[PATCH v3 2/3] Teach SELinux about anonymous inodes
From: Daniel Colascione <hidden>
Date: 2020-03-26 18:15:25
Also in:
kvm, linux-fsdevel, lkml, selinux
Subsystem:
selinux security module, the rest · Maintainers:
Paul Moore, Stephen Smalley, Linus Torvalds
This change uses the anon_inodes and LSM infrastructure introduced in
the previous patch to give SELinux the ability to control
anonymous-inode files that are created using the new _secure()
anon_inodes functions.
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 <redacted>
---
security/selinux/hooks.c | 54 +++++++++++++++++++++++++++++
security/selinux/include/classmap.h | 2 ++
2 files changed, 56 insertions(+)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 1659b59fb5d7..b9eb45c2e4e5 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c@@ -2915,6 +2915,59 @@ 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 file_operations *fops, + 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_state.initialized)) + 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); + isec->sclass = context_isec->sclass; + isec->sid = context_isec->sid; + } else { + isec->sclass = SECCLASS_ANON_INODE; + rc = security_transition_sid( + &selinux_state, tsec->sid, tsec->sid, + SECCLASS_FILE, name, &isec->sid); + if (rc) + return rc; + } + + isec->initialized = LABEL_INITIALIZED; + + /* + * Now that we've initialized security, check whether we're + * allowed to actually create this type of anonymous inode. + */ + + ad.type = LSM_AUDIT_DATA_INODE; + ad.u.inode = inode; + + return avc_has_perm(&selinux_state, + tsec->sid, + isec->sid, + isec->sclass, + FILE__CREATE, + &ad); +} + static int selinux_inode_create(struct inode *dir, struct dentry *dentry, umode_t mode) { return may_create(dir, dentry, SECCLASS_FILE);
@@ -6923,6 +6976,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(inode_free_security, selinux_inode_free_security), LSM_HOOK_INIT(inode_init_security, selinux_inode_init_security), + LSM_HOOK_INIT(inode_init_security_anon, selinux_inode_init_security_anon), LSM_HOOK_INIT(inode_create, selinux_inode_create), LSM_HOOK_INIT(inode_link, selinux_inode_link), LSM_HOOK_INIT(inode_unlink, selinux_inode_unlink),
diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h
index 986f3ac14282..263750b6aaac 100644
--- a/security/selinux/include/classmap.h
+++ b/security/selinux/include/classmap.h@@ -248,6 +248,8 @@ struct security_class_mapping secclass_map[] = { {"open", "cpu", "kernel", "tracepoint", "read", "write"} }, { "lockdown", { "integrity", "confidentiality", NULL } }, + { "anon_inode", + { COMMON_FILE_PERMS, NULL } }, { NULL } };
--
2.25.1.696.g5e7596f4ac-goog