[PATCH 1/2 v4] user namespace: use union in {g,u}idmap struct

From: Christian Brauner
Date: Thu Oct 19 2017 - 15:12:20 EST


- Add a struct containing two pointer to extents and wrap both the static extent
array and the struct into a union. This is done in preparation for bumping the
{g,u}idmap limits for user namespaces.
- Add brackets around anonymous union when using designated initializers to
initialize members in order to please gcc <= 4.4.

Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
---
Changelog 2017-10-19:
* kernel/user.c: Use brackets around anonymous union when using designated
initializers to initialize members. This is done to please gcc <= 4.4.
---
include/linux/user_namespace.h | 18 +++++++++++++-----
kernel/user.c | 30 ++++++++++++++++++------------
2 files changed, 31 insertions(+), 17 deletions(-)

diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h
index c18e01252346..7c83d7f6289b 100644
--- a/include/linux/user_namespace.h
+++ b/include/linux/user_namespace.h
@@ -12,13 +12,21 @@

#define UID_GID_MAP_MAX_EXTENTS 5

+struct uid_gid_extent {
+ u32 first;
+ u32 lower_first;
+ u32 count;
+};
+
struct uid_gid_map { /* 64 bytes -- 1 cache line */
u32 nr_extents;
- struct uid_gid_extent {
- u32 first;
- u32 lower_first;
- u32 count;
- } extent[UID_GID_MAP_MAX_EXTENTS];
+ union {
+ struct uid_gid_extent extent[UID_GID_MAP_MAX_EXTENTS];
+ struct {
+ struct uid_gid_extent *forward;
+ struct uid_gid_extent *reverse;
+ };
+ };
};

#define USERNS_SETGROUPS_ALLOWED 1UL
diff --git a/kernel/user.c b/kernel/user.c
index 00281add65b2..9a20acce460d 100644
--- a/kernel/user.c
+++ b/kernel/user.c
@@ -26,26 +26,32 @@
struct user_namespace init_user_ns = {
.uid_map = {
.nr_extents = 1,
- .extent[0] = {
- .first = 0,
- .lower_first = 0,
- .count = 4294967295U,
+ {
+ .extent[0] = {
+ .first = 0,
+ .lower_first = 0,
+ .count = 4294967295U,
+ },
},
},
.gid_map = {
.nr_extents = 1,
- .extent[0] = {
- .first = 0,
- .lower_first = 0,
- .count = 4294967295U,
+ {
+ .extent[0] = {
+ .first = 0,
+ .lower_first = 0,
+ .count = 4294967295U,
+ },
},
},
.projid_map = {
.nr_extents = 1,
- .extent[0] = {
- .first = 0,
- .lower_first = 0,
- .count = 4294967295U,
+ {
+ .extent[0] = {
+ .first = 0,
+ .lower_first = 0,
+ .count = 4294967295U,
+ },
},
},
.count = ATOMIC_INIT(3),
--
2.14.1