linux-kernel - Re: [PATCH v3] selinux: lsm: fix a missing-check bug in selinux_sb_eat_lsm

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Date:   Sat, 1 Jun 2019 10:44:59 +0800
From:   Gen Zhang <blackgod016574@...il.com>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     paul@...l-moore.com, sds@...ho.nsa.gov, eparis@...isplace.org,
        omosnace@...hat.com, selinux@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH v3] selinux: lsm: fix a missing-check bug in
 selinux_sb_eat_lsm_opts()

On Sat, Jun 01, 2019 at 03:25:27AM +0100, Al Viro wrote:
> On Sat, Jun 01, 2019 at 10:15:26AM +0800, Gen Zhang wrote:
> > In selinux_sb_eat_lsm_opts(), 'arg' is allocated by kmemdup_nul(). It
> > returns NULL when fails. So 'arg' should be checked. And 'mnt_opts' 
> > should be freed when error.
> 
> What's the latter one for?  On failure we'll get to put_fs_context()
> pretty soon, so
>         security_free_mnt_opts(&fc->security);
> will be called just fine.  Leaving it allocated on failure is fine...
Paul Moore <paul@...l-moore.com> wrote:
>It seems like we should also check for, and potentially free *mnt_opts
>as the selinux_add_opt() error handling does just below this change,
>yes?  If that is the case we might want to move that error handling
>code to the bottom of the function and jump there on error.
I am not familiar with this part. So could you please show the function
call sequence?

Thanks
Gen