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btrfs: add 32-bit compat ioctl for BTRFS_IOC_GET_SUBVOL_INFO

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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>
This commit is contained in:
Daan De Meyer 2026-05-21 07:51:13 +00:00 committed by Johannes Thumshirn
parent c2a74ed049
commit 538e5bdbc8
1 changed files with 94 additions and 13 deletions
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107
fs/btrfs/ioctl.c
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@ -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 @@ static int btrfs_ioctl_get_subvol_info(struct inode *inode, void __user *argp)
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: