From patchwork Tue Aug 27 08:46:20 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Wieczorkiewicz, Pawel" X-Patchwork-Id: 11116363 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 04FB71399 for ; Tue, 27 Aug 2019 08:48:21 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 C8AD4206BB for ; Tue, 27 Aug 2019 08:48:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=amazon.de header.i=@amazon.de header.b="sIRa7BaX" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C8AD4206BB Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=amazon.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1i2X8W-00030y-7r; Tue, 27 Aug 2019 08:47:32 +0000 Received: from all-amaz-eas1.inumbo.com ([34.197.232.57] helo=us1-amaz-eas2.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.89) (envelope-from ) id 1i2X8U-0002yE-MF for xen-devel@lists.xen.org; Tue, 27 Aug 2019 08:47:30 +0000 X-Inumbo-ID: 433e3aa3-c8a7-11e9-ae2f-12813bfff9fa Received: from smtp-fw-6002.amazon.com (unknown [52.95.49.90]) by us1-amaz-eas2.inumbo.com (Halon) with ESMTPS id 433e3aa3-c8a7-11e9-ae2f-12813bfff9fa; Tue, 27 Aug 2019 08:47:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.de; i=@amazon.de; q=dns/txt; s=amazon201209; t=1566895633; x=1598431633; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version; bh=YzbRxlmckMA9S6eiYKMn5PZH/NmHh5WuvM6agy/KnyA=; b=sIRa7BaXmM+C9l6iJ8kNpJLbLkE9WAdMfg6/zbsvMrqJtyWeE40aQZmV pckVuq4oF/wFuIuFpye/QDon9fq5g9QONVkHUNy40Uh2kZElkzBsz8Y+P Q0f/v0pHUSqAgclIJZrEOOZQWZoUxwlrnFcChD7+Ox5nufj+TwauRsC7/ I=; X-IronPort-AV: E=Sophos;i="5.64,436,1559520000"; d="scan'208";a="417885654" Received: from iad6-co-svc-p1-lb1-vlan3.amazon.com (HELO email-inbound-relay-1e-62350142.us-east-1.amazon.com) ([10.124.125.6]) by smtp-border-fw-out-6002.iad6.amazon.com with ESMTP; 27 Aug 2019 08:47:12 +0000 Received: from EX13MTAUEA001.ant.amazon.com (iad55-ws-svc-p15-lb9-vlan3.iad.amazon.com [10.40.159.166]) by email-inbound-relay-1e-62350142.us-east-1.amazon.com (Postfix) with ESMTPS id 2142CA1DDE; Tue, 27 Aug 2019 08:47:09 +0000 (UTC) Received: from EX13D03EUC004.ant.amazon.com (10.43.164.33) by EX13MTAUEA001.ant.amazon.com (10.43.61.82) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Tue, 27 Aug 2019 08:46:54 +0000 Received: from EX13MTAUEE001.ant.amazon.com (10.43.62.200) by EX13D03EUC004.ant.amazon.com (10.43.164.33) with Microsoft SMTP Server (TLS) id 15.0.1367.3; Tue, 27 Aug 2019 08:46:53 +0000 Received: from dev-dsk-wipawel-1a-0c4e6d58.eu-west-1.amazon.com (10.4.134.33) by mail-relay.amazon.com (10.43.62.226) with Microsoft SMTP Server id 15.0.1367.3 via Frontend Transport; Tue, 27 Aug 2019 08:46:51 +0000 From: Pawel Wieczorkiewicz To: , Date: Tue, 27 Aug 2019 08:46:20 +0000 Message-ID: <20190827084624.116917-9-wipawel@amazon.de> X-Mailer: git-send-email 2.16.5 In-Reply-To: <20190827084624.116917-1-wipawel@amazon.de> References: <20190821081931.90887-1-wipawel@amazon.de> <20190827084624.116917-1-wipawel@amazon.de> MIME-Version: 1.0 Precedence: Bulk Subject: [Xen-devel] [PATCH v2 08/12] livepatch: Add support for inline asm hotpatching expectations X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.23 List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: wipawel@amazon.com, Stefano Stabellini , Wei Liu , Konrad Rzeszutek Wilk , George Dunlap , Andrew Cooper , Ross Lagerwall , Ian Jackson , mpohlack@amazon.com, Tim Deegan , Pawel Wieczorkiewicz , Julien Grall , Jan Beulich Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" This is the initial implementation of the expectations enhancement to improve inline asm hotpatching. Expectations are designed as optional feature, since the main use of them is planned for inline asm hotpatching. The flag enabled allows to control the expectation state. Each expectation has data and len fields that describe the data that is expected to be found at a given patching (old_addr) location. The len must not exceed the data array size. The data array size follows the size of the opaque array, since the opaque array holds the original data and therefore must match what is specified in the expectation (if enabled). The payload structure is modified as each expectation structure is part of the livepatch_func structure and hence extends the payload. Each expectation is checked prior to the apply action (i.e. as late as possible to check against the most current state of the code). For the replace action a new payload's expectations are checked AFTER all applied payloads are successfully reverted, but BEFORE new payload is applied. That breaks the replace action's atomicity and in case of an expectation check failure would leave a system with all payloads reverted. That is obviously insecure. Use it with caution and act upon replace errors! Signed-off-by: Pawel Wieczorkiewicz Reviewed-by: Andra-Irina Paraschiv Reviewed-by: Martin Pohlack Reviewed-by: Norbert Manthey --- Changed since v1: * added corresponding documentation * added tests .gitignore | 1 + docs/misc/livepatch.pandoc | 28 ++++++++++++ xen/common/livepatch.c | 71 ++++++++++++++++++++++++++++++ xen/include/public/sysctl.h | 15 ++++++- xen/test/livepatch/Makefile | 27 +++++++++++- xen/test/livepatch/xen_expectations.c | 41 +++++++++++++++++ xen/test/livepatch/xen_expectations_fail.c | 42 ++++++++++++++++++ 7 files changed, 222 insertions(+), 3 deletions(-) create mode 100644 xen/test/livepatch/xen_expectations.c create mode 100644 xen/test/livepatch/xen_expectations_fail.c diff --git a/.gitignore b/.gitignore index 5b80e2bbd5..cb770cc8c7 100644 --- a/.gitignore +++ b/.gitignore @@ -308,6 +308,7 @@ xen/include/xen/acm_policy.h xen/include/xen/compile.h xen/include/xen/lib/x86/cpuid-autogen.h xen/test/livepatch/config.h +xen/test/livepatch/expect_config.h xen/test/livepatch/*.livepatch xen/tools/kconfig/.tmp_gtkcheck xen/tools/kconfig/.tmp_qtcheck diff --git a/docs/misc/livepatch.pandoc b/docs/misc/livepatch.pandoc index 6ab7f4c2d2..92a424e918 100644 --- a/docs/misc/livepatch.pandoc +++ b/docs/misc/livepatch.pandoc @@ -300,6 +300,7 @@ which describe the functions to be patched: /* Added to livepatch payload version 2: */ uint8_t applied; uint8_t _pad[7]; + livepatch_expectation_t expect; }; The size of the structure is 64 bytes on 64-bit hypervisors. It will be @@ -336,6 +337,26 @@ The version 2 of the payload adds the following fields to the structure: * `applied` tracks function's applied/reverted state. It has a boolean type either LIVEPATCH_FUNC_NOT_APPLIED or LIVEPATCH_FUNC_APPLIED. * `_pad[7]` adds padding to align to 8 bytes. + * `expect` is an optional structure containing expected to-be-replaced data + (mostly for inline asm patching). The `expect` structure format is: + + struct livepatch_expectation { + uint8_t enabled : 1; + uint8_t len : 5; + uint8_t data[LIVEPATCH_OPAQUE_SIZE]; /* Same size as opaque[] buffer of + struct livepatch_func. This is the + max number of bytes to be patched */ + }; + typedef struct livepatch_expectation livepatch_expectation_t; + + * `enabled` allows to enable the expectation check for given function. + Default state is disabled. + * `len` specifies the number of valid bytes in `data` array. 5 bits is + enough to specify values up to 32 (of bytes), which is above the array + size. + * `data` contains expected bytes of content to be replaced. Same size as + `opaque` buffer of `struct livepatch_func` (max number of bytes to be + patched). The size of the `livepatch_func` array is determined from the ELF section size. @@ -391,6 +412,7 @@ A simple example of what a payload file can be: /* Added to livepatch payload version 2: */ uint8_t applied; uint8_t _pad[7]; + livepatch_expectation_t expect; }; /* Our replacement function for xen_extra_version. */ @@ -408,6 +430,12 @@ A simple example of what a payload file can be: .old_addr = (void *)0xffff82d08013963c, /* Extracted from xen-syms. */ .new_size = 13, /* To be be computed by scripts. */ .old_size = 13, /* -----------""--------------- */ + /* Added to livepatch payload version 2: */ + .expect = { /* All fields to be filled manually */ + .enabled = 1, + .len = 5, + .data = { 0x48, 0x8d, 0x05, 0x33, 0x1C } + }, } __attribute__((__section__(".livepatch.funcs"))); Code must be compiled with `-fPIC`. diff --git a/xen/common/livepatch.c b/xen/common/livepatch.c index d76619844c..cdae324724 100644 --- a/xen/common/livepatch.c +++ b/xen/common/livepatch.c @@ -560,6 +560,58 @@ static int check_patching_sections(const struct livepatch_elf *elf) return 0; } +static inline int livepatch_verify_expectation_fn(const struct livepatch_func *func) +{ + const livepatch_expectation_t *exp = &func->expect; + + /* Ignore disabled expectations. */ + if ( !exp->enabled ) + return 0; + + /* There is nothing to expect */ + if ( !func->old_addr ) + return -EFAULT; + + if ( exp->len > sizeof(exp->data)) + return -EOVERFLOW; + + /* Incorrect expectation */ + if ( func->old_size < exp->len ) + return -ERANGE; + + if ( memcmp(func->old_addr, exp->data, exp->len) ) + { + printk(XENLOG_ERR LIVEPATCH "%s: expectation failed: expected:%*phN, actual:%*phN\n", + func->name, exp->len, exp->data, exp->len, func->old_addr); + return -EINVAL; + } + + return 0; +} + +static inline int livepatch_check_expectations(const struct payload *payload) +{ + int i, rc; + + printk(XENLOG_INFO LIVEPATCH "%s: Verifying enabled expectations for all functions\n", + payload->name); + + for ( i = 0; i < payload->nfuncs; i++ ) + { + const struct livepatch_func *func = &(payload->funcs[i]); + + rc = livepatch_verify_expectation_fn(func); + if ( rc ) + { + printk(XENLOG_ERR LIVEPATCH "%s: expectations of %s failed (rc=%d), aborting!\n", + payload->name, func->name ?: "unknown", rc); + return rc; + } + } + + return 0; +} + /* * Lookup specified section and when exists assign its address to a specified hook. * Perform section pointer and size validation: single hook sections must contain a @@ -1345,6 +1397,20 @@ static void livepatch_do_action(void) if ( rc == 0 ) { + /* + * Make sure all expectation requirements are met. + * Beware all the payloads are reverted at this point. + * If expectations are not met the system is left in a + * completely UNPATCHED state! + */ + rc = livepatch_check_expectations(data); + if ( rc ) + { + printk(XENLOG_ERR LIVEPATCH "%s: SYSTEM MIGHT BE INSECURE: " + "Replace action has been aborted after reverting ALL payloads!\n", data->name); + break; + } + if ( is_hook_enabled(data->hooks.apply.action) ) { printk(XENLOG_INFO LIVEPATCH "%s: Calling apply action hook function\n", data->name); @@ -1798,6 +1864,11 @@ static int livepatch_action(struct xen_sysctl_livepatch_action *action) break; } + /* Make sure all expectation requirements are met. */ + rc = livepatch_check_expectations(data); + if ( rc ) + break; + if ( is_hook_enabled(data->hooks.apply.pre) ) { printk(XENLOG_INFO LIVEPATCH "%s: Calling pre-apply hook function\n", data->name); diff --git a/xen/include/public/sysctl.h b/xen/include/public/sysctl.h index 3bcb892ce1..a454b86ce6 100644 --- a/xen/include/public/sysctl.h +++ b/xen/include/public/sysctl.h @@ -826,6 +826,18 @@ struct xen_sysctl_cpu_featureset { * We guard this with __XEN__ as toolstacks SHOULD not use it. */ #ifdef __XEN__ +#define LIVEPATCH_OPAQUE_SIZE 31 + +struct livepatch_expectation { + uint8_t enabled : 1; + uint8_t len : 5; /* Length of data up to LIVEPATCH_OPAQUE_SIZE + (5 bits is enough for now) */ + uint8_t data[LIVEPATCH_OPAQUE_SIZE]; /* Same size as opaque[] buffer of + struct livepatch_func. This is the + max number of bytes to be patched */ +}; +typedef struct livepatch_expectation livepatch_expectation_t; + typedef enum livepatch_func_state { LIVEPATCH_FUNC_NOT_APPLIED, LIVEPATCH_FUNC_APPLIED @@ -838,9 +850,10 @@ struct livepatch_func { uint32_t new_size; uint32_t old_size; uint8_t version; /* MUST be LIVEPATCH_PAYLOAD_VERSION. */ - uint8_t opaque[31]; + uint8_t opaque[LIVEPATCH_OPAQUE_SIZE]; uint8_t applied; uint8_t _pad[7]; + livepatch_expectation_t expect; }; typedef struct livepatch_func livepatch_func_t; #endif diff --git a/xen/test/livepatch/Makefile b/xen/test/livepatch/Makefile index 23113d3418..067861903f 100644 --- a/xen/test/livepatch/Makefile +++ b/xen/test/livepatch/Makefile @@ -27,6 +27,8 @@ LIVEPATCH_ACTION_HOOKS_NOFUNC := xen_action_hooks_nofunc.livepatch LIVEPATCH_ACTION_HOOKS_MARKER:= xen_action_hooks_marker.livepatch LIVEPATCH_ACTION_HOOKS_NOAPPLY:= xen_action_hooks_noapply.livepatch LIVEPATCH_ACTION_HOOKS_NOREVERT:= xen_action_hooks_norevert.livepatch +LIVEPATCH_EXPECTATIONS:= xen_expectations.livepatch +LIVEPATCH_EXPECTATIONS_FAIL:= xen_expectations_fail.livepatch LIVEPATCHES += $(LIVEPATCH) LIVEPATCHES += $(LIVEPATCH_BYE) @@ -40,6 +42,8 @@ LIVEPATCHES += $(LIVEPATCH_ACTION_HOOKS_NOFUNC) LIVEPATCHES += $(LIVEPATCH_ACTION_HOOKS_MARKER) LIVEPATCHES += $(LIVEPATCH_ACTION_HOOKS_NOAPPLY) LIVEPATCHES += $(LIVEPATCH_ACTION_HOOKS_NOREVERT) +LIVEPATCHES += $(LIVEPATCH_EXPECTATIONS) +LIVEPATCHES += $(LIVEPATCH_EXPECTATIONS_FAIL) LIVEPATCH_DEBUG_DIR ?= $(DEBUG_DIR)/xen-livepatch @@ -54,7 +58,7 @@ uninstall: .PHONY: clean clean:: - rm -f *.o .*.o.d *.livepatch config.h + rm -f *.o .*.o.d *.livepatch config.h expect_config.h # # To compute these values we need the binary files: xen-syms @@ -182,8 +186,27 @@ xen_actions_hooks_norevert.o: config.h $(LIVEPATCH_ACTION_HOOKS_NOREVERT): xen_action_hooks_marker.o xen_hello_world_func.o note.o xen_note.o $(LD) $(LDFLAGS) $(build_id_linker) -r -o $(LIVEPATCH_ACTION_HOOKS_NOREVERT) $^ +CODE_GET_EXPECT=$(shell objdump -d --insn-width=1 $(1) | grep -A6 -E '<'$(2)'>:' | tail -n +2 | awk 'BEGIN {printf "{"} {printf "0x%s,", $$2}' | sed 's/,$$/}/g') +.PHONY: expect_config.h +expect_config.h: EXPECT_BYTES=$(call CODE_GET_EXPECT,$(BASEDIR)/xen-syms,xen_extra_version) +expect_config.h: EXPECT_BYTES_COUNT=6 +expect_config.h: xen_expectations.o + (set -e; \ + echo "#define EXPECT_BYTES $(EXPECT_BYTES)"; \ + echo "#define EXPECT_BYTES_COUNT $(EXPECT_BYTES_COUNT)") > $@ + +xen_expectations.o: expect_config.h + +.PHONY: $(LIVEPATCH_EXPECTATIONS) +$(LIVEPATCH_EXPECTATIONS): xen_expectations.o xen_hello_world_func.o note.o xen_note.o + $(LD) $(LDFLAGS) $(build_id_linker) -r -o $(LIVEPATCH_EXPECTATIONS) $^ + +.PHONY: $(LIVEPATCH_EXPECTATIONS_FAIL) +$(LIVEPATCH_EXPECTATIONS_FAIL): xen_expectations_fail.o xen_hello_world_func.o note.o xen_note.o + $(LD) $(LDFLAGS) $(build_id_linker) -r -o $(LIVEPATCH_EXPECTATIONS_FAIL) $^ + .PHONY: livepatch livepatch: $(LIVEPATCH) $(LIVEPATCH_BYE) $(LIVEPATCH_REPLACE) $(LIVEPATCH_NOP) $(LIVEPATCH_NO_XEN_BUILDID) \ $(LIVEPATCH_PREPOST_HOOKS) $(LIVEPATCH_PREPOST_HOOKS_FAIL) $(LIVEPATCH_ACTION_HOOKS) \ $(LIVEPATCH_ACTION_HOOKS_NOFUNC) $(LIVEPATCH_ACTION_HOOKS_MARKER) $(LIVEPATCH_ACTION_HOOKS_NOAPPLY) \ - $(LIVEPATCH_ACTION_HOOKS_NOREVERT) + $(LIVEPATCH_ACTION_HOOKS_NOREVERT) $(LIVEPATCH_EXPECTATIONS) $(LIVEPATCH_EXPECTATIONS_FAIL) diff --git a/xen/test/livepatch/xen_expectations.c b/xen/test/livepatch/xen_expectations.c new file mode 100644 index 0000000000..c8175a458b --- /dev/null +++ b/xen/test/livepatch/xen_expectations.c @@ -0,0 +1,41 @@ +/* + * Copyright (c) 2019 Amazon.com, Inc. or its affiliates. All rights reserved. + * + */ + +#include "expect_config.h" +#include +#include +#include +#include +#include + +#include + +static const char livepatch_exceptions_str[] = "xen_extra_version"; +extern const char *xen_hello_world(void); + +struct livepatch_func __section(".livepatch.funcs") livepatch_exceptions = { + .version = LIVEPATCH_PAYLOAD_VERSION, + .name = livepatch_exceptions_str, + .new_addr = xen_hello_world, + .old_addr = xen_extra_version, + .new_size = EXPECT_BYTES_COUNT, + .old_size = EXPECT_BYTES_COUNT, + .expect = { + .enabled = 1, + .len = EXPECT_BYTES_COUNT, + .data = EXPECT_BYTES + }, + +}; + +/* + * Local variables: + * mode: C + * c-file-style: "BSD" + * c-basic-offset: 4 + * tab-width: 4 + * indent-tabs-mode: nil + * End: + */ diff --git a/xen/test/livepatch/xen_expectations_fail.c b/xen/test/livepatch/xen_expectations_fail.c new file mode 100644 index 0000000000..36a110286f --- /dev/null +++ b/xen/test/livepatch/xen_expectations_fail.c @@ -0,0 +1,42 @@ +/* + * Copyright (c) 2019 Amazon.com, Inc. or its affiliates. All rights reserved. + * + */ + +#include +#include +#include +#include +#include + +#include + +static const char livepatch_exceptions_str[] = "xen_extra_version"; +extern const char *xen_hello_world(void); + +#define EXPECT_BYTES_COUNT 6 + +struct livepatch_func __section(".livepatch.funcs") livepatch_exceptions = { + .version = LIVEPATCH_PAYLOAD_VERSION, + .name = livepatch_exceptions_str, + .new_addr = xen_hello_world, + .old_addr = xen_extra_version, + .new_size = EXPECT_BYTES_COUNT, + .old_size = EXPECT_BYTES_COUNT, + .expect = { + .enabled = 1, + .len = EXPECT_BYTES_COUNT, + .data = { 0xDE, 0xAD, 0xC0, 0xDE, 0xBA, 0xBE } + }, + +}; + +/* + * Local variables: + * mode: C + * c-file-style: "BSD" + * c-basic-offset: 4 + * tab-width: 4 + * indent-tabs-mode: nil + * End: + */