From patchwork Mon Dec 4 14:27:09 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jinbum Park X-Patchwork-Id: 10090549 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id CB6CD6056E for ; Mon, 4 Dec 2017 14:42:48 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id CF8B528D8B for ; Mon, 4 Dec 2017 14:42:48 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id C46D328D8E; Mon, 4 Dec 2017 14:42:48 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED, DKIM_VALID, FREEMAIL_FROM, RCVD_IN_DNSWL_MED autolearn=unavailable version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [65.50.211.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id BAD0B28D8B for ; Mon, 4 Dec 2017 14:42:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-ID:Subject:To:From :Date:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=kHF6btVn2SsIuypsVV53xVNZ565rJ/a4aFBpc87uyqc=; b=FeitVzOSz6TUJL iKKtDTxewNCWYN65mo2Nm2rrhogJUU4K5xEAgzRMD/zgvfO9hmIWqaYImZG5/QDSkhQQDYf3m5ytd HwZPwMokeENTcl/rJ8+9bFIKNEQdOVa/lThQy8Z9MvEpYaCq+2W/EKwMpNoC8dt9jYfjhpPX2aRtF qoWmJF3uKIf6Ky0K8IiBq0ubcaHlD3QAxNqUsCSd7YF6mFjCSHfLtmcYmPZ9dosbo+Ekq8rTFTBH9 MdhzJg0xjAXVYhJwE2lG2tC1V2mre0eM107otH9qk6nhn9yjI1RM4PTFVsOcMKoQEr0KXRchNNr5M aLamkG/W/+Dxtc0lQ4CA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1eLrxG-0003fe-Kt; Mon, 04 Dec 2017 14:42:46 +0000 Received: from casper.infradead.org ([2001:8b0:10b:1236::1]) by bombadil.infradead.org with esmtps (Exim 4.87 #1 (Red Hat Linux)) id 1eLrx3-0003MJ-Cl for linux-arm-kernel@bombadil.infradead.org; Mon, 04 Dec 2017 14:42:33 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=Content-Type:MIME-Version:Message-ID: Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:In-Reply-To:References:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=s0lKnbpcvENTox9p6ppSgLcdzGeIgDC6jOxprWPwMcU=; b=fNqqSuE5xOBapzzpmtXTu2bqyD Kf8MfWRJVlLjw7zLp0Ll0HDSygKJToYGgKBVMBjMHoqfEyxeIozkNWEMFMHBbGbTSbqIWS0QHGYpD hYkPnoK28uAX0gleZVo45Up2Hj/wusuh/on+NCdbt6hOEizR/BgdflSu9Ac2jNjCZZhqyitvK0+0j 0Q4WyTwnUSti+PUY2bjaS4L07fR5dkOCyqbRzfWkK5h+ImAIWablind1rO3m6ejbDD56yBj0yh5ep sljpBW7t6FMcaJ0Mz4kh5K4KO9tXv28y63OQu4oh9ogArvU+BabPKgIsfgrg0bYtBtj4IGIPmQpoN 7n7Ljzhg==; Received: from mail-pg0-x241.google.com ([2607:f8b0:400e:c05::241]) by casper.infradead.org with esmtps (Exim 4.87 #1 (Red Hat Linux)) id 1eLric-0003wA-DK for linux-arm-kernel@lists.infradead.org; Mon, 04 Dec 2017 14:27:40 +0000 Received: by mail-pg0-x241.google.com with SMTP id j4so8303476pgp.1 for ; Mon, 04 Dec 2017 06:27:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:mime-version:content-disposition :user-agent; bh=s0lKnbpcvENTox9p6ppSgLcdzGeIgDC6jOxprWPwMcU=; b=TJ2khB4z6m8AVkKzbwYyTLnPfY9NMKM+13r4NWHusIptLxt+C4HrDMw3OM3+hwxYcQ +FMTNBbOEqthEqZOfKrokShrRwzBC/+Ukv+t3gQYnGbjbPiYBUvIYk/iSf+w2pdQuJwz fZFxIhn08pL2V8uSuwMzObwsL6GzbWtQsRkL68NUA9eYqBxebVgrUoMUJHjzZVMir0QG dwRGL7JV73I9mY/I7rPtCD/ByQoVMrQvUArYx2vqLomDayQLX98CXmi9SLbs91acbbRK QNA6C04TyBylSmpMpiu5W/O0YIvz5u1S0YjPC5lJBOWXE1YvdUIZxTN/4JJVDW1mjPKR JQ0A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:mime-version :content-disposition:user-agent; bh=s0lKnbpcvENTox9p6ppSgLcdzGeIgDC6jOxprWPwMcU=; b=J7QtFi32APMLaZQmsStnKS21Gh7hJGdvQEVAff6I/64wf9vF92LUOsMCviUE0zsUjC jA6ke3u601xM5I8m7bqMY5z2LLU6femfNr/ABK3hUY+D7rM0tmm0/pKkjrs5nk69DyIa wh97v9ZQ6Z8SI3K298AxEG0J+rOSelbnVLMchPMupNFYCIQUTRtW0oH2C61WQSUSgnBM zJ7pno/NZRGB/OCnKfRY7LhK1uPTowgPNWMh6LGS6gFspXPu1VVUdzSK3AT5QuPiJ0lt EsJYh1KcEXLVumA3whBlGyHA1ycifVhsmtsO2e+Um2+q6h+T55lB7oYtcyDTJ5OzrU5m bfig== X-Gm-Message-State: AJaThX6jFlA2LVaKOH1ORtPBc5Pr9eldEIUgoXYtoOp+uhjrDbL42FFf ISyCuDxpb66ccy4Li6iblfAWnQ== X-Google-Smtp-Source: AGs4zMZRfP5WgD/FP3QQ2PQ2+ymEQMJ53SeVMIh/BAdUOvK3V+/Na12eC8Uk6KUgqO+RP14G/b9KMA== X-Received: by 10.101.69.141 with SMTP id o13mr14392718pgq.125.1512397636174; Mon, 04 Dec 2017 06:27:16 -0800 (PST) Received: from pjb1027-Latitude-E5410 ([58.227.15.43]) by smtp.gmail.com with ESMTPSA id s81sm26386979pfg.60.2017.12.04.06.27.12 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Mon, 04 Dec 2017 06:27:15 -0800 (PST) Date: Mon, 4 Dec 2017 23:27:09 +0900 From: Jinbum Park To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com Subject: [kernel-hardening][PATCH v3 3/3] arm: mm: dump: add checking for writable and executable pages Message-ID: <20171204142709.GA3376@pjb1027-Latitude-E5410> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20171204_142738_598831_43705C7B X-CRM114-Status: GOOD ( 23.56 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, vladimir.murzin@arm.com, keescook@chromium.org, arnd@arndb.de, gregkh@linuxfoundation.org, linux@armlinux.org.uk, labbott@redhat.com, afzal.mohd.ma@gmail.com Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Page mappings with full RWX permissions are a security risk. x86, arm64 has an option to walk the page tables and dump any bad pages. (1404d6f13e47 ("arm64: dump: Add checking for writable and exectuable pages")) Add a similar implementation for arm. Signed-off-by: Jinbum Park --- v3: Reuse pg_level, prot_bits to check ro, nx prot. arch/arm/Kconfig.debug | 27 +++++++++++++++++++++++ arch/arm/include/asm/ptdump.h | 8 +++++++ arch/arm/mm/dump.c | 51 +++++++++++++++++++++++++++++++++++++++++++ arch/arm/mm/init.c | 2 ++ 4 files changed, 88 insertions(+) diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug index e7b94db..78a6470 100644 --- a/arch/arm/Kconfig.debug +++ b/arch/arm/Kconfig.debug @@ -20,6 +20,33 @@ config ARM_PTDUMP_DEBUGFS kernel. If in doubt, say "N" +config DEBUG_WX + bool "Warn on W+X mappings at boot" + select ARM_PTDUMP_CORE + ---help--- + Generate a warning if any W+X mappings are found at boot. + + This is useful for discovering cases where the kernel is leaving + W+X mappings after applying NX, as such mappings are a security risk. + + Look for a message in dmesg output like this: + + arm/mm: Checked W+X mappings: passed, no W+X pages found. + + or like this, if the check failed: + + arm/mm: Checked W+X mappings: FAILED, W+X pages found. + + Note that even if the check fails, your kernel is possibly + still fine, as W+X mappings are not a security hole in + themselves, what they do is that they make the exploitation + of other unfixed kernel bugs easier. + + There is no runtime or memory usage effect of this option + once the kernel has booted up - it's a one time check. + + If in doubt, say "Y". + # RMK wants arm kernels compiled with frame pointers or stack unwinding. # If you know what you are doing and are willing to live without stack # traces, you can get a slightly smaller kernel by setting this option to diff --git a/arch/arm/include/asm/ptdump.h b/arch/arm/include/asm/ptdump.h index 3a6c0b7..b6a0162 100644 --- a/arch/arm/include/asm/ptdump.h +++ b/arch/arm/include/asm/ptdump.h @@ -43,6 +43,14 @@ static inline int ptdump_debugfs_register(struct ptdump_info *info, } #endif /* CONFIG_ARM_PTDUMP_DEBUGFS */ +void ptdump_check_wx(void); + #endif /* CONFIG_ARM_PTDUMP_CORE */ +#ifdef CONFIG_DEBUG_WX +#define debug_checkwx() ptdump_check_wx() +#else +#define debug_checkwx() do { } while (0) +#endif + #endif /* __ASM_PTDUMP_H */ diff --git a/arch/arm/mm/dump.c b/arch/arm/mm/dump.c index 43a2bee..3e2e6f0 100644 --- a/arch/arm/mm/dump.c +++ b/arch/arm/mm/dump.c @@ -52,6 +52,8 @@ struct pg_state { unsigned long start_address; unsigned level; u64 current_prot; + bool check_wx; + unsigned long wx_pages; const char *current_domain; }; @@ -194,6 +196,8 @@ struct pg_level { const struct prot_bits *bits; size_t num; u64 mask; + const struct prot_bits *ro_bit; + const struct prot_bits *nx_bit; }; static struct pg_level pg_level[] = { @@ -203,9 +207,17 @@ struct pg_level { }, { /* pmd */ .bits = section_bits, .num = ARRAY_SIZE(section_bits), + #ifdef CONFIG_ARM_LPAE + .ro_bit = section_bits + 1, + #else + .ro_bit = section_bits, + #endif + .nx_bit = section_bits + ARRAY_SIZE(section_bits) - 2, }, { /* pte */ .bits = pte_bits, .num = ARRAY_SIZE(pte_bits), + .ro_bit = pte_bits + 1, + .nx_bit = pte_bits + 2, }, }; @@ -226,6 +238,23 @@ static void dump_prot(struct pg_state *st, const struct prot_bits *bits, size_t } } +static void note_prot_wx(struct pg_state *st, unsigned long addr) +{ + if (!st->check_wx) + return; + if ((st->current_prot & pg_level[st->level].ro_bit->mask) == + pg_level[st->level].ro_bit->val) + return; + if ((st->current_prot & pg_level[st->level].nx_bit->mask) == + pg_level[st->level].nx_bit->val) + return; + + WARN_ONCE(1, "arm/mm: Found insecure W+X mapping at address %p/%pS\n", + (void *)st->start_address, (void *)st->start_address); + + st->wx_pages += (addr - st->start_address) / PAGE_SIZE; +} + static void note_page(struct pg_state *st, unsigned long addr, unsigned int level, u64 val, const char *domain) { @@ -244,6 +273,7 @@ static void note_page(struct pg_state *st, unsigned long addr, unsigned long delta; if (st->current_prot) { + note_prot_wx(st, addr); pt_dump_seq_printf(st->seq, "0x%08lx-0x%08lx ", st->start_address, addr); @@ -367,6 +397,7 @@ void ptdump_walk_pgd(struct seq_file *m, struct ptdump_info *info) struct pg_state st = { .seq = m, .marker = info->markers, + .check_wx = false, }; walk_pgd(&st, info->mm, info->base_addr); @@ -391,6 +422,26 @@ static void ptdump_initialize(void) .base_addr = 0, }; +void ptdump_check_wx(void) +{ + struct pg_state st = { + .seq = NULL, + .marker = (struct addr_marker[]) { + { 0, NULL}, + { -1, NULL}, + }, + .check_wx = true, + }; + + walk_pgd(&st, &init_mm, 0); + note_page(&st, 0, 0, 0, NULL); + if (st.wx_pages) + pr_warn("Checked W+X mappings: FAILED, %lu W+X pages found\n", + st.wx_pages); + else + pr_info("Checked W+X mappings: passed, no W+X pages found\n"); +} + static int ptdump_init(void) { ptdump_initialize(); diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c index a1f11a7..bd6f451 100644 --- a/arch/arm/mm/init.c +++ b/arch/arm/mm/init.c @@ -36,6 +36,7 @@ #include #include #include +#include #include #include @@ -738,6 +739,7 @@ static int __mark_rodata_ro(void *unused) void mark_rodata_ro(void) { stop_machine(__mark_rodata_ro, NULL, NULL); + debug_checkwx(); } void set_kernel_text_rw(void)