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 11F0F12CD9B; Tue, 30 Apr 2024 11:15:05 +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=1714475705; cv=none; b=LI7blnWliRm3SPlD+TxkVabgx4GsnNHs4x1ARBTp2KLKJECjlcNwTr12zdPuH4Bpfuv0Eyblz6Ot51HS1Fs2VcvOzsaRykQnhWAZJWH1CsLnYTHU2w6UYBysIeISoIo15DgYggxpGr5IqhrZQ22Ue9QXl6gqAOQzV3G138MzBjI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714475705; c=relaxed/simple; bh=uKR3p7HHsAJQ44tDIyvKSlWrgUFWBitQXWGG0qoIDIQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Zjq2EhDaT5mj35aYjl94+rKdhJYRhEOLzuS48S44AVRwcpx6z7Mkf92TgJtx2bESu9DRkkAWpL1vEK7jaDq6qIFbjxoctHsU/Hi/E3DQqZDa+n1QKLkIj9c7UkouQM63Qe8t81e3/egN7u/qnDPkvr3eFvueYGCHKliIpS3s1LI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=rlpy6Gje; 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="rlpy6Gje" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 78F5AC2BBFC; Tue, 30 Apr 2024 11:15:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1714475704; bh=uKR3p7HHsAJQ44tDIyvKSlWrgUFWBitQXWGG0qoIDIQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rlpy6Gje8ubpSYLhNEgnBIbceBfmLkMANWxXqftWJqdQhPIaSVk077Al0qy1ZDkmE pgoDfa0HlHsfleSJScZIDKISNrVvz8qCKHSO44WFwabvCMNY68KViXfF2wfFsbt8a5 p4p/r6Ep0hLjG/FNfjTczduM67jpbbDSlYlETKhs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Sergei Trofimovich , Igor Raits , Breno Leitao , kernel test robot , Yujie Liu , Xuewen Yan , "Peter Zijlstra (Intel)" , Sasha Levin , Chen Yu Subject: [PATCH 6.6 178/186] sched/eevdf: Prevent vlag from going out of bounds in reweight_eevdf() Date: Tue, 30 Apr 2024 12:40:30 +0200 Message-ID: <20240430103103.198157606@linuxfoundation.org> X-Mailer: git-send-email 2.44.0 In-Reply-To: <20240430103058.010791820@linuxfoundation.org> References: <20240430103058.010791820@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev 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: Xuewen Yan [ Upstream commit 1560d1f6eb6b398bddd80c16676776c0325fe5fe ] It was possible to have pick_eevdf() return NULL, which then causes a NULL-deref. This turned out to be due to entity_eligible() returning falsely negative because of a s64 multiplcation overflow. Specifically, reweight_eevdf() computes the vlag without considering the limit placed upon vlag as update_entity_lag() does, and then the scaling multiplication (remember that weight is 20bit fixed point) can overflow. This then leads to the new vruntime being weird which then causes the above entity_eligible() to go side-ways and claim nothing is eligible. Thus limit the range of vlag accordingly. All this was quite rare, but fatal when it does happen. Closes: https://lore.kernel.org/all/ZhuYyrh3mweP_Kd8@nz.home/ Closes: https://lore.kernel.org/all/CA+9S74ih+45M_2TPUY_mPPVDhNvyYfy1J1ftSix+KjiTVxg8nw@mail.gmail.com/ Closes: https://lore.kernel.org/lkml/202401301012.2ed95df0-oliver.sang@intel.com/ Fixes: eab03c23c2a1 ("sched/eevdf: Fix vruntime adjustment on reweight") Reported-by: Sergei Trofimovich Reported-by: Igor Raits Reported-by: Breno Leitao Reported-by: kernel test robot Reported-by: Yujie Liu Signed-off-by: Xuewen Yan Reviewed-and-tested-by: Chen Yu Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20240422082238.5784-1-xuewen.yan@unisoc.com Signed-off-by: Sasha Levin --- kernel/sched/fair.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a5466eb6a1f15..397ef27c9bdb1 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -707,15 +707,21 @@ u64 avg_vruntime(struct cfs_rq *cfs_rq) * * XXX could add max_slice to the augmented data to track this. */ -static void update_entity_lag(struct cfs_rq *cfs_rq, struct sched_entity *se) +static s64 entity_lag(u64 avruntime, struct sched_entity *se) { - s64 lag, limit; + s64 vlag, limit; + + vlag = avruntime - se->vruntime; + limit = calc_delta_fair(max_t(u64, 2*se->slice, TICK_NSEC), se); + + return clamp(vlag, -limit, limit); +} +static void update_entity_lag(struct cfs_rq *cfs_rq, struct sched_entity *se) +{ SCHED_WARN_ON(!se->on_rq); - lag = avg_vruntime(cfs_rq) - se->vruntime; - limit = calc_delta_fair(max_t(u64, 2*se->slice, TICK_NSEC), se); - se->vlag = clamp(lag, -limit, limit); + se->vlag = entity_lag(avg_vruntime(cfs_rq), se); } /* @@ -3710,7 +3716,7 @@ static void reweight_eevdf(struct sched_entity *se, u64 avruntime, * = V - vl' */ if (avruntime != se->vruntime) { - vlag = (s64)(avruntime - se->vruntime); + vlag = entity_lag(avruntime, se); vlag = div_s64(vlag * old_weight, weight); se->vruntime = avruntime - vlag; } -- 2.43.0