On Fri, 2023-02-17 at 14:51 -0500, Mimi Zohar wrote:
> On Thu, 2022-12-01 at 11:41 +0100, Roberto Sassu wrote:
> > From: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
> >
> > In preparation for removing security_old_inode_init_security(), switch to
> > security_inode_init_security().
> >
> > Extend the existing ocfs2_initxattrs() to take the
> > ocfs2_security_xattr_info structure from fs_info, and populate the
> > name/value/len triple with the first xattr provided by LSMs.
> >
> > As fs_info was not used before, ocfs2_initxattrs() can now handle the case
> > of replicating the behavior of security_old_inode_init_security(), i.e.
> > just obtaining the xattr, in addition to setting all xattrs provided by
> > LSMs.
> >
> > Supporting multiple xattrs is not currently supported where
> > security_old_inode_init_security() was called (mknod, symlink), as it
> > requires non-trivial changes that can be done at a later time. Like for
> > reiserfs, even if EVM is invoked, it will not provide an xattr (if it is
> > not the first to set it, its xattr will be discarded; if it is the first,
> > it does not have xattrs to calculate the HMAC on).
> >
> > Finally, modify the handling of the return value from
> > ocfs2_init_security_get(). As security_inode_init_security() does not
> > return -EOPNOTSUPP, remove this case and directly handle the error if the
> > return value is not zero.
> >
> > However, the previous case of receiving -EOPNOTSUPP should be still
> > taken into account, as security_inode_init_security() could return zero
> > without setting xattrs and ocfs2 would consider it as if the xattr was set.
> >
> > Instead, if security_inode_init_security() returned zero, look at the xattr
> > if it was set, and behave accordingly, i.e. set si->enable to zero to
> > notify to the functions following ocfs2_init_security_get() that the xattr
> > is not available (same as if security_old_inode_init_security() returned
> > -EOPNOTSUPP).
> >
> > Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
> > Reviewed-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
>
> My previous review missed a couple of concerns.
>
> > ---
> > fs/ocfs2/namei.c | 18 ++++++------------
> > fs/ocfs2/xattr.c | 30 ++++++++++++++++++++++++++----
> > 2 files changed, 32 insertions(+), 16 deletions(-)
> >
> > diff --git a/fs/ocfs2/namei.c b/fs/ocfs2/namei.c
> > index 05f32989bad6..55fba81cd2d1 100644
> > --- a/fs/ocfs2/namei.c
> > +++ b/fs/ocfs2/namei.c
> > @@ -242,6 +242,7 @@ static int ocfs2_mknod(struct user_namespace *mnt_userns,
> > int want_meta = 0;
> > int xattr_credits = 0;
> > struct ocfs2_security_xattr_info si = {
> > + .name = NULL,
> > .enable = 1,
> > };
> > int did_quota_inode = 0;
> > @@ -315,12 +316,8 @@ static int ocfs2_mknod(struct user_namespace *mnt_userns,
> > /* get security xattr */
> > status = ocfs2_init_security_get(inode, dir, &dentry->d_name, &si);
> > if (status) {
> > - if (status == -EOPNOTSUPP)
> > - si.enable = 0;
> > - else {
> > - mlog_errno(status);
> > - goto leave;
> > - }
>
> Although security_inode_init_security() does not return -EOPNOTSUPP,
> ocfs2_init_security_get() could. Refer to commit 8154da3d2114 ("ocfs2:
> Add incompatible flag for extended attribute"). It was added as a
> temporary solution back in 2008, so it is highly unlikely that it is
> still needed.
>
> > + mlog_errno(status);
> > + goto leave;
>
> Without the -EOPNOTSUPP test, ocfs2_mknod() would not create the inode;
> and similarly ocfs2_symlink(), below, would not create the symlink. It
> would be safer not to remove the -EOPNOTSUPP test.
>
> > }
> >
> > /* calculate meta data/clusters for setting security and acl xattr */
> > @@ -1805,6 +1802,7 @@ static int ocfs2_symlink(struct user_namespace *mnt_userns,
> > int want_clusters = 0;
> > int xattr_credits = 0;
> > struct ocfs2_security_xattr_info si = {
> > + .name = NULL,
> > .enable = 1,
> > };
> > int did_quota = 0, did_quota_inode = 0;
> > @@ -1875,12 +1873,8 @@ static int ocfs2_symlink(struct user_namespace *mnt_userns,
> > /* get security xattr */
> > status = ocfs2_init_security_get(inode, dir, &dentry->d_name, &si);
> > if (status) {
> > - if (status == -EOPNOTSUPP)
> > - si.enable = 0;
> > - else {
> > - mlog_errno(status);
> > - goto bail;
> > - }
> > + mlog_errno(status);
> > + goto bail;
> > }
> >
> > /* calculate meta data/clusters for setting security xattr */
> > diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
> > index 95d0611c5fc7..55699c573541 100644
> > --- a/fs/ocfs2/xattr.c
> > +++ b/fs/ocfs2/xattr.c
> > @@ -7259,9 +7259,21 @@ static int ocfs2_xattr_security_set(const struct xattr_handler *handler,
> > static int ocfs2_initxattrs(struct inode *inode, const struct xattr *xattr_array,
> > void *fs_info)
> > {
> > + struct ocfs2_security_xattr_info *si = fs_info;
> > const struct xattr *xattr;
> > int err = 0;
> >
> > + if (si) {
> > + si->value = kmemdup(xattr_array->value, xattr_array->value_len,
> > + GFP_KERNEL);
> > + if (!si->value)
> > + return -ENOMEM;
> > +
> > + si->name = xattr_array->name;
> > + si->value_len = xattr_array->value_len;
> > + return 0;
> > + }
> > +
> > for (xattr = xattr_array; xattr->name != NULL; xattr++) {
> > err = ocfs2_xattr_set(inode, OCFS2_XATTR_INDEX_SECURITY,
> > xattr->name, xattr->value,
> > @@ -7277,13 +7289,23 @@ int ocfs2_init_security_get(struct inode *inode,
> > const struct qstr *qstr,
> > struct ocfs2_security_xattr_info *si)
> > {
> > + int ret;
> > +
> > /* check whether ocfs2 support feature xattr */
> > if (!ocfs2_supports_xattr(OCFS2_SB(dir->i_sb)))
> > return -EOPNOTSUPP;
> > - if (si)
> > - return security_old_inode_init_security(inode, dir, qstr,
> > - &si->name, &si->value,
> > - &si->value_len);
> > + if (si) {
> > + ret = security_inode_init_security(inode, dir, qstr,
> > + &ocfs2_initxattrs, si);
>
> The "if (unlikely(IS_PRIVATE(inode))" test exists in both
> security_old_inode_init_security() and security_inode_init_security(),
> but return different values. In the former case, it returns
> -EOPNOTSUPP. In the latter case, it returns 0. The question is
> whether or not we need to be concerned about private inodes on ocfs2.
> If private inodes on ocfs2 are possible, then ocsf2_mknod() or
> ocfs2_symlink() would fail to create the inode or symlink.
Correction, previously when returning -EOPNOTSUPP for private inodes,
xattrs would not be wrriten. By returning 0 without setting si->enable
to 0, xattrs will be written.
>
> > + /*
> > + * security_inode_init_security() does not return -EOPNOTSUPP,
> > + * we have to check the xattr ourselves.
> > + */
> > + if (!ret && !si->name)
> > + si->enable = 0;
> > +
> > + return ret;
> > + }
> >
> > return security_inode_init_security(inode, dir, qstr,
> > &ocfs2_initxattrs, NULL);
>
--
thanks,
Mimi
