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Subject[v2 077/115] sysctl: add duplicate entry and sanity ctl_table checks
Date
Signed-off-by: Lucian Adrian Grijincu <lucian.grijincu@gmail.com>
---
include/linux/sysctl.h | 7 ++
kernel/sysctl.c | 19 ++++++-
kernel/sysctl_check.c | 153 +++++++++++++++++++++++++++++++++++++++++++++++-
3 files changed, 177 insertions(+), 2 deletions(-)
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index b626271..22b6eb8 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -1092,6 +1092,13 @@ extern struct ctl_table_header *register_sysctl_paths(const struct ctl_path *pat
struct ctl_table *table);
extern void unregister_sysctl_table(struct ctl_table_header *table);

+#ifdef CONFIG_SYSCTL_SYSCALL_CHECK
+extern int sysctl_check_table(const struct ctl_path *path,
+ int nr_dirs,
+ struct ctl_table *table);
+extern int sysctl_check_duplicates(struct ctl_table_header *header);
+#endif /* CONFIG_SYSCTL_SYSCALL_CHECK */
+
#endif /* __KERNEL__ */

#endif /* _LINUX_SYSCTL_H */
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index cbf33b1..d777e89 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1977,8 +1977,14 @@ struct ctl_table_header *__register_sysctl_paths(struct ctl_table_group *group,
const struct ctl_path *path, struct ctl_table *table)
{
struct ctl_table_header *header;
+ int failed_duplicate_check = 0;
int nr_dirs = ctl_path_items(path);

+#ifdef CONFIG_SYSCTL_SYSCALL_CHECK
+ if (sysctl_check_table(path, nr_dirs, table))
+ return NULL;
+#endif
+
header = alloc_sysctl_header(group);
if (!header)
return NULL;
@@ -1993,9 +1999,20 @@ struct ctl_table_header *__register_sysctl_paths(struct ctl_table_group *group,
header->ctl_header_refs = 1;

sysctl_write_lock_head(header->parent);
- list_add_tail(&header->ctl_entry, &header->parent->ctl_tables);
+
+#ifdef CONFIG_SYSCTL_SYSCALL_CHECK
+ failed_duplicate_check = sysctl_check_duplicates(header);
+#endif
+ if (!failed_duplicate_check)
+ list_add_tail(&header->ctl_entry, &header->parent->ctl_tables);
+
sysctl_write_unlock_head(header->parent);

+ if (failed_duplicate_check) {
+ unregister_sysctl_table(header);
+ return NULL;
+ }
+
return header;
}

diff --git a/kernel/sysctl_check.c b/kernel/sysctl_check.c
index e9a7a58..4e0bce5 100644
--- a/kernel/sysctl_check.c
+++ b/kernel/sysctl_check.c
@@ -1 +1,152 @@
-/* will be rewritten */
+#include <linux/sysctl.h>
+#include <linux/string.h>
+
+/*
+ * @path: the path to the offender
+ * @offender is the name of a file or directory that violated some sysctl rules.
+ * @str: a message accompanying the error
+ */
+static void fail(const struct ctl_path *path,
+ const char *offender,
+ const char *str)
+{
+ printk(KERN_ERR "sysctl sanity check failed: ");
+
+ for (; path->procname; path++)
+ printk("/%s", path->procname);
+
+ if (offender)
+ printk("/%s", offender);
+
+ printk(": %s\n", str);
+}
+
+#define FAIL(str) do { fail(path, t->procname, str); error = -EINVAL;} while (0)
+
+int sysctl_check_table(const struct ctl_path *path,
+ int nr_dirs,
+ struct ctl_table *table)
+{
+ struct ctl_table *t;
+ int error = 0;
+
+ if (nr_dirs > CTL_MAXNAME - 1) {
+ fail(path, NULL, "tree too deep");
+ error = -EINVAL;
+ }
+
+ for(t = table; t->procname; t++) {
+ if ((t->proc_handler == proc_dostring) ||
+ (t->proc_handler == proc_dointvec) ||
+ (t->proc_handler == proc_dointvec_minmax) ||
+ (t->proc_handler == proc_dointvec_jiffies) ||
+ (t->proc_handler == proc_dointvec_userhz_jiffies) ||
+ (t->proc_handler == proc_dointvec_ms_jiffies) ||
+ (t->proc_handler == proc_doulongvec_minmax) ||
+ (t->proc_handler == proc_doulongvec_ms_jiffies_minmax)) {
+ if (!t->data)
+ FAIL("No data");
+ if (!t->maxlen)
+ FAIL("No maxlen");
+ }
+#ifdef CONFIG_PROC_SYSCTL
+ if (!t->proc_handler)
+ FAIL("No proc_handler");
+#endif
+ if (t->mode > 0777)
+ FAIL("bogus .mode");
+ }
+
+ if (error)
+ dump_stack();
+
+ return error;
+}
+
+
+/*
+ * @dir: the directory imediately above the offender
+ * @offender is the name of a file or directory that violated some sysctl rules.
+ */
+static void duplicate_error(struct ctl_table_header *dir,
+ const char *offender)
+{
+ const char *names[CTL_MAXNAME];
+ int i = 0;
+
+ printk(KERN_ERR "sysctl duplicate check failed: ");
+
+ for (; dir->parent; dir = dir->parent)
+ /* ctl_dirname can be NULL: netns-correspondent
+ * directories do not have a ctl_dirname. Their only
+ * pourpose is to hold the list of
+ * subdirs/subtables. They hold netns-specific
+ * information for the parent directory. */
+ if (dir->ctl_dirname) {
+ names[i] = dir->ctl_dirname;
+ i++;
+ }
+
+ /* Print the names in the normal path order, not reversed */
+ for(i--; i >= 0; i--)
+ printk("/%s", names[i]);
+
+ printk("/%s \n", offender);
+}
+
+/* is there an entry in the table with the same procname? */
+static int match(struct ctl_table *table, const char *name)
+{
+ for ( ; table->procname; table++) {
+
+ if (strcmp(table->procname, name) == 0)
+ return 1;
+ }
+ return 0;
+}
+
+
+/* Called under header->parent write lock.
+ *
+ * checks whether this header's table introduces items that have the
+ * same names as other items at the same level (other files or
+ * subdirectories of the current dir). */
+int sysctl_check_duplicates(struct ctl_table_header *header)
+{
+ int has_duplicates = 0;
+ struct ctl_table *table = header->ctl_table_arg;
+ struct ctl_table_header *dir = header->parent;
+ struct ctl_table_header *h;
+
+ list_for_each_entry(h, &dir->ctl_subdirs, ctl_entry) {
+ if (IS_ERR(sysctl_use_header(h)))
+ continue;
+
+ if (match(table, h->ctl_dirname)) {
+ has_duplicates = 1;
+ duplicate_error(dir, h->ctl_dirname);
+ }
+
+ sysctl_unuse_header(h);
+ }
+
+ list_for_each_entry(h, &dir->ctl_tables, ctl_entry) {
+ ctl_table *t;
+
+ if (IS_ERR(sysctl_use_header(h)))
+ continue;
+
+ for (t = h->ctl_table_arg; t->procname; t++) {
+ if (match(table, t->procname)) {
+ has_duplicates = 1;
+ duplicate_error(dir, t->procname);
+ }
+ }
+ sysctl_unuse_header(h);
+ }
+
+ if (has_duplicates)
+ dump_stack();
+
+ return has_duplicates;
+}
--
1.7.5.134.g1c08b


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