From patchwork Wed Nov 18 14:50:09 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nishanth Menon X-Patchwork-Id: 11915293 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=-18.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, 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 autolearn=unavailable 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 DF80BC63777 for ; Wed, 18 Nov 2020 14:51:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8531E246EB for ; Wed, 18 Nov 2020 14:51:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ti.com header.i=@ti.com header.b="ufkgw32S" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727186AbgKROui (ORCPT ); Wed, 18 Nov 2020 09:50:38 -0500 Received: from fllv0015.ext.ti.com ([198.47.19.141]:39370 "EHLO fllv0015.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727161AbgKROui (ORCPT ); Wed, 18 Nov 2020 09:50:38 -0500 Received: from lelv0265.itg.ti.com ([10.180.67.224]) by fllv0015.ext.ti.com (8.15.2/8.15.2) with ESMTP id 0AIEoJSD112404; Wed, 18 Nov 2020 08:50:19 -0600 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1605711019; bh=/WfMKfpfaqPhwhCkATAAiFh4DbZHut//34CHnfa7pU8=; h=From:To:CC:Subject:Date; b=ufkgw32S/4yo2MS7xBQe7neGZibn0mxh8sp5Siikv+ns+ta8Dp6HDAR7Nncpd2xd9 1+3HXgQqWmGtZCXHlbz45JbHA4DsufHe9uChUxtMh59F9sQz9HgU6PWoXpG9rKB93I lHytBggqescJqQWtSv7oGuGB0rD+iDI+woCP8fEQ= Received: from DLEE104.ent.ti.com (dlee104.ent.ti.com [157.170.170.34]) by lelv0265.itg.ti.com (8.15.2/8.15.2) with ESMTPS id 0AIEoJch055732 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Wed, 18 Nov 2020 08:50:19 -0600 Received: from DLEE101.ent.ti.com (157.170.170.31) by DLEE104.ent.ti.com (157.170.170.34) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1979.3; Wed, 18 Nov 2020 08:50:19 -0600 Received: from fllv0040.itg.ti.com (10.64.41.20) by DLEE101.ent.ti.com (157.170.170.31) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1979.3 via Frontend Transport; Wed, 18 Nov 2020 08:50:19 -0600 Received: from localhost (ileax41-snat.itg.ti.com [10.172.224.153]) by fllv0040.itg.ti.com (8.15.2/8.15.2) with ESMTP id 0AIEoJ9A113879; Wed, 18 Nov 2020 08:50:19 -0600 From: Nishanth Menon To: Mark Brown , Liam Girdwood CC: , , , , , Naresh Kamboju , Arnd Bergmann , Nishanth Menon Subject: [PATCH] regulator: ti-abb: Fix array out of bound read access on the first transition Date: Wed, 18 Nov 2020 08:50:09 -0600 Message-ID: <20201118145009.10492-1-nm@ti.com> X-Mailer: git-send-email 2.29.2 MIME-Version: 1.0 X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Precedence: bulk List-ID: X-Mailing-List: linux-omap@vger.kernel.org At the start of driver initialization, we do not know what bias setting the bootloader has configured the system for and we only know for certain the very first time we do a transition. However, since the initial value of the comparison index is -EINVAL, this negative value results in an array out of bound access on the very first transition. Since we don't know what the setting is, we just set the bias configuration as there is nothing to compare against. This prevents the array out of bound access. NOTE: Even though we could use a more relaxed check of "< 0" the only valid values(ignoring cosmic ray induced bitflips) are -EINVAL, 0+. Fixes: 40b1936efebd ("regulator: Introduce TI Adaptive Body Bias(ABB) on-chip LDO driver") Link: https://lore.kernel.org/linux-mm/CA+G9fYuk4imvhyCN7D7T6PMDH6oNp6HDCRiTUKMQ6QXXjBa4ag@mail.gmail.com/ Reported-by: Naresh Kamboju Reviewed-by: Arnd Bergmann Signed-off-by: Nishanth Menon --- Mark, I will leave it to your descretion if this needs to be tagged for stable or to drop the Fixes tag - Side effect, if this occurs, will be an unstable system very hard to track down - but typically occurring during system boot - Impacts systems: DM3/OMAP3,4,5,DRA7/AM5x. I would categorize this as "This could be a problem..." problem.. the bug is an out of bound read, and has been around since v3.11 and is not a catastrophic data corruption kind of issue. Though theoretically, there is a possibility that the compare may pass and result in missing bias configuration(and resulting system will be unstable), I have'nt heard of actual report (but, it will be surprising if any actual instability was actually tracked down to this bug). Any ways, I had to go to git full history to pick the exact commit - I have left it in the patch. Arnd, I have left your reviewed-by from the thread, I can fixup any further commit message comments if you may have. drivers/regulator/ti-abb-regulator.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/regulator/ti-abb-regulator.c b/drivers/regulator/ti-abb-regulator.c index 3e60bff76194..9f0a4d50cead 100644 --- a/drivers/regulator/ti-abb-regulator.c +++ b/drivers/regulator/ti-abb-regulator.c @@ -342,8 +342,17 @@ static int ti_abb_set_voltage_sel(struct regulator_dev *rdev, unsigned sel) return ret; } - /* If data is exactly the same, then just update index, no change */ info = &abb->info[sel]; + /* + * When Linux kernel is starting up, we are'nt sure of the + * Bias configuration that bootloader has configured. + * So, we get to know the actual setting the first time + * we are asked to transition. + */ + if (abb->current_info_idx == -EINVAL) + goto just_set_abb; + + /* If data is exactly the same, then just update index, no change */ oinfo = &abb->info[abb->current_info_idx]; if (!memcmp(info, oinfo, sizeof(*info))) { dev_dbg(dev, "%s: Same data new idx=%d, old idx=%d\n", __func__, @@ -351,6 +360,7 @@ static int ti_abb_set_voltage_sel(struct regulator_dev *rdev, unsigned sel) goto out; } +just_set_abb: ret = ti_abb_set_opp(rdev, abb, info); out: