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Subject[v2 087/115] sysctl: check netns-specific registration order respected
Date
Signed-off-by: Lucian Adrian Grijincu <lucian.grijincu@gmail.com>
---
include/linux/sysctl.h | 2 +
kernel/sysctl.c | 15 ++++++++-
kernel/sysctl_check.c | 78 ++++++++++++++++++++++++++++++++++++++++++-----
3 files changed, 85 insertions(+), 10 deletions(-)

diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index bdc8c97..036d1aa 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -1128,6 +1128,8 @@ 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);
+extern int sysctl_check_netns_correspondents(struct ctl_table_header *header,
+ struct ctl_table_group *group);
#endif /* CONFIG_SYSCTL_SYSCALL_CHECK */

#endif /* __KERNEL__ */
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 9b2c05a..9e50334 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1920,6 +1920,12 @@ static struct ctl_table_header *sysctl_mkdirs(struct ctl_table_header *parent,
sysctl_write_unlock_head(parent);
parent = h;
dirs[i] = NULL; /* I'm used, don't free me */
+#ifdef CONFIG_SYSCTL_SYSCALL_CHECK
+ if (sysctl_check_netns_correspondents(parent, group)) {
+ unregister_sysctl_table(h);
+ goto err_check_netns_correspondents;
+ }
+#endif
continue;
}

@@ -1946,11 +1952,18 @@ static struct ctl_table_header *sysctl_mkdirs(struct ctl_table_header *parent,

return parent;

+#ifdef CONFIG_SYSCTL_SYSCALL_CHECK
+err_check_netns_correspondents:
+ if (__netns_corresp)
+ kmem_cache_free(sysctl_header_cachep, __netns_corresp);
+#endif
+
err_alloc_coresp:
i = nr_dirs;
err_alloc_dir:
for (i--; i >= 0; i--)
- kmem_cache_free(sysctl_header_cachep, dirs[i]);
+ if (dirs[i])
+ kmem_cache_free(sysctl_header_cachep, dirs[i]);
return NULL;

}
diff --git a/kernel/sysctl_check.c b/kernel/sysctl_check.c
index 4e0bce5..55e797a 100644
--- a/kernel/sysctl_check.c
+++ b/kernel/sysctl_check.c
@@ -63,19 +63,14 @@ int sysctl_check_table(const struct ctl_path *path,
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)
+/* Print the path from to a sysctl directory. The header must *not*
+ * point to a ctl_table_header that wraps a ctl_table array, it must
+ * be a directory. */
+static void printk_sysctl_dir(struct ctl_table_header *dir)
{
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
@@ -90,7 +85,18 @@ static void duplicate_error(struct ctl_table_header *dir,
/* Print the names in the normal path order, not reversed */
for(i--; i >= 0; i--)
printk("/%s", names[i]);
+}
+
+/*
+ * @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)
+{

+ printk(KERN_ERR "sysctl duplicate check failed: ");
+ printk_sysctl_dir(dir);
printk("/%s \n", offender);
}

@@ -150,3 +156,57 @@ int sysctl_check_duplicates(struct ctl_table_header *header)

return has_duplicates;
}
+
+/* Check whether adding this header respects the rule that no
+ * non-netns-specific directory will be registered after one with the
+ * same name, but netns-specific was registered before (and still is registered)
+ *
+ * E.g. This sequence of registrations is not valid:
+ * - non-netns-specific: /net/ipv4/
+ * - netns-specific: /net/ipv4/conf/lo
+ * - non-netns-specific: /net/ipv4/conf/
+
+ * because after first adding 'conf' as a netns specific directory,
+ * we're adding one non-netns specific.
+ *
+ * NOTE: in this example, the directory that has a netns-correspondent is 'ipv4'
+ */
+int sysctl_check_netns_correspondents(struct ctl_table_header *header,
+ struct ctl_table_group *group)
+{
+ struct ctl_table_header *netns_corresp, *h;
+ int found = 0;
+ /* we're only checking registration of non-netns paths added,
+ * because only those paths can violate the above rule. */
+ if (group->has_netns_corresp)
+ return 0;
+
+ netns_corresp = sysctl_use_netns_corresp(header->parent);
+ if (!netns_corresp)
+ return 0;
+
+ /* see if the netns_correspondent has a subdir
+ * with the same as this non-netns specific header */
+ sysctl_read_lock_head(netns_corresp);
+ list_for_each_entry(h, &netns_corresp->ctl_subdirs, ctl_entry) {
+ if (IS_ERR(sysctl_use_header(h)))
+ continue;
+ if (strcmp(header->ctl_dirname, h->ctl_dirname) == 0) {
+ sysctl_unuse_header(h);
+ found = 1;
+ break;
+ }
+ sysctl_unuse_header(h);
+ }
+ sysctl_read_unlock_head(netns_corresp);
+
+ if (!found)
+ return 0;
+
+ printk(KERN_ERR "illegal sysctl registration of non-netns-specific "
+ "directory after a netns-specific with the same name\n");
+ printk_sysctl_dir(header);
+ dump_stack();
+
+ return 1;
+}
--
1.7.5.134.g1c08b


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