btrfs: add 32-bit compat ioctl for BTRFS_IOC_GET_SUBVOL_INFO

On 64-bit kernels with 32-bit userspace, struct btrfs_ioctl_timespec is
laid out as 16 bytes (8B sec + 4B nsec + 4B trailing padding) instead of
the 12 bytes a 32-bit userspace expects, because the surrounding struct
is not packed. As a result, struct btrfs_ioctl_get_subvol_info_args has
a different size and layout in 32-bit userspace than in the 64-bit
kernel, and BTRFS_IOC_GET_SUBVOL_INFO returns garbage to 32-bit callers.

Mirror what was done for BTRFS_IOC_SET_RECEIVED_SUBVOL: add a packed
btrfs_ioctl_get_subvol_info_args_32 with btrfs_ioctl_timespec_32 fields,
define BTRFS_IOC_GET_SUBVOL_INFO_32 with that struct as the size
argument, factor the existing handler into a shared _btrfs_ioctl_get_
subvol_info() helper, and add btrfs_ioctl_get_subvol_info_32() which
fills the kernel struct and translates field-by-field into the 32-bit
struct before copy_to_user().

Signed-off-by: Daan De Meyer <daan@amutable.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index d4981d2a42d712a4ac0cfb176456663fa6101d1f..5512b32752030e161d4bdc7c23dc1283b1fbd8ca 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -83,6 +83,30 @@ struct btrfs_ioctl_received_subvol_args_32 {
 
 #define BTRFS_IOC_SET_RECEIVED_SUBVOL_32 _IOWR(BTRFS_IOCTL_MAGIC, 37, \
                                struct btrfs_ioctl_received_subvol_args_32)
+
+struct btrfs_ioctl_get_subvol_info_args_32 {
+       __u64 treeid;
+       char name[BTRFS_VOL_NAME_MAX + 1];
+       __u64 parent_id;
+       __u64 dirid;
+       __u64 generation;
+       __u64 flags;
+       __u8 uuid[BTRFS_UUID_SIZE];
+       __u8 parent_uuid[BTRFS_UUID_SIZE];
+       __u8 received_uuid[BTRFS_UUID_SIZE];
+       __u64 ctransid;
+       __u64 otransid;
+       __u64 stransid;
+       __u64 rtransid;
+       struct btrfs_ioctl_timespec_32 ctime;
+       struct btrfs_ioctl_timespec_32 otime;
+       struct btrfs_ioctl_timespec_32 stime;
+       struct btrfs_ioctl_timespec_32 rtime;
+       __u64 reserved[8];
+} __attribute__ ((__packed__));
+
+#define BTRFS_IOC_GET_SUBVOL_INFO_32 _IOR(BTRFS_IOCTL_MAGIC, 60, \
+                               struct btrfs_ioctl_get_subvol_info_args_32)
 #endif
 
 #if defined(CONFIG_64BIT) && defined(CONFIG_COMPAT)
@@ -1924,9 +1948,9 @@ static int btrfs_ioctl_ino_lookup_user(struct file *file, void __user *argp)
 }
 
 /* Get the subvolume information in BTRFS_ROOT_ITEM and BTRFS_ROOT_BACKREF */
-static int btrfs_ioctl_get_subvol_info(struct inode *inode, void __user *argp)
+static int _btrfs_ioctl_get_subvol_info(struct inode *inode,
+                                       struct btrfs_ioctl_get_subvol_info_args *subvol_info)
 {
-       struct btrfs_ioctl_get_subvol_info_args AUTO_KFREE(subvol_info);
        struct btrfs_fs_info *fs_info;
        struct btrfs_root *root;
        struct btrfs_path *path;
@@ -1942,12 +1966,6 @@ static int btrfs_ioctl_get_subvol_info(struct inode *inode, void __user *argp)
        if (!path)
                return -ENOMEM;
 
-       subvol_info = kzalloc_obj(*subvol_info);
-       if (!subvol_info) {
-               btrfs_free_path(path);
-               return -ENOMEM;
-       }
-
        fs_info = BTRFS_I(inode)->root->fs_info;
 
        /* Get root_item of inode's subvolume */
@@ -2026,11 +2044,6 @@ static int btrfs_ioctl_get_subvol_info(struct inode *inode, void __user *argp)
                }
        }
 
-       btrfs_free_path(path);
-       path = NULL;
-       if (copy_to_user(argp, subvol_info, sizeof(*subvol_info)))
-               ret = -EFAULT;
-
 out:
        btrfs_put_root(root);
 out_free:
@@ -2038,6 +2051,70 @@ out_free:
        return ret;
 }
 
+#ifdef CONFIG_64BIT
+static int btrfs_ioctl_get_subvol_info_32(struct inode *inode, void __user *argp)
+{
+       struct btrfs_ioctl_get_subvol_info_args AUTO_KFREE(subvol_info);
+       struct btrfs_ioctl_get_subvol_info_args_32 AUTO_KFREE(subvol_info_32);
+       int ret;
+
+       subvol_info = kzalloc_obj(*subvol_info);
+       if (!subvol_info)
+               return -ENOMEM;
+
+       subvol_info_32 = kzalloc_obj(*subvol_info_32);
+       if (!subvol_info_32)
+               return -ENOMEM;
+
+       ret = _btrfs_ioctl_get_subvol_info(inode, subvol_info);
+       if (ret)
+               return ret;
+
+       subvol_info_32->treeid = subvol_info->treeid;
+       memcpy(subvol_info_32->name, subvol_info->name, sizeof(subvol_info_32->name));
+       subvol_info_32->parent_id = subvol_info->parent_id;
+       subvol_info_32->dirid = subvol_info->dirid;
+       subvol_info_32->generation = subvol_info->generation;
+       subvol_info_32->flags = subvol_info->flags;
+       memcpy(subvol_info_32->uuid, subvol_info->uuid, BTRFS_UUID_SIZE);
+       memcpy(subvol_info_32->parent_uuid, subvol_info->parent_uuid, BTRFS_UUID_SIZE);
+       memcpy(subvol_info_32->received_uuid, subvol_info->received_uuid, BTRFS_UUID_SIZE);
+       subvol_info_32->ctransid = subvol_info->ctransid;
+       subvol_info_32->otransid = subvol_info->otransid;
+       subvol_info_32->stransid = subvol_info->stransid;
+       subvol_info_32->rtransid = subvol_info->rtransid;
+       subvol_info_32->ctime.sec = subvol_info->ctime.sec;
+       subvol_info_32->ctime.nsec = subvol_info->ctime.nsec;
+       subvol_info_32->otime.sec = subvol_info->otime.sec;
+       subvol_info_32->otime.nsec = subvol_info->otime.nsec;
+       subvol_info_32->stime.sec = subvol_info->stime.sec;
+       subvol_info_32->stime.nsec = subvol_info->stime.nsec;
+       subvol_info_32->rtime.sec = subvol_info->rtime.sec;
+       subvol_info_32->rtime.nsec = subvol_info->rtime.nsec;
+
+       if (copy_to_user(argp, subvol_info_32, sizeof(*subvol_info_32)))
+               ret = -EFAULT;
+
+       return ret;
+}
+#endif
+
+static int btrfs_ioctl_get_subvol_info(struct inode *inode, void __user *argp)
+{
+       struct btrfs_ioctl_get_subvol_info_args AUTO_KFREE(subvol_info);
+       int ret;
+
+       subvol_info = kzalloc_obj(*subvol_info);
+       if (!subvol_info)
+               return -ENOMEM;
+
+       ret = _btrfs_ioctl_get_subvol_info(inode, subvol_info);
+       if (!ret && copy_to_user(argp, subvol_info, sizeof(*subvol_info)))
+               ret = -EFAULT;
+
+       return ret;
+}
+
 /*
  * Return ROOT_REF information of the subvolume containing this inode
  * except the subvolume name.
@@ -5529,6 +5606,10 @@ long btrfs_ioctl(struct file *file, unsigned int
                return btrfs_ioctl_set_features(file, argp);
        case BTRFS_IOC_GET_SUBVOL_INFO:
                return btrfs_ioctl_get_subvol_info(inode, argp);
+#ifdef CONFIG_64BIT
+       case BTRFS_IOC_GET_SUBVOL_INFO_32:
+               return btrfs_ioctl_get_subvol_info_32(inode, argp);
+#endif
        case BTRFS_IOC_GET_SUBVOL_ROOTREF:
                return btrfs_ioctl_get_subvol_rootref(root, argp);
        case BTRFS_IOC_INO_LOOKUP_USER: