On Tue, Dec 07, 2021 at 03:21:21PM -0500, Stefan Berger wrote:
Implement hierarchical processing of file accesses in IMA
namespaces by
walking the list of IMA namespaces towards the init_ima_ns. This way
file accesses can be audited in an IMA namespace and also be evaluated
against the IMA policies of parent IMA namespaces.
Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
---
security/integrity/ima/ima_main.c | 29 +++++++++++++++++++++++++----
1 file changed, 25 insertions(+), 4 deletions(-)
diff --git a/security/integrity/ima/ima_main.c
b/security/integrity/ima/ima_main.c
index 2121a831f38a..e9fa46eedd27 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -200,10 +200,10 @@ void ima_file_free(struct file *file)
ima_check_last_writer(iint, inode, file);
}
-static int process_measurement(struct ima_namespace *ns,
- struct file *file, const struct cred *cred,
- u32 secid, char *buf, loff_t size, int mask,
- enum ima_hooks func)
+static int _process_measurement(struct ima_namespace *ns,
Hm, it's much more common to use double underscores then single
underscores to
__process_measurement()
reads a lot more natural to people perusing kernel code quite often.
+ struct file *file, const struct cred *cred,
+ u32 secid, char *buf, loff_t size, int mask,
+ enum ima_hooks func)
{
struct inode *inode = file_inode(file);
struct integrity_iint_cache *iint = NULL;
@@ -405,6 +405,27 @@ static int process_measurement(struct
ima_namespace *ns,
return 0;
}
+static int process_measurement(struct ima_namespace *ns,
+ struct file *file, const struct cred *cred,
+ u32 secid, char *buf, loff_t size, int mask,
+ enum ima_hooks func)
+{
+ int ret = 0;
+ struct user_namespace *user_ns;
+
+ do {
+ ret = _process_measurement(ns, file, cred, secid, buf,
size, mask, func);
+ if (ret)
+ break;
+ user_ns = ns->user_ns->parent;
+ if (!user_ns)
+ break;
+ ns = user_ns->ima_ns;
+ } while (1);
I'd rather write this as:
struct user_namespace *user_ns = ns->user_ns;
while (user_ns) {
ns = user_ns->ima_ns;
ret = __process_measurement(ns, file, cred, secid, buf,
size, mask, func);
if (ret)
break;
user_ns = user_ns->parent;
}
because the hierarchy is only an implicit property inherited by ima
namespaces from the implementation of user namespaces. In other words,
we're only indirectly walking a hierarchy of ima namespaces because
we're walking a hierarchy of user namespaces. So the ima ns actually
just gives us the entrypoint into the userns hierarchy which the double
deref writing it with a while() makes obvious.
