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From:   Catherine Hoang <catherine.hoang@oracle.com>
To:     "Darrick J. Wong" <djwong@kernel.org>
CC:     "tytso@mit.edu" <tytso@mit.edu>,
        "linux-ext4@vger.kernel.org" <linux-ext4@vger.kernel.org>
Subject: Re: [PATCH 1/2] ext4: dont return EINVAL from GETFSUUID when
 reporting UUID length
Thread-Topic: [PATCH 1/2] ext4: dont return EINVAL from GETFSUUID when
 reporting UUID length
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Date:   Fri, 11 Nov 2022 01:11:45 +0000
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> On Nov 10, 2022, at 12:16 PM, Darrick J. Wong <djwong@kernel.org> wrote:
>=20
> From: Darrick J. Wong <djwong@kernel.org>
>=20
> If userspace calls this ioctl with fsu_length (the length of the
> fsuuid.fsu_uuid array) set to zero, ext4 copies the desired uuid length
> out to userspace.  The kernel call returned a result from a valid input,
> so the return value here should be zero, not EINVAL.
>=20
> While we're at it, fix the copy_to_user call to make it clear that we're
> only copying out fsu_len.
>=20
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>

Looks good
Reviewed-by: Catherine Hoang <catherine.hoang@oracle.com>
> ---
> fs/ext4/ioctl.c |    5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>=20
>=20
> diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
> index 95dfea28bf4e..5f91f3ad3e50 100644
> --- a/fs/ext4/ioctl.c
> +++ b/fs/ext4/ioctl.c
> @@ -1153,9 +1153,10 @@ static int ext4_ioctl_getuuid(struct ext4_sb_info =
*sbi,
>=20
> 	if (fsuuid.fsu_len =3D=3D 0) {
> 		fsuuid.fsu_len =3D UUID_SIZE;
> -		if (copy_to_user(ufsuuid, &fsuuid, sizeof(fsuuid.fsu_len)))
> +		if (copy_to_user(&ufsuuid->fsu_len, &fsuuid.fsu_len,
> +					sizeof(fsuuid.fsu_len)))
> 			return -EFAULT;
> -		return -EINVAL;
> +		return 0;
> 	}
>=20
> 	if (fsuuid.fsu_len !=3D UUID_SIZE || fsuuid.fsu_flags !=3D 0)
>=20