> On Nov 10, 2022, at 12:05 PM, Darrick J. Wong <djwong@xxxxxxxxxx> wrote:
>
> On Wed, Nov 09, 2022 at 02:19:59PM -0800, Catherine Hoang wrote:
>> Add a new ioctl to retrieve the UUID of a mounted xfs filesystem.
>
> I think it's worth mentioning that this is the precursor to trying to
> implement SETFSUUID... but that's something for a future series, since
> changing the uuid will upset the log, and we have to figure out how to
> deal with that gracefully.
>
>> Signed-off-by: Catherine Hoang <catherine.hoang@xxxxxxxxxx>
>> ---
>> fs/xfs/xfs_ioctl.c | 32 ++++++++++++++++++++++++++++++++
>> 1 file changed, 32 insertions(+)
>>
>> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
>> index 1f783e979629..657fe058dfba 100644
>> --- a/fs/xfs/xfs_ioctl.c
>> +++ b/fs/xfs/xfs_ioctl.c
>> @@ -1865,6 +1865,35 @@ xfs_fs_eofblocks_from_user(
>> return 0;
>> }
>>
>> +static int xfs_ioctl_getuuid(
>
> Nit: function names should start on a new line.
>
Ok, will fix that
>> + struct xfs_mount *mp,
>> + struct fsuuid __user *ufsuuid)
>> +{
>> + struct fsuuid fsuuid;
>> + __u8 uuid[UUID_SIZE];
>> +
>> + if (copy_from_user(&fsuuid, ufsuuid, sizeof(fsuuid)))
>> + return -EFAULT;
>> +
>> + if (fsuuid.fsu_len == 0) {
>> + fsuuid.fsu_len = UUID_SIZE;
>> + if (copy_to_user(ufsuuid, &fsuuid, sizeof(fsuuid.fsu_len)))
>> + return -EFAULT;
>> + return -EINVAL;
>
> Ted and I were looking through the ext4_ioctl_getuuid function on this
> morning's ext4 concall, and we decided that copying the desired uuid
> buffer length out to userspace shouldn't result in an EINVAL return
> here...
>
>> + }
>> +
>> + if (fsuuid.fsu_len != UUID_SIZE || fsuuid.fsu_flags != 0)
>
> ...and that we shouldn't reject the case where fsu_len > UUID_SIZE.
> Instead, we should copy the uuid and update the caller's fsu_len to
> reflect however many bytes we copied out. I'll send patches to do that
> shortly.
Ok, that makes sense. I’ll apply those changes over to xfs. Thanks!
>
>> + return -EINVAL;
>> +
>> + spin_lock(&mp->m_sb_lock);
>> + memcpy(uuid, &mp->m_sb.sb_uuid, UUID_SIZE);
>> + spin_unlock(&mp->m_sb_lock);
>> +
>> + if (copy_to_user(&ufsuuid->fsu_uuid[0], uuid, UUID_SIZE))
>> + return -EFAULT;
>
> The rest of this logic looks correct to me. Thanks for getting this out
> there.
>
> --D
>
>> + return 0;
>> +}
>> +
>> /*
>> * These long-unused ioctls were removed from the official ioctl API in 5.17,
>> * but retain these definitions so that we can log warnings about them.
>> @@ -2153,6 +2182,9 @@ xfs_file_ioctl(
>> return error;
>> }
>>
>> + case FS_IOC_GETFSUUID:
>> + return xfs_ioctl_getuuid(mp, arg);
>> +
>> default:
>> return -ENOTTY;
>> }
>> --
>> 2.25.1
