O6q+CZ/uGpB6o vlmlWawmTo+pxurIBNaZSXKcqDLg+IrO7iauuaG4KV6Pd/Q4wN1OqYoCWAcUmtH/Rn26 7f4JbHmoPvhlth0QvvmN39PjYqZa3fl2sM4MdwaucG2XcNZWoJcAFDu06bHISdNzA5TF N3rg== X-Gm-Message-State: AOAM532nuMLDtl9nlD+N7bpurSAF07q0OUcfPsvEDnFlaP2QuemF0T79 /LUOAAMeXJALC88LeWej3IcsXE9kIaxp X-Google-Smtp-Source: ABdhPJxGZl3J/RFxt6+Vl9aoO7k2oljSMnxglkps8BJDR/bwdVgtrSYGMYUXKftoy6ms3yYhy9QsfLnJaA9+ X-Received: from r2d2-qp.c.googlers.com ([fda3:e722:ac3:10:28:9cb1:c0a8:1652]) (user=qperret job=sendgmr) by 2002:a05:600c:499a:: with SMTP id h26mr643514wmp.176.1619710020173; Thu, 29 Apr 2021 08:27:00 -0700 (PDT) Date: Thu, 29 Apr 2021 15:26:56 +0000 Message-Id: <20210429152656.4118460-1-qperret@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.31.1.498.g6c1eba8ee3d-goog Subject: [PATCH v2] sched: Fix out-of-bound access in uclamp From: Quentin Perret To: mingo@redhat.com, peterz@infradead.org, vincent.guittot@linaro.org, juri.lelli@redhat.com Cc: dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, qais.yousef@arm.com, kernel-team@android.com, linux-kernel@vger.kernel.org, patrick.bellasi@matbug.net Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Util-clamp places tasks in different buckets based on their clamp values for performance reasons. However, the size of buckets is currently computed using a rounding division, which can lead to an off-by-one error in some configurations. For instance, with 20 buckets, the bucket size will be 1024/20=51. A task with a clamp of 1024 will be mapped to bucket id 1024/51=20. Sadly, correct indexes are in range [0,19], hence leading to an out of bound memory access. Fix the math to compute the bucket size. Fixes: 69842cba9ace ("sched/uclamp: Add CPU's clamp buckets refcounting") Suggested-by: Qais Yousef Signed-off-by: Quentin Perret --- Changes in v2: - replaced the DIV_ROUND_UP(a,b) with a/b+1 (Dietmar) This was found thanks to the SCHED_WARN_ON() in uclamp_rq_dec_id() which indicated a broken state while running with 20 buckets on Android. Big thanks to Qais for the help with this one. --- kernel/sched/core.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 98191218d891..c5fb230dc604 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -920,8 +920,7 @@ static struct uclamp_se uclamp_default[UCLAMP_CNT]; */ DEFINE_STATIC_KEY_FALSE(sched_uclamp_used); -/* Integer rounded range for each bucket */ -#define UCLAMP_BUCKET_DELTA DIV_ROUND_CLOSEST(SCHED_CAPACITY_SCALE, UCLAMP_BUCKETS) +#define UCLAMP_BUCKET_DELTA (SCHED_CAPACITY_SCALE / UCLAMP_BUCKETS + 1) #define for_each_clamp_id(clamp_id) \ for ((clamp_id) = 0; (clamp_id) < UCLAMP_CNT; (clamp_id)++) -- 2.31.1.498.g6c1eba8ee3d-goog