On Tue, Jan 25, 2022 at 1:51 PM Scott Mayhew <smayhew@xxxxxxxxxx> wrote:
> On Tue, 25 Jan 2022, Paul Moore wrote:
> > On Tue, Jan 25, 2022 at 12:31 PM Scott Mayhew <smayhew@xxxxxxxxxx> wrote:
> > > On Mon, 24 Jan 2022, Paul Moore wrote:
> > > > On Thu, Jan 20, 2022 at 4:50 PM Scott Mayhew <smayhew@xxxxxxxxxx> wrote:
> > > > >
> > > > > selinux_sb_mnt_opts_compat() is called under the sb_lock spinlock and
> > > > > shouldn't be performing any memory allocations. Fix this by parsing the
> > > > > sids at the same time we're chopping up the security mount options
> > > > > string and then using the pre-parsed sids when doing the comparison.
> > > > >
> > > > > Fixes: cc274ae7763d ("selinux: fix sleeping function called from invalid context")
> > > > > Fixes: 69c4a42d72eb ("lsm,selinux: add new hook to compare new mount to an existing mount")
> > > > > Signed-off-by: Scott Mayhew <smayhew@xxxxxxxxxx>
> > > > > ---
> > > > > security/selinux/hooks.c | 112 ++++++++++++++++++++++++++-------------
> > > > > 1 file changed, 76 insertions(+), 36 deletions(-)
> >
> > ...
> >
> > > > > switch (token) {
> > > > > case Opt_context:
> > > > > if (opts->context || opts->defcontext)
> > > > > goto err;
> > > > > opts->context = s;
> > > > > + if (preparse_sid) {
> > > > > + rc = parse_sid(NULL, s, &sid);
> > > > > + if (rc == 0) {
> > > > > + opts->context_sid = sid;
> > > > > + opts->preparsed |= CONTEXT_MNT;
> > > > > + }
> > > > > + }
> > > >
> > > > Is there a reason why we need a dedicated sid variable as opposed to
> > > > passing opt->context_sid as the parameter? For example:
> > > >
> > > > rc = parse_sid(NULL, s, &opts->context_sid);
> > >
> > > We don't need a dedicated sid variable. Should I make similar changes
> > > in the second patch (get rid of the local sid variable in
> > > selinux_sb_remount() and the *context_sid variables in
> > > selinux_set_mnt_opts())?
> >
> > Yes please, I should have explicitly mentioned that.
>
> Actually, delayed_superblock_init() calls selinux_set_mnt_opts() with
> mnt_opts == NULL, so there would have to be a lot of checks like
>
> if (opts && opts->fscontext_sid) {
>
> in the later parts of that function, which is kind of clunky. I can
> still do it if you want though.
I might be misunderstanding your concern, but in
selinux_set_mnt_opts() all of the "opts->XXX" if-conditionals are
protected by being inside an if-statement that checks to ensure "opts"
is not NULL. Am I missing something?
--
paul-moore.com
