[PATCH v2 4/4] btrfs: assert sizes of ioctl structures

[Johannes Thumshirn <johannes.thumshirn@xxxxxxx>]

When expanding ioctl interfaces we want to make sure we're not changing
the size of the structures, otherwise it can lead to incorrect transfers
between kernel and user-space.

Build time assert the size of each structure so we're not running into any
incompatibilities.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
---
 include/uapi/linux/btrfs.h | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index 69b88f6cb57f..d3c363398e10 100644
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -32,6 +32,7 @@ struct btrfs_ioctl_vol_args {
 	__s64 fd;
 	char name[BTRFS_PATH_NAME_MAX + 1];
 };
+static_assert(sizeof(struct btrfs_ioctl_vol_args) == 4096);
 
 #define BTRFS_DEVICE_PATH_NAME_MAX	1024
 #define BTRFS_SUBVOL_NAME_MAX 		4039
@@ -190,6 +191,7 @@ struct btrfs_ioctl_scrub_args {
 	/* pad to 1k */
 	__u64 unused[(1024-32-sizeof(struct btrfs_scrub_progress))/8];
 };
+static_assert(sizeof(struct btrfs_ioctl_scrub_args) == 1024);
 
 #define BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_ALWAYS	0
 #define BTRFS_IOCTL_DEV_REPLACE_CONT_READING_FROM_SRCDEV_MODE_AVOID	1
@@ -242,6 +244,7 @@ struct btrfs_ioctl_dev_info_args {
 	__u64 unused[379];			/* pad to 4k */
 	__u8 path[BTRFS_DEVICE_PATH_NAME_MAX];	/* out */
 };
+static_assert(sizeof(struct btrfs_ioctl_dev_info_args) == 4096);
 
 /*
  * Retrieve information about the filesystem
@@ -270,7 +273,7 @@ struct btrfs_ioctl_fs_info_args {
 	__u8 metadata_uuid[BTRFS_FSID_SIZE];	/* out */
 	__u8 reserved[944];			/* pad to 1k */
 };
-
+static_assert(sizeof(struct btrfs_ioctl_fs_info_args) == 1024);
 
 /*
  * feature flags
@@ -453,6 +456,7 @@ struct btrfs_ioctl_balance_args {
 
 	__u64 unused[72];			/* pad to 1k */
 };
+static_assert(sizeof(struct btrfs_ioctl_balance_args) == 1024);
 
 #define BTRFS_INO_LOOKUP_PATH_MAX 4080
 struct btrfs_ioctl_ino_lookup_args {
@@ -460,6 +464,7 @@ struct btrfs_ioctl_ino_lookup_args {
 	__u64 objectid;
 	char name[BTRFS_INO_LOOKUP_PATH_MAX];
 };
+static_assert(sizeof(struct btrfs_ioctl_ino_lookup_args) == 4096);
 
 #define BTRFS_INO_LOOKUP_USER_PATH_MAX (4080 - BTRFS_VOL_NAME_MAX - 1)
 struct btrfs_ioctl_ino_lookup_user_args {
@@ -475,6 +480,7 @@ struct btrfs_ioctl_ino_lookup_user_args {
 	 */
 	char path[BTRFS_INO_LOOKUP_USER_PATH_MAX];
 };
+static_assert(sizeof(struct btrfs_ioctl_ino_lookup_user_args) == 4096);
 
 /* Search criteria for the btrfs SEARCH ioctl family. */
 struct btrfs_ioctl_search_key {
@@ -553,6 +559,7 @@ struct btrfs_ioctl_search_args {
 	struct btrfs_ioctl_search_key key;
 	char buf[BTRFS_SEARCH_ARGS_BUFSIZE];
 };
+static_assert(sizeof(struct btrfs_ioctl_search_args) == 4096);
 
 struct btrfs_ioctl_search_args_v2 {
 	struct btrfs_ioctl_search_key key; /* in/out - search parameters */
@@ -710,6 +717,7 @@ struct btrfs_ioctl_get_dev_stats {
 	 */
 	__u64 unused[128 - 2 - BTRFS_DEV_STAT_VALUES_MAX];
 };
+static_assert(sizeof(struct btrfs_ioctl_get_dev_stats) == 1032);
 
 #define BTRFS_QUOTA_CTL_ENABLE	1
 #define BTRFS_QUOTA_CTL_DISABLE	2
-- 
2.26.2