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 Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id B2CBCC43334 for ; Tue, 14 Jun 2022 02:05:27 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4LMWx16RGKz3cdV for ; Tue, 14 Jun 2022 12:05:25 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=DcmxRrOL; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=2604:1380:40e1:4800::1; helo=sin.source.kernel.org; envelope-from=sashal@kernel.org; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20201202 header.b=DcmxRrOL; dkim-atps=neutral Received: from sin.source.kernel.org (sin.source.kernel.org [IPv6:2604:1380:40e1:4800::1]) (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 4LMWwK4L3Mz305C for ; Tue, 14 Jun 2022 12:04:49 +1000 (AEST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 61BF9CE1763; Tue, 14 Jun 2022 02:04:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5A4D0C34114; Tue, 14 Jun 2022 02:04:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1655172284; bh=z4nS/GuBUxpX0GXkgOCIkr9OBX7vs0RMQDyx7CNotDw=; h=From:To:Cc:Subject:Date:From; b=DcmxRrOLpGVsbaypdrMeZdoNBhGkxvnexuSVZAAyK3aWzMzwP1H2ExO7/g631TJHQ fGD7WjNHRJFQuUO1I9gdg600bnEkLpQgtvHtvaYorMom7rfVPZa24LbdZhiJqaTAf7 zo8f4sgZBGn+vlXnzLP9q19zsBjX8BSSJrXgEdcTOF+Kg1LH9Qi3vl5WdxIwefFtcP BOCTcMnjDvyaLQZg0uOQrp6YXV7bNFWoL6GJyHn5jYdXno4ActluZAXXHs6b4aX4ab OcBB2Dc+99+qzZnwn1mrMKNkV0Rdl6y+Btdy8FwPvn9fQawWbJNPs7Lj7qqHrpaYB0 +YzNkRKArv3qQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH AUTOSEL 5.18 01/47] powerpc/kasan: Silence KASAN warnings in __get_wchan() Date: Mon, 13 Jun 2022 22:03:54 -0400 Message-Id: <20220614020441.1098348-1-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit 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: Sasha Levin , Kees Cook , Chen Jingwen , paulus@samba.org, Wanming Hu , linuxppc-dev@lists.ozlabs.org, He Ying Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: He Ying [ Upstream commit a1b29ba2f2c171b9bea73be993bfdf0a62d37d15 ] 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. Reported-by: Wanming Hu Signed-off-by: He Ying Signed-off-by: Chen Jingwen Reviewed-by: Kees Cook Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220121014418.155675-1-heying24@huawei.com Signed-off-by: Sasha Levin --- 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; } -- 2.35.1