From patchwork Fri Jul 17 17:00:06 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kristen Carlson Accardi X-Patchwork-Id: 11670855 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 98F7D913 for ; Fri, 17 Jul 2020 17:02:31 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id D698420704 for ; Fri, 17 Jul 2020 17:02:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D698420704 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-19384-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 11624 invoked by uid 550); 17 Jul 2020 17:01:16 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 11440 invoked from network); 17 Jul 2020 17:01:14 -0000 IronPort-SDR: cOXCi4bBw8QeDP+JbzLZvIM0YDKbFV/wYlOijBmoPmBzn9D0Qv82p47rOs+3848Lfp/ox0e1jV Xy6hYxEUWUfA== X-IronPort-AV: E=McAfee;i="6000,8403,9685"; a="137748384" X-IronPort-AV: E=Sophos;i="5.75,362,1589266800"; d="scan'208";a="137748384" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False IronPort-SDR: d3DDxs2KwSQhMwX1wAx9jnDX4JOWDz/pHxQmfbYvuTu0b8a/PV6r1X0hw0d2NTy2Cxh4aheTWe yE3Z7UCCZONw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,362,1589266800"; d="scan'208";a="270862208" From: Kristen Carlson Accardi To: keescook@chromium.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de Cc: arjan@linux.intel.com, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com, Kristen Carlson Accardi , Tony Luck Subject: [PATCH v4 09/10] kallsyms: Hide layout Date: Fri, 17 Jul 2020 10:00:06 -0700 Message-Id: <20200717170008.5949-10-kristen@linux.intel.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200717170008.5949-1-kristen@linux.intel.com> References: <20200717170008.5949-1-kristen@linux.intel.com> MIME-Version: 1.0 This patch makes /proc/kallsyms display in a random order, rather than sorted by address in order to hide the newly randomized address layout. Signed-off-by: Kristen Carlson Accardi Reviewed-by: Tony Luck Tested-by: Tony Luck --- kernel/kallsyms.c | 163 +++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 162 insertions(+), 1 deletion(-) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index bb14e64f62a4..45d147f7f10e 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -446,6 +446,12 @@ struct kallsym_iter { int show_value; }; +struct kallsyms_shuffled_iter { + struct kallsym_iter iter; + loff_t total_syms; + loff_t shuffled_index[]; +}; + int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value, char *type, char *name) { @@ -661,7 +667,7 @@ bool kallsyms_show_value(const struct cred *cred) } } -static int kallsyms_open(struct inode *inode, struct file *file) +static int __kallsyms_open(struct inode *inode, struct file *file) { /* * We keep iterator in m->private, since normal case is to @@ -682,6 +688,161 @@ static int kallsyms_open(struct inode *inode, struct file *file) return 0; } +/* + * When function granular kaslr is enabled, we need to print out the symbols + * at random so we don't reveal the new layout. + */ +#if defined(CONFIG_FG_KASLR) +static int update_random_pos(struct kallsyms_shuffled_iter *s_iter, + loff_t pos, loff_t *new_pos) +{ + loff_t new; + + if (pos >= s_iter->total_syms) + return 0; + + new = s_iter->shuffled_index[pos]; + + /* + * normally this would be done as part of update_iter, however, + * we want to avoid triggering this in the event that new is + * zero since we don't want to blow away our pos end indicators. + */ + if (new == 0) { + s_iter->iter.name[0] = '\0'; + s_iter->iter.nameoff = get_symbol_offset(new); + s_iter->iter.pos = new; + } + + *new_pos = new; + return 1; +} + +static void *shuffled_start(struct seq_file *m, loff_t *pos) +{ + struct kallsyms_shuffled_iter *s_iter = m->private; + loff_t new_pos; + + if (!update_random_pos(s_iter, *pos, &new_pos)) + return NULL; + + return s_start(m, &new_pos); +} + +static void *shuffled_next(struct seq_file *m, void *p, loff_t *pos) +{ + struct kallsyms_shuffled_iter *s_iter = m->private; + loff_t new_pos; + + (*pos)++; + + if (!update_random_pos(s_iter, *pos, &new_pos)) + return NULL; + + if (!update_iter(m->private, new_pos)) + return NULL; + + return p; +} + +/* + * shuffle_index_list() + * Use a Fisher Yates algorithm to shuffle a list of text sections. + */ +static void shuffle_index_list(loff_t *indexes, loff_t size) +{ + int i; + unsigned int j; + loff_t temp; + + for (i = size - 1; i > 0; i--) { + /* pick a random index from 0 to i */ + get_random_bytes(&j, sizeof(j)); + j = j % (i + 1); + + temp = indexes[i]; + indexes[i] = indexes[j]; + indexes[j] = temp; + } +} + +static const struct seq_operations kallsyms_shuffled_op = { + .start = shuffled_start, + .next = shuffled_next, + .stop = s_stop, + .show = s_show +}; + +static int kallsyms_random_open(struct inode *inode, struct file *file) +{ + loff_t pos; + struct kallsyms_shuffled_iter *shuffled_iter; + struct kallsym_iter iter; + bool show_value; + + /* + * If privileged, go ahead and use the normal algorithm for + * displaying symbols + */ + show_value = kallsyms_show_value(file->f_cred); + if (show_value) + return __kallsyms_open(inode, file); + + /* + * we need to figure out how many extra symbols there are + * to print out past kallsyms_num_syms + */ + pos = kallsyms_num_syms; + reset_iter(&iter, 0); + do { + if (!update_iter(&iter, pos)) + break; + pos++; + } while (1); + + /* + * add storage space for an array of loff_t equal to the size + * of the total number of symbols we need to print + */ + shuffled_iter = __seq_open_private(file, &kallsyms_shuffled_op, + sizeof(*shuffled_iter) + + (sizeof(pos) * pos)); + if (!shuffled_iter) + return -ENOMEM; + + reset_iter(&shuffled_iter->iter, 0); + shuffled_iter->iter.show_value = show_value; + shuffled_iter->total_syms = pos; + + /* + * the existing update_iter algorithm requires that we + * are either moving along increasing pos sequentially, + * or that these values are correct. Since these values + * were discovered above, initialize our new iter so we + * can use update_iter non-sequentially. + */ + shuffled_iter->iter.pos_arch_end = iter.pos_arch_end; + shuffled_iter->iter.pos_mod_end = iter.pos_mod_end; + shuffled_iter->iter.pos_ftrace_mod_end = iter.pos_ftrace_mod_end; + + /* + * initialize the array with all possible pos values, then + * shuffle the array so that the values will display in a random + * order. + */ + for (pos = 0; pos < shuffled_iter->total_syms; pos++) + shuffled_iter->shuffled_index[pos] = pos; + + shuffle_index_list(shuffled_iter->shuffled_index, shuffled_iter->total_syms); + + return 0; +} + +#define kallsyms_open kallsyms_random_open +#else +#define kallsyms_open __kallsyms_open +#endif /* CONFIG_FG_KASLR */ + #ifdef CONFIG_KGDB_KDB const char *kdb_walk_kallsyms(loff_t *pos) {