[PATCH 27/27] fs: make nop_mnt_idmap and invalid_mnt_idmap const

[Christian Brauner <brauner@kernel.org>]

Make both static maps const so they end up in rodata. Any attempt to
modify them now faults instead of silently corrupting the initial
idmapping.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---
 fs/mnt_idmapping.c            | 4 ++--
 include/linux/mnt_idmapping.h | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/mnt_idmapping.c b/fs/mnt_idmapping.c
index 26704eeb7318..bed57094cef0 100644
--- a/fs/mnt_idmapping.c
+++ b/fs/mnt_idmapping.c
@@ -28,7 +28,7 @@ struct mnt_idmap {
  * mapping. This means that {g,u}id 0 is mapped to {g,u}id 0, {g,u}id 1 is
  * mapped to {g,u}id 1, [...], {g,u}id 1000 to {g,u}id 1000, [...].
  */
-struct mnt_idmap nop_mnt_idmap = {
+const struct mnt_idmap nop_mnt_idmap = {
 	.count	= REFCOUNT_INIT(1),
 };
 EXPORT_SYMBOL_GPL(nop_mnt_idmap);
@@ -37,7 +37,7 @@ EXPORT_SYMBOL_GPL(nop_mnt_idmap);
  * Carries the invalid idmapping of a full 0-4294967295 {g,u}id range.
  * This means that all {g,u}ids are mapped to INVALID_VFS{G,U}ID.
  */
-struct mnt_idmap invalid_mnt_idmap = {
+const struct mnt_idmap invalid_mnt_idmap = {
 	.count	= REFCOUNT_INIT(1),
 };
 EXPORT_SYMBOL_GPL(invalid_mnt_idmap);
diff --git a/include/linux/mnt_idmapping.h b/include/linux/mnt_idmapping.h
index b445c7660040..78eeef4c2996 100644
--- a/include/linux/mnt_idmapping.h
+++ b/include/linux/mnt_idmapping.h
@@ -8,8 +8,8 @@
 struct mnt_idmap;
 struct user_namespace;
 
-extern struct mnt_idmap nop_mnt_idmap;
-extern struct mnt_idmap invalid_mnt_idmap;
+extern const struct mnt_idmap nop_mnt_idmap;
+extern const struct mnt_idmap invalid_mnt_idmap;
 extern struct user_namespace init_user_ns;
 
 typedef struct {

-- 
2.53.0