From patchwork Wed Jan 19 01:50:25 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: He Ying X-Patchwork-Id: 1581622 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=lists.ozlabs.org (client-ip=112.213.38.117; helo=lists.ozlabs.org; envelope-from=linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org; receiver=) Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by bilbo.ozlabs.org (Postfix) with ESMTPS id 4JdpWZ2mjKz9sRR for ; Wed, 19 Jan 2022 12:50:50 +1100 (AEDT) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4JdpWY0Fypz30Qt for ; Wed, 19 Jan 2022 12:50:49 +1100 (AEDT) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=huawei.com (client-ip=45.249.212.187; helo=szxga01-in.huawei.com; envelope-from=heying24@huawei.com; receiver=) Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4JdpWM1YYMz2yLg for ; Wed, 19 Jan 2022 12:50:34 +1100 (AEDT) Received: from dggeme758-chm.china.huawei.com (unknown [172.30.72.54]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4JdpTj2VZnzccVb; Wed, 19 Jan 2022 09:49:13 +0800 (CST) Received: from huawei.com (10.67.174.47) by dggeme758-chm.china.huawei.com (10.3.19.104) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2308.21; Wed, 19 Jan 2022 09:49:57 +0800 From: He Ying To: , , , , , , , , Subject: [PATCH] powerpc/process, kasan: Silence KASAN warnings in __get_wchan() Date: Tue, 18 Jan 2022 20:50:25 -0500 Message-ID: <20220119015025.136902-1-heying24@huawei.com> X-Mailer: git-send-email 2.17.1 MIME-Version: 1.0 X-Originating-IP: [10.67.174.47] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggeme758-chm.china.huawei.com (10.3.19.104) X-CFilter-Loop: Reflected X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, heying24@huawei.com Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" The following KASAN warning was reported in our kernel. BUG: KASAN: stack-out-of-bounds in get_wchan+0x188/0x250 Read of size 4 at addr d216f958 by task ps/14437 CPU: 3 PID: 14437 Comm: ps Tainted: G O 5.10.0 #1 Call Trace: [daa63858] [c0654348] dump_stack+0x9c/0xe4 (unreliable) [daa63888] [c035cf0c] print_address_description.constprop.3+0x8c/0x570 [daa63908] [c035d6bc] kasan_report+0x1ac/0x218 [daa63948] [c00496e8] get_wchan+0x188/0x250 [daa63978] [c0461ec8] do_task_stat+0xce8/0xe60 [daa63b98] [c0455ac8] proc_single_show+0x98/0x170 [daa63bc8] [c03cab8c] seq_read_iter+0x1ec/0x900 [daa63c38] [c03cb47c] seq_read+0x1dc/0x290 [daa63d68] [c037fc94] vfs_read+0x164/0x510 [daa63ea8] [c03808e4] ksys_read+0x144/0x1d0 [daa63f38] [c005b1dc] ret_from_syscall+0x0/0x38 --- interrupt: c00 at 0x8fa8f4 LR = 0x8fa8cc The buggy address belongs to the page: page:98ebcdd2 refcount:0 mapcount:0 mapping:00000000 index:0x2 pfn:0x1216f flags: 0x0() raw: 00000000 00000000 01010122 00000000 00000002 00000000 ffffffff 00000000 raw: 00000000 page dumped because: kasan: bad access detected Memory state around the buggy address: d216f800: 00 00 00 00 00 f1 f1 f1 f1 00 00 00 00 00 00 00 d216f880: f2 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >d216f900: 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 ^ d216f980: f2 f2 f2 f2 f2 f2 f2 00 00 00 00 00 00 00 00 00 d216fa00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 After looking into this issue, I find the buggy address belongs to the task stack region. It seems KASAN has something wrong. I look into the code of __get_wchan in x86 architecture and find the same issue has been resolved by the commit f7d27c35ddff ("x86/mm, kasan: Silence KASAN warnings in get_wchan()"). The solution could be applied to powerpc architecture too. As Andrey Ryabinin said, get_wchan() is racy by design, it may access volatile stack of running task, thus it may access redzone in a stack frame and cause KASAN to warn about this. Use READ_ONCE_NOCHECK() to silence these warnings. Signed-off-by: He Ying Reviewed-by: Kees Cook --- arch/powerpc/kernel/process.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 984813a4d5dc..a75d20f23dac 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -2160,12 +2160,12 @@ static unsigned long ___get_wchan(struct task_struct *p) return 0; do { - sp = *(unsigned long *)sp; + sp = READ_ONCE_NOCHECK(*(unsigned long *)sp); if (!validate_sp(sp, p, STACK_FRAME_OVERHEAD) || task_is_running(p)) return 0; if (count > 0) { - ip = ((unsigned long *)sp)[STACK_FRAME_LR_SAVE]; + ip = READ_ONCE_NOCHECK(((unsigned long *)sp)[STACK_FRAME_LR_SAVE]); if (!in_sched_functions(ip)) return ip; }