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Message-Id: <20200623172327.5701-10-kristen@linux.intel.com>
Date: Tue, 23 Jun 2020 10:23:26 -0700
From: Kristen Carlson Accardi <kristen@...ux.intel.com>
To: keescook@...omium.org, tglx@...utronix.de, mingo@...hat.com,
bp@...en8.de
Cc: arjan@...ux.intel.com, x86@...nel.org,
linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com,
rick.p.edgecombe@...el.com,
Kristen Carlson Accardi <kristen@...ux.intel.com>,
Tony Luck <tony.luck@...el.com>
Subject: [PATCH v3 09/10] kallsyms: Hide layout
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 <kristen@...ux.intel.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
Tested-by: Tony Luck <tony.luck@...el.com>
---
kernel/kallsyms.c | 128 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 128 insertions(+)
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 16c8c605f4b0..df2b20e1b7f2 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -25,6 +25,7 @@
#include <linux/filter.h>
#include <linux/ftrace.h>
#include <linux/compiler.h>
+#include <linux/list_sort.h>
/*
* 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 +666,127 @@ 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;
+}
+
+#if defined(CONFIG_FG_KASLR)
+/*
+ * 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.
+ */
+static int kallsyms_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;
+}
+#else
static int kallsyms_open(struct inode *inode, struct file *file)
{
/*
@@ -676,6 +803,7 @@ static int kallsyms_open(struct inode *inode, struct file *file)
iter->show_value = kallsyms_show_value();
return 0;
}
+#endif /* CONFIG_FG_KASLR */
#ifdef CONFIG_KGDB_KDB
const char *kdb_walk_kallsyms(loff_t *pos)
--
2.20.1
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