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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_GIT 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 7F8F5C47082 for ; Mon, 7 Jun 2021 14:15:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5DC756108E for ; Mon, 7 Jun 2021 14:15:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230282AbhFGORU (ORCPT ); Mon, 7 Jun 2021 10:17:20 -0400 Received: from mailgw01.mediatek.com ([210.61.82.183]:60228 "EHLO mailgw01.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S230231AbhFGORT (ORCPT ); Mon, 7 Jun 2021 10:17:19 -0400 X-UUID: 113a9878a26848eab2c72452ee82e5d0-20210607 X-UUID: 113a9878a26848eab2c72452ee82e5d0-20210607 Received: from mtkmbs10n2.mediatek.inc [(172.21.101.183)] by mailgw01.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384 256/256) with ESMTP id 729966752; Mon, 07 Jun 2021 22:15:24 +0800 Received: from mtkcas11.mediatek.inc (172.21.101.40) by mtkmbs08n1.mediatek.inc (172.21.101.55) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Mon, 7 Jun 2021 22:15:22 +0800 Received: from mtksdccf07.mediatek.inc (172.21.84.99) by mtkcas11.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Mon, 7 Jun 2021 22:15:22 +0800 From: Mark-PK Tsai To: CC: , , , , , , , , Subject: Re: [PATCH] arm64: ftrace: don't dereference a probably invalid address Date: Mon, 7 Jun 2021 22:15:22 +0800 Message-ID: <20210607141522.3281-1-mark-pk.tsai@mediatek.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20210607095518.12694437@oasis.local.home> References: <20210607095518.12694437@oasis.local.home> MIME-Version: 1.0 Content-Type: text/plain X-MTK: N Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Mon, 7 Jun 2021 11:23:30 +0800 > Mark-PK Tsai wrote: > > > Address in __mcount_loc may be invalid if somthing goes wrong. > > On our arm64 platform, the bug in recordmcount make kernel > > crash in ftrace_init(). > > How did it crash? The link below doesn't show any crash. Below is the crash log: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 0 at kernel/trace/ftrace.c:2008 ftrace_bug+0x9c/0x38c Modules linked in: CPU: 0 PID: 0 Comm: swapper Tainted: G W 5.4.61-350609-gf78fedda5a5e #1 Hardware name: MediaTek MT5896 (DT) pstate: 60400089 (nZCv daIf +PAN -UAO) pc : ftrace_bug+0x9c/0x38c lr : ftrace_process_locs+0x314/0x3b8 sp : ffffffc011743ef0 x29: ffffffc011743f00 x28: 0000000000000001 x27: ffffff818e401b80 x26: 0000000000000000 x25: ffffff818e480008 x24: ffffffc011749000 x23: 0000000000000008 x22: 0000000000000000 x21: ffffffc010084ac0 x20: 0000000000000024 x19: ffffff818e480000 x18: ffffffc011759c20 x17: ffffffc01133dcf8 x16: 0000000000000068 x15: ffffffc01133dcf8 x14: 0000000000000000 x13: 0000000000000000 x12: ffffffc010084ae4 x11: ffffffc011749000 x10: ffffffc011749000 x9 : 0000000000000001 x8 : ffffffc011749000 x7 : 0000000000000000 x6 : 000000000000003f x5 : 000000000008e93d x4 : 0000000000000000 x3 : 0000000000000101 x2 : ffffffc010084ac0 x1 : ffffff818e480000 x0 : ffffffc01127621c Call trace: ftrace_bug+0x9c/0x38c ftrace_process_locs+0x314/0x3b8 ftrace_init+0x8c/0xbc start_kernel+0x180/0x40c ---[ end trace 59db467eb74a6604 ]--- ftrace failed to modify [<0000000000000024>] 0x24 actual: "Unable to handle kernel read from unreadable memory at virtual address 0000000000000024 "Mem abort info: And the crash is becuase kernel trying to read *rec->ip in print_ip_ins() if ftrace_bug() get error code -EINVAL. > > > > > https://lore.kernel.org/lkml/20210607023839.26387-1-mark-pk.tsai@mediatek.com/ > > > > Return -EFAULT if we are dealing with out-of-range condition > > to prevent dereference the invalid address in ftrace_bug(), > > then the kernel can disable ftrace safely for problematic > > __mcount_loc. > > !mod is not an out-of-range condition. It just happened that the other > bug caused this strange side-effect. A !mod does not mean a fault > happened. Just because it may have been caused by a fault in your use > case does not mean that it's a fault in all use cases. That's like > saying that your dog is a poodle, so all dogs are poodles. > > A return of -EINVAL should not cause a crash. If it does, then that > needs to be fixed. I understand. Keep -EINVAL here make more sense. So maybe we should handle this case in ftrace_bug() by checking the rec->ip? > > -- Steve > > > > > > Signed-off-by: Mark-PK Tsai > > --- > > arch/arm64/kernel/ftrace.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c > > index b5d3ddaf69d9..98bec8445a58 100644 > > --- a/arch/arm64/kernel/ftrace.c > > +++ b/arch/arm64/kernel/ftrace.c > > @@ -201,7 +201,7 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, > > preempt_enable(); > > > > if (WARN_ON(!mod)) > > - return -EINVAL; > > + return -EFAULT; > > } > > > > /*