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dmarc=fail (p=none dis=none) header.from=chromium.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-18849-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 6034 invoked by uid 550); 21 May 2020 21:14:23 -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: Received: (qmail 6011 invoked from network); 21 May 2020 21:14:22 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=XZZ5vGtImoL01xyzR64KCWDKUfIuis772xDEHmF3ldI=; b=B1edwXeQk42Z1UZf7gfSthKXb4bIu1l9sihaGaa2vq6i4vtytY9bF5qGzoIrZtPfQZ 2fc1l3wCb6wiviHILp6lflGHUcIiulV00r1Ba3iJ7MdKuH2TB63+4Oojgy/ZExBIxvPi 9W8NbphL55tG1O+Q+rdZWeUa5k2IvGMec5tmM= 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:references :mime-version:content-disposition:in-reply-to; bh=XZZ5vGtImoL01xyzR64KCWDKUfIuis772xDEHmF3ldI=; b=sf7f4zZGM5OY3AoIQ68cHhkVsO3PsFwZGReb+7FnirDhKbgFY5rkD8cqL5tvGE9V4F p06shZRpKKBhH0KmEge3lnH+DbA7ORMoDibJfGCx8MwZgFFAORtgdxCXFEiMfAbGYL3r jKMWbPxvO8F8T84p+k8clqklz4hxrdNrRqAIPFHHTnnqwo9EBENsqd32Uj7VmZNU33Tm NiY6c975jaB4eiktvXHaoAJNEDYgLKk44JJqt9CsMCJNnaFYRhf7i0wRdy4TXh0A8lqg 7pp7pEZ3VbrmvdG+XPX5raAKHPnDrBFe+cGDD4UcUeE2GOoW9erEOCEE35btGHYVrn77 snYQ== X-Gm-Message-State: AOAM532L8Nye98AdfNM+MxcrxaCXKobUrU6aAdC6A0hzaK9cEuNbIOrl 6VsisjzLOfXnH7fBU1RDOYmq3Q== X-Google-Smtp-Source: ABdhPJz5ZgIVwn633Wd8ontnJLCwdyIuRN7Je5MIDycy8URZX6MgTMECk1Rzp83xOtKruPX7kkcYfA== X-Received: by 2002:a62:760e:: with SMTP id r14mr644628pfc.92.1590095650015; Thu, 21 May 2020 14:14:10 -0700 (PDT) Date: Thu, 21 May 2020 14:14:08 -0700 From: Kees Cook To: Kristen Carlson Accardi Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, arjan@linux.intel.com, x86@kernel.org, linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com, rick.p.edgecombe@intel.com, Tony Luck Subject: Re: [PATCH v2 8/9] kallsyms: Hide layout Message-ID: <202005211409.3C314DF@keescook> References: <20200521165641.15940-1-kristen@linux.intel.com> <20200521165641.15940-9-kristen@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200521165641.15940-9-kristen@linux.intel.com> On Thu, May 21, 2020 at 09:56:39AM -0700, Kristen Carlson Accardi wrote: > This patch makes /proc/kallsyms display alphabetically by symbol > name 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 | 138 +++++++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 137 insertions(+), 1 deletion(-) > > diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c > index 16c8c605f4b0..558963b275ec 100644 > --- a/kernel/kallsyms.c > +++ b/kernel/kallsyms.c > @@ -25,6 +25,7 @@ > #include > #include > #include > +#include > > /* > * These will be re-linked against their real values > @@ -446,6 +447,11 @@ struct kallsym_iter { > int show_value; > }; > > +struct kallsyms_iter_list { > + struct kallsym_iter iter; > + struct list_head next; > +}; > + > int __weak arch_get_kallsym(unsigned int symnum, unsigned long *value, > char *type, char *name) > { > @@ -660,6 +666,121 @@ int kallsyms_show_value(void) > } > } > > +static int sorted_show(struct seq_file *m, void *p) > +{ > + struct list_head *list = m->private; > + struct kallsyms_iter_list *iter; > + int rc; > + > + if (list_empty(list)) > + return 0; > + > + iter = list_first_entry(list, struct kallsyms_iter_list, next); > + > + m->private = iter; > + rc = s_show(m, p); > + m->private = list; > + > + list_del(&iter->next); > + kfree(iter); > + > + return rc; > +} > + > +static void *sorted_start(struct seq_file *m, loff_t *pos) > +{ > + return m->private; > +} > + > +static void *sorted_next(struct seq_file *m, void *p, loff_t *pos) > +{ > + struct list_head *list = m->private; > + > + (*pos)++; > + > + if (list_empty(list)) > + return NULL; > + > + return p; > +} > + > +static const struct seq_operations kallsyms_sorted_op = { > + .start = sorted_start, > + .next = sorted_next, > + .stop = s_stop, > + .show = sorted_show > +}; > + > +static int kallsyms_list_cmp(void *priv, struct list_head *a, > + struct list_head *b) > +{ > + struct kallsyms_iter_list *iter_a, *iter_b; > + > + iter_a = list_entry(a, struct kallsyms_iter_list, next); > + iter_b = list_entry(b, struct kallsyms_iter_list, next); > + > + return strcmp(iter_a->iter.name, iter_b->iter.name); > +} > + > +int get_all_symbol_name(void *data, const char *name, struct module *mod, > + unsigned long addr) > +{ > + unsigned long sym_pos; > + struct kallsyms_iter_list *node, *last; > + struct list_head *head = (struct list_head *)data; > + > + node = kmalloc(sizeof(*node), GFP_KERNEL); > + if (!node) > + return -ENOMEM; > + > + if (list_empty(head)) { > + sym_pos = 0; > + memset(node, 0, sizeof(*node)); > + reset_iter(&node->iter, 0); > + node->iter.show_value = kallsyms_show_value(); > + } else { > + last = list_first_entry(head, struct kallsyms_iter_list, next); > + memcpy(node, last, sizeof(*node)); > + sym_pos = last->iter.pos; > + } > + > + INIT_LIST_HEAD(&node->next); > + list_add(&node->next, head); > + > + /* > + * update_iter returns false when at end of file > + * which in this case we don't care about and can > + * safely ignore. update_iter() will increment > + * the value of iter->pos, for ksymbol_core. > + */ > + if (sym_pos >= kallsyms_num_syms) > + sym_pos++; > + > + (void)update_iter(&node->iter, sym_pos); > + > + return 0; > +} > + > +static int kallsyms_sorted_open(struct inode *inode, struct file *file) > +{ > + int ret; > + struct list_head *list; > + > + list = __seq_open_private(file, &kallsyms_sorted_op, sizeof(*list)); > + if (!list) > + return -ENOMEM; > + > + INIT_LIST_HEAD(list); > + > + ret = kallsyms_on_each_symbol(get_all_symbol_name, list); > + if (ret != 0) > + return ret; > + > + list_sort(NULL, list, kallsyms_list_cmp); > + > + return 0; > +} > + > static int kallsyms_open(struct inode *inode, struct file *file) > { > /* > @@ -704,9 +825,24 @@ static const struct proc_ops kallsyms_proc_ops = { > .proc_release = seq_release_private, > }; > > +static const struct proc_ops kallsyms_sorted_proc_ops = { > + .proc_open = kallsyms_sorted_open, > + .proc_read = seq_read, > + .proc_lseek = seq_lseek, > + .proc_release = seq_release_private, > +}; > + > static int __init kallsyms_init(void) > { > - proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops); > + /* > + * When fine grained kaslr is enabled, we need to > + * print out the symbols sorted by name rather than by > + * by address, because this reveals the randomization order. > + */ > + if (!IS_ENABLED(CONFIG_FG_KASLR)) > + proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops); > + else > + proc_create("kallsyms", 0444, NULL, &kallsyms_sorted_proc_ops); > return 0; Since this is compile-time selected, instead of the separate name and test here, how about just redefine kallsyms_open initializer instead? #ifdef CONFIG_FG_KASLR ...sorting routines... static int kallsyms_open(struct inode *inode, struct file *file) { ... sorted version ... } #else static int kallsyms_open(struct inode *inode, struct file *file) { ... normal version ... } #endif (And then just move the comment to the sorted open version.) -- Kees Cook