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References: <20230329130415.2312521-1-roberto.sassu@huaweicloud.com> <20230329130415.2312521-2-roberto.sassu@huaweicloud.com>
In-Reply-To: <20230329130415.2312521-2-roberto.sassu@huaweicloud.com>
From:   Paul Moore <paul@paul-moore.com>
Date:   Thu, 30 Mar 2023 17:15:40 -0400
Message-ID: <CAHC9VhRg7twUWXLH0xTaWc2MeSFExkGr9tJztYopzD0JEM-npw@mail.gmail.com>
Subject: Re: [PATCH v9 1/4] reiserfs: Add security prefix to xattr name in reiserfs_security_write()
To:     Roberto Sassu <roberto.sassu@huaweicloud.com>
Cc:     zohar@linux.ibm.com, dmitry.kasatkin@gmail.com, jmorris@namei.org,
        serge@hallyn.com, stephen.smalley.work@gmail.com,
        eparis@parisplace.org, casey@schaufler-ca.com,
        reiserfs-devel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org, selinux@vger.kernel.org,
        bpf@vger.kernel.org, kpsingh@kernel.org, keescook@chromium.org,
        nicolas.bouchinet@clip-os.org,
        Roberto Sassu <roberto.sassu@huawei.com>,
        stable@vger.kernel.org
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On Wed, Mar 29, 2023 at 9:05=E2=80=AFAM Roberto Sassu
<roberto.sassu@huaweicloud.com> wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
>
> Reiserfs sets a security xattr at inode creation time in two stages: firs=
t,
> it calls reiserfs_security_init() to obtain the xattr from active LSMs;
> then, it calls reiserfs_security_write() to actually write that xattr.
>
> Unfortunately, it seems there is a wrong expectation that LSMs provide th=
e
> full xattr name in the form 'security.<suffix>'. However, LSMs always
> provided just the suffix, causing reiserfs to not write the xattr at all
> (if the suffix is shorter than the prefix), or to write an xattr with the
> wrong name.
>
> Add a temporary buffer in reiserfs_security_write(), and write to it the
> full xattr name, before passing it to reiserfs_xattr_set_handle().
>
> Since the 'security.' prefix is always prepended, remove the name length
> check.
>
> Cc: stable@vger.kernel.org # v2.6.x
> Fixes: 57fe60df6241 ("reiserfs: add atomic addition of selinux attributes=
 during inode creation")
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> ---
>  fs/reiserfs/xattr_security.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/fs/reiserfs/xattr_security.c b/fs/reiserfs/xattr_security.c
> index 6bffdf9a4fd..b0c354ab113 100644
> --- a/fs/reiserfs/xattr_security.c
> +++ b/fs/reiserfs/xattr_security.c
> @@ -95,11 +95,13 @@ int reiserfs_security_write(struct reiserfs_transacti=
on_handle *th,
>                             struct inode *inode,
>                             struct reiserfs_security_handle *sec)
>  {
> +       char xattr_name[XATTR_NAME_MAX + 1];
>         int error;
> -       if (strlen(sec->name) < sizeof(XATTR_SECURITY_PREFIX))
> -               return -EINVAL;

If one really wanted to be paranoid they could verify that
'XATTR_SECURITY_PREFIX_LEN + strlen(sec->name) <=3D XATTR_NAME_MAX' and
return EINVAL, but that really shouldn't be an issue and if the
concatenation does result in a xattr name that is too big, the
snprintf() will safely truncate/managle it.

Regardless, this patch is fine with me, but it would be nice if at
least of the reiserfs/VFS folks could provide an ACK/Reviewed-by tag,
although I think we can still move forward on this without one of
those.

> -       error =3D reiserfs_xattr_set_handle(th, inode, sec->name, sec->va=
lue,
> +       snprintf(xattr_name, sizeof(xattr_name), "%s%s", XATTR_SECURITY_P=
REFIX,
> +                sec->name);
> +
> +       error =3D reiserfs_xattr_set_handle(th, inode, xattr_name, sec->v=
alue,
>                                           sec->length, XATTR_CREATE);
>         if (error =3D=3D -ENODATA || error =3D=3D -EOPNOTSUPP)
>                 error =3D 0;
> --
> 2.25.1

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