From: Scott Mayhew <smayhew@redhat.com>
To: Paul Moore <paul@paul-moore.com>
Cc: selinux@vger.kernel.org, linux-nfs@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH RFC v2 1/2] selinux: Fix selinux_sb_mnt_opts_compat()
Date: Tue, 25 Jan 2022 13:51:51 -0500 [thread overview]
Message-ID: <YfBGx+M9jQZa80rZ@aion.usersys.redhat.com> (raw)
In-Reply-To: <CAHC9VhTwXUE9dYBHrkA3Xkr=AgXvcnfSzLLBJ4QqYd4R+kFbbA@mail.gmail.com>
On Tue, 25 Jan 2022, Paul Moore wrote:
> On Tue, Jan 25, 2022 at 12:31 PM Scott Mayhew <smayhew@redhat.com> wrote:
> > On Mon, 24 Jan 2022, Paul Moore wrote:
> > > On Thu, Jan 20, 2022 at 4:50 PM Scott Mayhew <smayhew@redhat.com> 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@redhat.com>
> > > > ---
> > > > 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.
-Scott
>
> Thanks.
>
> --
> paul moore
> paul-moore.com
>
next prev parent reply other threads:[~2022-01-25 18:52 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-20 21:49 [PATCH RFC v2 0/2] selinux: parse sids earlier to avoid doing memory allocations under spinlock Scott Mayhew
2022-01-20 21:49 ` [PATCH RFC v2 1/2] selinux: Fix selinux_sb_mnt_opts_compat() Scott Mayhew
2022-01-24 21:27 ` Paul Moore
2022-01-25 17:30 ` Scott Mayhew
2022-01-25 17:45 ` Paul Moore
2022-01-25 18:51 ` Scott Mayhew [this message]
2022-01-25 22:32 ` Paul Moore
2022-01-26 20:41 ` Scott Mayhew
2022-01-28 1:53 ` Paul Moore
2022-01-27 9:54 ` Ondrej Mosnacek
2022-01-28 2:25 ` Paul Moore
2022-01-31 12:46 ` Ondrej Mosnacek
2022-01-31 16:16 ` Paul Moore
2022-02-01 14:38 ` Ondrej Mosnacek
2022-02-01 16:19 ` Paul Moore
2022-01-20 21:49 ` [PATCH RFC v2 2/2] selinux: try to use preparsed sid before calling parse_sid() Scott Mayhew
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