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Date: Fri, 8 Jan 2021 13:31:30 -0800 From: Lokesh Gidra <lokeshgidra@...gle.com> To: Stephen Smalley <stephen.smalley.work@...il.com> Cc: Paul Moore <paul@...l-moore.com>, Andrea Arcangeli <aarcange@...hat.com>, Alexander Viro <viro@...iv.linux.org.uk>, James Morris <jmorris@...ei.org>, Casey Schaufler <casey@...aufler-ca.com>, Eric Biggers <ebiggers@...nel.org>, "Serge E. Hallyn" <serge@...lyn.com>, Eric Paris <eparis@...isplace.org>, Daniel Colascione <dancol@...col.org>, Kees Cook <keescook@...omium.org>, "Eric W. Biederman" <ebiederm@...ssion.com>, KP Singh <kpsingh@...gle.com>, David Howells <dhowells@...hat.com>, Anders Roxell <anders.roxell@...aro.org>, Sami Tolvanen <samitolvanen@...gle.com>, Matthew Garrett <matthewgarrett@...gle.com>, Aaron Goidel <acgoide@...ho.nsa.gov>, Randy Dunlap <rdunlap@...radead.org>, "Joel Fernandes (Google)" <joel@...lfernandes.org>, YueHaibing <yuehaibing@...wei.com>, Christian Brauner <christian.brauner@...ntu.com>, Alexei Starovoitov <ast@...nel.org>, Alexey Budankov <alexey.budankov@...ux.intel.com>, Adrian Reber <areber@...hat.com>, Aleksa Sarai <cyphar@...har.com>, Linux FS Devel <linux-fsdevel@...r.kernel.org>, linux-kernel <linux-kernel@...r.kernel.org>, LSM List <linux-security-module@...r.kernel.org>, SElinux list <selinux@...r.kernel.org>, Kalesh Singh <kaleshsingh@...gle.com>, Calin Juravle <calin@...gle.com>, Suren Baghdasaryan <surenb@...gle.com>, Jeffrey Vander Stoep <jeffv@...gle.com>, "Cc: Android Kernel" <kernel-team@...roid.com>, "open list:MEMORY MANAGEMENT" <linux-mm@...ck.org>, Andrew Morton <akpm@...ux-foundation.org>, Christoph Hellwig <hch@...radead.org>, Daniel Colascione <dancol@...gle.com> Subject: Re: [PATCH v13 3/4] selinux: teach SELinux about anonymous inodes On Fri, Jan 8, 2021 at 1:24 PM Stephen Smalley <stephen.smalley.work@...il.com> wrote: > > On Fri, Jan 8, 2021 at 3:17 PM Lokesh Gidra <lokeshgidra@...gle.com> wrote: > > > > On Fri, Jan 8, 2021 at 11:35 AM Stephen Smalley > > <stephen.smalley.work@...il.com> wrote: > > > > > > On Wed, Jan 6, 2021 at 10:03 PM Paul Moore <paul@...l-moore.com> wrote: > > > > > > > > On Wed, Nov 11, 2020 at 8:54 PM Lokesh Gidra <lokeshgidra@...gle.com> wrote: > > > > > From: Daniel Colascione <dancol@...gle.com> > > > > > > > > > > This change uses the anon_inodes and LSM infrastructure introduced in > > > > > the previous patches to give SELinux the ability to control > > > > > anonymous-inode files that are created using the new > > > > > anon_inode_getfd_secure() function. > > > > > > > > > > A SELinux policy author detects and controls these anonymous inodes by > > > > > adding a name-based type_transition rule that assigns a new security > > > > > type to anonymous-inode files created in some domain. The name used > > > > > for the name-based transition is the name associated with the > > > > > anonymous inode for file listings --- e.g., "[userfaultfd]" or > > > > > "[perf_event]". > > > > > > > > > > Example: > > > > > > > > > > type uffd_t; > > > > > type_transition sysadm_t sysadm_t : anon_inode uffd_t "[userfaultfd]"; > > > > > allow sysadm_t uffd_t:anon_inode { create }; > > > > > > > > > > (The next patch in this series is necessary for making userfaultfd > > > > > support this new interface. The example above is just > > > > > for exposition.) > > > > > > > > > > Signed-off-by: Daniel Colascione <dancol@...gle.com> > > > > > Signed-off-by: Lokesh Gidra <lokeshgidra@...gle.com> > > > > > --- > > > > > security/selinux/hooks.c | 56 +++++++++++++++++++++++++++++ > > > > > security/selinux/include/classmap.h | 2 ++ > > > > > 2 files changed, 58 insertions(+) > > > > > > > > > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c > > > > > index 6b1826fc3658..d092aa512868 100644 > > > > > --- a/security/selinux/hooks.c > > > > > +++ b/security/selinux/hooks.c > > > > > @@ -2927,6 +2927,61 @@ static int selinux_inode_init_security(struct inode *inode, struct inode *dir, > > > > > return 0; > > > > > } > > > > > > > > > > +static int selinux_inode_init_security_anon(struct inode *inode, > > > > > + const struct qstr *name, > > > > > + const struct inode *context_inode) > > > > > +{ > > > > > + const struct task_security_struct *tsec = selinux_cred(current_cred()); > > > > > + struct common_audit_data ad; > > > > > + struct inode_security_struct *isec; > > > > > + int rc; > > > > > + > > > > > + if (unlikely(!selinux_initialized(&selinux_state))) > > > > > + return 0; > > > > > + > > > > > + isec = selinux_inode(inode); > > > > > + > > > > > + /* > > > > > + * We only get here once per ephemeral inode. The inode has > > > > > + * been initialized via inode_alloc_security but is otherwise > > > > > + * untouched. > > > > > + */ > > > > > + > > > > > + if (context_inode) { > > > > > + struct inode_security_struct *context_isec = > > > > > + selinux_inode(context_inode); > > > > > + if (context_isec->initialized != LABEL_INITIALIZED) > > > > > + return -EACCES; > > Stephen, as per your explanation below, is this check also > > problematic? I mean is it possible that /dev/kvm context_inode may not > > have its label initialized? If so, then v12 of the patch series can be > > used as is. Otherwise, I will send the next version which rollbacks > > v14 and v13, except for this check. Kindly confirm. > > The context_inode should always be initialized already. I'm not fond > though of silently returning -EACCES here. At the least we should > have a pr_err() or pr_warn() here. In reality, this could only occur > in the case of a kernel bug or memory corruption so it used to be a > candidate for WARN_ON() or BUG_ON() or similar but I know that > BUG_ON() at least is frowned upon these days. Got it. I'll add a pr_err(). Thanks a lot.
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