On 12.07.2018 09:19, Qu Wenruo wrote:
> Introduce a new macro based compile time check for ioctl structures.
>
> The new macro is BTRFS_ASSERT_SIZE(), which is mostly copied from
> VMMDEV_ASSERT_SIZE().
>
> Such check is only added to structure pended to power of 2.
> And exposed one structure, btrfs_ioctl_get_dev_stats() is not aligned
> well.
> The misalign is introduced by commit b27f7c0c150f ("btrfs: join DEV_STATS
> ioctls to one").
So what's the negative effect if a structure is not aligned to a power of 2?
>
> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
> ---
> include/uapi/linux/btrfs.h | 18 +++++++++++++++++-
> 1 file changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
> index 5ca1d21fc4a7..be1213c10080 100644
> --- a/include/uapi/linux/btrfs.h
> +++ b/include/uapi/linux/btrfs.h
> @@ -22,6 +22,14 @@
> #include <linux/types.h>
> #include <linux/ioctl.h>
>
> +/*
> + * Compile time check on structure size, same method as
> + * VMMDEV_ASSERT_SIZE() from linux/vbox_vmmdev_types.h, to trigger a negative
> + * array size at compile time if size doesn't match.
> + */
> +#define BTRFS_ASSERT_SIZE(type, size) \
> + typedef char type ## _asrt_size[1 - 2 * !!(sizeof(struct type) != (size))]
> +
> #define BTRFS_IOCTL_MAGIC 0x94
> #define BTRFS_VOL_NAME_MAX 255
> #define BTRFS_LABEL_SIZE 256
> @@ -32,6 +40,7 @@ struct btrfs_ioctl_vol_args {
> __s64 fd;
> char name[BTRFS_PATH_NAME_MAX + 1];
> };
> +BTRFS_ASSERT_SIZE(btrfs_ioctl_vol_args, 4096);
>
> #define BTRFS_DEVICE_PATH_NAME_MAX 1024
> #define BTRFS_SUBVOL_NAME_MAX 4039
> @@ -171,6 +180,7 @@ struct btrfs_ioctl_scrub_args {
> /* pad to 1k */
> __u64 unused[(1024-32-sizeof(struct btrfs_scrub_progress))/8];
> };
> +BTRFS_ASSERT_SIZE(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
> @@ -223,6 +233,7 @@ struct btrfs_ioctl_dev_info_args {
> __u64 unused[379]; /* pad to 4k */
> __u8 path[BTRFS_DEVICE_PATH_NAME_MAX]; /* out */
> };
> +BTRFS_ASSERT_SIZE(btrfs_ioctl_dev_info_args, 4096);
>
> struct btrfs_ioctl_fs_info_args {
> __u64 max_id; /* out */
> @@ -234,6 +245,7 @@ struct btrfs_ioctl_fs_info_args {
> __u32 reserved32;
> __u64 reserved[122]; /* pad to 1k */
> };
> +BTRFS_ASSERT_SIZE(btrfs_ioctl_fs_info_args, 1024);
>
> /*
> * feature flags
> @@ -414,6 +426,7 @@ struct btrfs_ioctl_balance_args {
>
> __u64 unused[72]; /* pad to 1k */
> };
> +BTRFS_ASSERT_SIZE(btrfs_ioctl_balance_args, 1024);
>
> #define BTRFS_INO_LOOKUP_PATH_MAX 4080
> struct btrfs_ioctl_ino_lookup_args {
> @@ -421,6 +434,7 @@ struct btrfs_ioctl_ino_lookup_args {
> __u64 objectid;
> char name[BTRFS_INO_LOOKUP_PATH_MAX];
> };
> +BTRFS_ASSERT_SIZE(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 {
> @@ -436,6 +450,7 @@ struct btrfs_ioctl_ino_lookup_user_args {
> */
> char path[BTRFS_INO_LOOKUP_USER_PATH_MAX];
> };
> +BTRFS_ASSERT_SIZE(btrfs_ioctl_ino_lookup_args, 4096);
>
> /* Search criteria for the btrfs SEARCH ioctl family. */
> struct btrfs_ioctl_search_key {
> @@ -664,8 +679,9 @@ struct btrfs_ioctl_get_dev_stats {
> /* out values: */
> __u64 values[BTRFS_DEV_STAT_VALUES_MAX];
>
> - __u64 unused[128 - 2 - BTRFS_DEV_STAT_VALUES_MAX]; /* pad to 1k */
> + __u64 unused[128 - 3 - BTRFS_DEV_STAT_VALUES_MAX]; /* pad to 1k */
> };
> +BTRFS_ASSERT_SIZE(btrfs_ioctl_get_dev_stats, 1024);
>
> #define BTRFS_QUOTA_CTL_ENABLE 1
> #define BTRFS_QUOTA_CTL_DISABLE 2
>
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