[PATCH 5/6] kdbus: pin namespaces on HELLO
From: David Herrmann
Date: Thu Jul 02 2015 - 04:30:45 EST
Whenever we send messages to a target connection, all we know about the
target is the 'struct file' associated with the kdbus connection. Hence,
we cannot know which namespaces a receiving process will be in when it
calls KDBUS_CMD_RECV on the message. So far, we pinned all metadata we
wanna send and translate it on RECV-time, since we then know the exact
namespaces to translate into.
This has several drawbacks:
- Depending on the process calling RECV, the behavior is different (as
multiple processes might be in different namespaces but share the same
fd). This is unwanted behavior, as described by Eric here:
http://www.spinics.net/lists/netdev/msg329322.html
- We need to pin metadata with a message instead of translating it right
away.
- We cannot prep a message at SEND time as we don't know the size of the
translated metadata. Hence, we need to do all that at RECV time.
This patch changes the namespace behavior. Instead of using the namespaces
at RECV time, we now pin the namespaces at HELLO (i.e., open()). So
regardless who calls RECV on this file-descriptor, the same namespaces
will be used.
This gives us the advantage that we now always know the target namespaces
for a message. Hence, we can now properly prep a message at SEND time and
never have to carry any metadata pins around.
Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx>
---
ipc/kdbus/bus.c | 2 +-
ipc/kdbus/connection.c | 8 +++++++-
ipc/kdbus/connection.h | 6 ++++++
ipc/kdbus/metadata.c | 54 ++++++++++++++++++++++++++------------------------
ipc/kdbus/metadata.h | 1 +
ipc/kdbus/queue.c | 1 +
6 files changed, 44 insertions(+), 28 deletions(-)
diff --git a/ipc/kdbus/bus.c b/ipc/kdbus/bus.c
index 7d2c336..8fffc2f 100644
--- a/ipc/kdbus/bus.c
+++ b/ipc/kdbus/bus.c
@@ -507,7 +507,7 @@ int kdbus_cmd_bus_creator_info(struct kdbus_conn *conn, void __user *argp)
goto exit;
}
- ret = kdbus_meta_export(bus->creator_meta, NULL, attach_flags,
+ ret = kdbus_meta_export(bus->creator_meta, NULL, conn, attach_flags,
slice, hdr_size, &meta_size);
if (ret < 0)
goto exit;
diff --git a/ipc/kdbus/connection.c b/ipc/kdbus/connection.c
index e5e9c1e..bf9a8a6 100644
--- a/ipc/kdbus/connection.c
+++ b/ipc/kdbus/connection.c
@@ -130,6 +130,9 @@ static struct kdbus_conn *kdbus_conn_new(struct kdbus_ep *ep, bool privileged,
atomic_set(&conn->lost_count, 0);
INIT_DELAYED_WORK(&conn->work, kdbus_reply_list_scan_work);
conn->cred = get_current_cred();
+ conn->user_ns = get_user_ns(current_user_ns());
+ conn->pid_ns = get_pid_ns(task_active_pid_ns(current));
+ get_fs_root(current->fs, &conn->root_path);
init_waitqueue_head(&conn->wait);
kdbus_queue_init(&conn->queue);
conn->privileged = privileged;
@@ -271,6 +274,9 @@ static void __kdbus_conn_free(struct kref *kref)
kdbus_match_db_free(conn->match_db);
kdbus_pool_free(conn->pool);
kdbus_ep_unref(conn->ep);
+ path_put(&conn->root_path);
+ put_pid_ns(conn->pid_ns);
+ put_user_ns(conn->user_ns);
put_cred(conn->cred);
kfree(conn->description);
kfree(conn->quota);
@@ -1792,7 +1798,7 @@ int kdbus_cmd_conn_info(struct kdbus_conn *conn, void __user *argp)
goto exit;
}
- ret = kdbus_meta_export(owner_conn->meta, conn_meta, attach_flags,
+ ret = kdbus_meta_export(owner_conn->meta, conn_meta, conn, attach_flags,
slice, sizeof(info), &meta_size);
if (ret < 0)
goto exit;
diff --git a/ipc/kdbus/connection.h b/ipc/kdbus/connection.h
index d1ffe90..226f3ff 100644
--- a/ipc/kdbus/connection.h
+++ b/ipc/kdbus/connection.h
@@ -59,6 +59,9 @@ struct kdbus_kmsg;
* @pool: The user's buffer to receive messages
* @user: Owner of the connection
* @cred: The credentials of the connection at creation time
+ * @user_ns: User namespace at creation time
+ * @pid_ns: Pid namespace at creation time
+ * @root_path: Root path at creation time
* @name_count: Number of owned well-known names
* @request_count: Number of pending requests issued by this
* connection that are waiting for replies from
@@ -97,6 +100,9 @@ struct kdbus_conn {
struct kdbus_pool *pool;
struct kdbus_user *user;
const struct cred *cred;
+ struct user_namespace *user_ns;
+ struct pid_namespace *pid_ns;
+ struct path root_path;
atomic_t name_count;
atomic_t request_count;
atomic_t lost_count;
diff --git a/ipc/kdbus/metadata.c b/ipc/kdbus/metadata.c
index c36b9cc..79f0e8c 100644
--- a/ipc/kdbus/metadata.c
+++ b/ipc/kdbus/metadata.c
@@ -888,7 +888,8 @@ static int kdbus_meta_push_kvec(struct kvec *kvec,
}
static void kdbus_meta_export_caps(struct kdbus_meta_caps *out,
- struct kdbus_meta_proc *mp)
+ struct kdbus_meta_proc *mp,
+ struct user_namespace *user_ns)
{
struct user_namespace *iter;
const struct cred *cred = mp->cred;
@@ -896,18 +897,18 @@ static void kdbus_meta_export_caps(struct kdbus_meta_caps *out,
int i;
/*
- * This translates the effective capabilities of 'cred' into the current
- * user-namespace. If the current user-namespace is a child-namespace of
+ * This translates the effective capabilities of 'cred' into the given
+ * user-namespace. If the given user-namespace is a child-namespace of
* the user-namespace of 'cred', the mask can be copied verbatim. If
* not, the mask is cleared.
* There's one exception: If 'cred' is the owner of any user-namespace
- * in the path between the current user-namespace and the user-namespace
+ * in the path between the given user-namespace and the user-namespace
* of 'cred', then it has all effective capabilities set. This means,
* the user who created a user-namespace always has all effective
* capabilities in any child namespaces. Note that this is based on the
* uid of the namespace creator, not the task hierarchy.
*/
- for (iter = current_user_ns(); iter; iter = iter->parent) {
+ for (iter = user_ns; iter; iter = iter->parent) {
if (iter == cred->user_ns) {
parent = true;
break;
@@ -951,23 +952,22 @@ static void kdbus_meta_export_caps(struct kdbus_meta_caps *out,
}
/* This is equivalent to from_kuid_munged(), but maps INVALID_UID to itself */
-static uid_t kdbus_from_kuid_keep(kuid_t uid)
+static uid_t kdbus_from_kuid_keep(struct user_namespace *ns, kuid_t uid)
{
- return uid_valid(uid) ?
- from_kuid_munged(current_user_ns(), uid) : ((uid_t)-1);
+ return uid_valid(uid) ? from_kuid_munged(ns, uid) : ((uid_t)-1);
}
/* This is equivalent to from_kgid_munged(), but maps INVALID_GID to itself */
-static gid_t kdbus_from_kgid_keep(kgid_t gid)
+static gid_t kdbus_from_kgid_keep(struct user_namespace *ns, kgid_t gid)
{
- return gid_valid(gid) ?
- from_kgid_munged(current_user_ns(), gid) : ((gid_t)-1);
+ return gid_valid(gid) ? from_kgid_munged(ns, gid) : ((gid_t)-1);
}
/**
* kdbus_meta_export() - export information from metadata into a slice
* @mp: Process metadata, or NULL
* @mc: Connection metadata, or NULL
+ * @conn: Target connection to translate metadata into
* @mask: Mask of KDBUS_ATTACH_* flags to export
* @slice: The slice to export to
* @offset: The offset inside @slice to write to
@@ -983,18 +983,19 @@ static gid_t kdbus_from_kgid_keep(kgid_t gid)
* kdbus_meta_export_prepare(); depending on the namespaces in question, it
* might use up less than that.
*
- * All information will be translated using the current namespaces.
+ * All information will be translated using the namespaces of @conn.
*
* Return: 0 on success, negative error number otherwise.
*/
int kdbus_meta_export(struct kdbus_meta_proc *mp,
struct kdbus_meta_conn *mc,
+ struct kdbus_conn *conn,
u64 mask,
struct kdbus_pool_slice *slice,
off_t offset,
size_t *real_size)
{
- struct user_namespace *user_ns = current_user_ns();
+ struct user_namespace *user_ns = conn->user_ns;
struct kdbus_item_header item_hdr[13], *hdr;
char *exe_pathname = NULL;
struct kdbus_creds creds;
@@ -1016,23 +1017,23 @@ int kdbus_meta_export(struct kdbus_meta_proc *mp,
/* process metadata */
if (mp && (mask & KDBUS_ATTACH_CREDS)) {
- creds.uid = kdbus_from_kuid_keep(mp->uid);
- creds.euid = kdbus_from_kuid_keep(mp->euid);
- creds.suid = kdbus_from_kuid_keep(mp->suid);
- creds.fsuid = kdbus_from_kuid_keep(mp->fsuid);
- creds.gid = kdbus_from_kgid_keep(mp->gid);
- creds.egid = kdbus_from_kgid_keep(mp->egid);
- creds.sgid = kdbus_from_kgid_keep(mp->sgid);
- creds.fsgid = kdbus_from_kgid_keep(mp->fsgid);
+ creds.uid = kdbus_from_kuid_keep(user_ns, mp->uid);
+ creds.euid = kdbus_from_kuid_keep(user_ns, mp->euid);
+ creds.suid = kdbus_from_kuid_keep(user_ns, mp->suid);
+ creds.fsuid = kdbus_from_kuid_keep(user_ns, mp->fsuid);
+ creds.gid = kdbus_from_kgid_keep(user_ns, mp->gid);
+ creds.egid = kdbus_from_kgid_keep(user_ns, mp->egid);
+ creds.sgid = kdbus_from_kgid_keep(user_ns, mp->sgid);
+ creds.fsgid = kdbus_from_kgid_keep(user_ns, mp->fsgid);
cnt += kdbus_meta_push_kvec(kvec + cnt, hdr++, KDBUS_ITEM_CREDS,
&creds, sizeof(creds), &size);
}
if (mp && (mask & KDBUS_ATTACH_PIDS)) {
- pids.pid = pid_vnr(mp->tgid);
- pids.tid = pid_vnr(mp->pid);
- pids.ppid = pid_vnr(mp->ppid);
+ pids.pid = pid_nr_ns(mp->tgid, conn->pid_ns);
+ pids.tid = pid_nr_ns(mp->pid, conn->pid_ns);
+ pids.ppid = pid_nr_ns(mp->ppid, conn->pid_ns);
cnt += kdbus_meta_push_kvec(kvec + cnt, hdr++, KDBUS_ITEM_PIDS,
&pids, sizeof(pids), &size);
@@ -1078,7 +1079,8 @@ int kdbus_meta_export(struct kdbus_meta_proc *mp,
*/
get_fs_root(current->fs, &p);
- if (path_equal(&p, &mp->root_path)) {
+ if (path_equal(&p, &mp->root_path) &&
+ path_equal(&p, &conn->root_path)) {
exe_page = (void *)__get_free_page(GFP_TEMPORARY);
if (!exe_page) {
path_put(&p);
@@ -1116,7 +1118,7 @@ int kdbus_meta_export(struct kdbus_meta_proc *mp,
if (mp && (mask & KDBUS_ATTACH_CAPS)) {
struct kdbus_meta_caps caps = {};
- kdbus_meta_export_caps(&caps, mp);
+ kdbus_meta_export_caps(&caps, mp, user_ns);
cnt += kdbus_meta_push_kvec(kvec + cnt, hdr++,
KDBUS_ITEM_CAPS, &caps,
sizeof(caps), &size);
diff --git a/ipc/kdbus/metadata.h b/ipc/kdbus/metadata.h
index 79b6ac3..2dbbb3d 100644
--- a/ipc/kdbus/metadata.h
+++ b/ipc/kdbus/metadata.h
@@ -46,6 +46,7 @@ int kdbus_meta_export_prepare(struct kdbus_meta_proc *mp,
u64 *mask, size_t *sz);
int kdbus_meta_export(struct kdbus_meta_proc *mp,
struct kdbus_meta_conn *mc,
+ struct kdbus_conn *conn,
u64 mask,
struct kdbus_pool_slice *slice,
off_t offset, size_t *real_size);
diff --git a/ipc/kdbus/queue.c b/ipc/kdbus/queue.c
index 25bb3ad..6650b78 100644
--- a/ipc/kdbus/queue.c
+++ b/ipc/kdbus/queue.c
@@ -479,6 +479,7 @@ int kdbus_queue_entry_install(struct kdbus_queue_entry *entry,
ret = kdbus_meta_export(entry->proc_meta,
entry->conn_meta,
+ conn_dst,
entry->attach_flags,
entry->slice,
entry->meta_offset,
--
2.4.5
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