From patchwork Tue Nov 9 09:48:29 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greentime Hu X-Patchwork-Id: 12610345 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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 877C8C433F5 for ; Tue, 9 Nov 2021 09:59:02 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 52FDA610A3 for ; Tue, 9 Nov 2021 09:59:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 52FDA610A3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=sifive.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Cc:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Y4EqRQPwJ9xZX4340avK4u6C5hqwDg1CX/ur0sd+ckk=; b=2GaqC1NtrQGaFI NF6XeaPKvTwxgasYVJRiaRs96EK6CV0o+jbFFD8yjOJ5fI7edjI+sVddb81NBf/9Ph6KBjH1WFGFJ PTYqN0mnmR1+CSUJNtUB8MHR4dSlWsacI0O2J5MYuXDRy+++0KFfIHKsKpASeSp+0FCnbHSHpG3Sz zW4ICWiMep2dQcF7/QxYXqWw7edbhw8Khfjxx8PSC4h5WiQwZUHtNMNi4G1dn2JQXNzXpZhSUPX6r 8VLKqcqdN635/kinknyPoTGGePhGQjTVXy7Nq0hTmXQ9dDd3HX9hOhf2E+PbrRgXnPBS0e+761B6j DEOgTQAvx1QdTpc1gTbQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mkNu3-001NGt-2a; Tue, 09 Nov 2021 09:58:55 +0000 Received: from mail-pl1-x634.google.com ([2607:f8b0:4864:20::634]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mkNkQ-001Jcl-ME for linux-riscv@lists.infradead.org; Tue, 09 Nov 2021 09:49:00 +0000 Received: by mail-pl1-x634.google.com with SMTP id q17so7851503plr.11 for ; Tue, 09 Nov 2021 01:48:58 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sifive.com; s=google; h=from:to:subject:date:message-id:in-reply-to:references:mime-version :content-transfer-encoding; bh=Ndxq/he9Iznc1VcgPcQOTE4Tyx8zhB8G5x8otwt8U5w=; b=Bfe/bWitMMb4yDH7qpV9LaONIjcHyZvnYwV/lNtuf5KNVZ5noWDb3rJBCSDxNMDjSb swrsKbETmzXPvEXX/JpI7Mql/yGow8tr8F6OvRqxjACksheLMNzAwR2zorDQUj8GPpbX C2Mxw8Qg69tBR6SenTXxWVzfnJBB4YeHYpGCWcfWAC32feZkW2YuKZL7Ok+5bABnmdgv fHKU8Me5Z51MCCJJmc5cyaW43vUfknkzMIdw6Y4fazIRhk5p18BqXgv9KWYmFmiEn53g j7HopOsdAL890ieBL+0oHmgarJMDcm7I7Ktc2wM3tHQQcZUXE6EmdFt0u659JcaxDqf9 A2UA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=Ndxq/he9Iznc1VcgPcQOTE4Tyx8zhB8G5x8otwt8U5w=; b=0uoQMXeV5I/9UCuZSdXILsxrXfrj7nNXUIpgvFTWG3mZqKzoIT7XPe5EmMEk4Puull y2PdAX1JDDP2jvK3h76cBocAP1laKoSSJFpskSOwbEHX1ODcOCf/3q9nMdTYNXvqeqiM smp6DMY6gosyfYk/CazyiZhcXKfY7W8HUiEAwZOlR4yKXmziSXhoi5AcXKYNVoMsqx2m FqSug+Aq4eYs1Ol19JSftjLOhlsQ9CQGJeISm3JPX0YWIB39+a0aQ+uaAfqeHOBjTvLk puDABtzHCC2R/ZBBZBxTI13CycTHWa9VspsMiLPv3i/7RC+vJwmcuUrU61+E1oWAbgZB uUpg== X-Gm-Message-State: AOAM530MrcrvWb08SfzJXP3Xl33gaSRiIy23Pa17rjB0gxl7SeWOLpEX WyZSFWBH4PN4DJ1GZSSzl2wU0Q== X-Google-Smtp-Source: ABdhPJxkXcHXXXYuTfH4xGUzHj722l8C5zUPIw2yiOBlrW9DlFUPkXS/76rvydZ9eLuq0PLGMSZPJg== X-Received: by 2002:a17:90b:1c07:: with SMTP id oc7mr5646669pjb.127.1636451337525; Tue, 09 Nov 2021 01:48:57 -0800 (PST) Received: from hsinchu16.internal.sifive.com (59-124-168-89.hinet-ip.hinet.net. [59.124.168.89]) by smtp.gmail.com with ESMTPSA id cv1sm1940511pjb.48.2021.11.09.01.48.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Nov 2021 01:48:57 -0800 (PST) From: Greentime Hu To: palmer@dabbelt.com, paul.walmsley@sifive.com, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, aou@eecs.berkeley.edu Subject: [PATCH v9 17/17] riscv: Fix a kernel panic issue if $s2 is set to a specific value before entering Linux Date: Tue, 9 Nov 2021 17:48:29 +0800 Message-Id: <33b87327ad65d6c655406abd69139bd126d460e4.1636362169.git.greentime.hu@sifive.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: References: MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211109_014858_824270_949E318F X-CRM114-Status: GOOD ( 15.69 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org Panic log: [ 0.018707] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 [ 0.023060] Oops [#1] [ 0.023214] Modules linked in: [ 0.023725] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.14.0 #33 [ 0.023955] Hardware name: SiFive,FU800 (DT) [ 0.024150] epc : __vstate_save+0x1c/0x48 [ 0.024654] ra : arch_dup_task_struct+0x70/0x108 [ 0.024815] epc : ffffffff80005ad8 ra : ffffffff800035a8 sp : ffffffff81203d50 [ 0.025020] gp : ffffffff812e8290 tp : ffffffff8120bdc0 t0 : 0000000000000000 [ 0.025216] t1 : 0000000000000000 t2 : 0000000000000000 s0 : ffffffff81203d80 [ 0.025424] s1 : ffffffff8120bdc0 a0 : ffffffff8120c820 a1 : 0000000000000000 [ 0.025659] a2 : 0000000000001000 a3 : 0000000000000000 a4 : 0000000000000600 [ 0.025869] a5 : ffffffff8120cdc0 a6 : ffffffe00160b400 a7 : ffffffff80a1fe60 [ 0.026069] s2 : ffffffe0016b8000 s3 : ffffffff81204000 s4 : 0000000000004000 [ 0.026267] s5 : 0000000000000000 s6 : ffffffe0016b8000 s7 : ffffffe0016b9000 [ 0.026475] s8 : ffffffff81203ee0 s9 : 0000000000800300 s10: ffffffff812e9088 [ 0.026689] s11: ffffffd004008000 t3 : 0000000000000000 t4 : 0000000000000100 [ 0.026900] t5 : 0000000000000600 t6 : ffffffe00167bcc4 [ 0.027057] status: 8000000000000720 badaddr: 0000000000000000 cause: 000000000000000f [ 0.027344] [] __vstate_save+0x1c/0x48 [ 0.027567] [] copy_process+0x266/0x11a0 [ 0.027739] [] kernel_clone+0x90/0x2aa [ 0.027915] [] kernel_thread+0x76/0x92 [ 0.028075] [] rest_init+0x26/0xfc [ 0.028242] [] arch_call_rest_init+0x10/0x18 [ 0.028423] [] start_kernel+0x5ce/0x5fe [ 0.029188] ---[ end trace 9a59af33f7ba3df4 ]--- [ 0.029479] Kernel panic - not syncing: Attempted to kill the idle task! [ 0.029907] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]--- The NULL pointer accessing caused the kernel panic. There is a NULL pointer is because in vstate_save() function it will check (regs->status & SR_VS) == SR_VS_DIRTY and this is true, but it shouldn't be true because vector is not used here. Since vector is not used, datap won't be allocated so it is NULL. The reason why regs->status is set to a wrong value is because pt_regs->status is put in stack and it is polluted after setup_vm() called. In prologue of setup_vm(), we can observe it will save s2 to stack however s2 is meaningless here because the caller is assembly code and s2 is just some value from previous stage. The compiler will base on calling convention to save the register to stack. Then 0x80008638 in s2 is saved to stack. It might be any value. In this failure case it is 0x80008638 and it will accidentally cause SR_VS_DIRTY to call the vstate_save() function. (gdb) info addr setup_vm Symbol "setup_vm" is a function at address 0xffffffff80802c8a. (gdb) va2pa 0xffffffff80802c8a $64 = 0x80a02c8a (gdb) x/10i 0x80a02c8a 0x80a02c8a: addi sp,sp,-48 0x80a02c8c: li a3,-1 0x80a02c8e: auipc a5,0xff7fd 0x80a02c92: addi a5,a5,882 0x80a02c96: sd s0,32(sp) 0x80a02c98: sd s2,16(sp) <-- store to stack After returning from setup_vm() (gdb) x/20i 0x0000000080201138 0x80201138: mv a0,s1 0x8020113a: auipc ra,0x802 0x8020113e: jalr -1200(ra) <-- jump to setup_vm() 0x80201142: auipc a0,0xa03 (gdb) p/x $sp $70 = 0x81404000 (gdb) p/x *(struct pt_regs*)($sp-0x120) $71 = { epc = 0x0, ra = 0x0, sp = 0x0, gp = 0x0, tp = 0x0, t0 = 0x0, t1 = 0x0, t2 = 0x0, s0 = 0x0, s1 = 0x0, a0 = 0x0, a1 = 0x0, a2 = 0x0, a3 = 0x81403f90, a4 = 0x80c04000, a5 = 0x1, a6 = 0xffffffff81337000, a7 = 0x81096700, s2 = 0x81400000, s3 = 0xffffffff81200000, s4 = 0x81403fd0, s5 = 0x80a02c6c, s6 = 0x8000000000006800, s7 = 0x0, s8 = 0xfffffffffffffff3, s9 = 0x80c01000, s10 = 0x81096700, s11 = 0x82200000, t3 = 0x81404000, t4 = 0x80a02dea, t5 = 0x0, t6 = 0x82200000, status = 0x80008638, <- Wrong value in stack!!! badaddr = 0x82200000, cause = 0x0, orig_a0 = 0x80201142 } (gdb) p/x $pc $72 = 0x80201142 (gdb) p/x sizeof(struct pt_regs) $73 = 0x120 Co-developed-by: ShihPo Hung Signed-off-by: ShihPo Hung Co-developed-by: Vincent Chen Signed-off-by: Vincent Chen Signed-off-by: Greentime Hu --- arch/riscv/kernel/head.S | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S index 551afe1de85e..3f881a26527d 100644 --- a/arch/riscv/kernel/head.S +++ b/arch/riscv/kernel/head.S @@ -303,6 +303,7 @@ clear_bss_done: /* Initialize page tables and relocate to virtual addresses */ la sp, init_thread_union + THREAD_SIZE XIP_FIXUP_OFFSET sp + addi sp, sp, -PT_SIZE #ifdef CONFIG_BUILTIN_DTB la a0, __dtb_start #else @@ -320,6 +321,7 @@ clear_bss_done: la tp, init_task sw zero, TASK_TI_CPU(tp) la sp, init_thread_union + THREAD_SIZE + addi sp, sp, -PT_SIZE #ifdef CONFIG_KASAN call kasan_early_init