[PATCH 08/14] fsinfo: Allow the mount topology propogation flags to be retrieved [ver #18]

From: David Howells <dhowells@redhat.com>
To: torvalds@linux-foundation.org, viro@zeniv.linux.org.uk
Cc: dhowells@redhat.com, raven@themaw.net, mszeredi@redhat.com,
	christian@brauner.io, jannh@google.com, darrick.wong@oracle.com,
	kzak@redhat.com, jlayton@redhat.com, linux-api@vger.kernel.org,
	linux-fsdevel@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH 08/14] fsinfo: Allow the mount topology propogation flags to be retrieved [ver #18]
Date: Mon, 09 Mar 2020 14:02:01 +0000	[thread overview]
Message-ID: <158376252176.344135.11226418366508725745.stgit@warthog.procyon.org.uk> (raw)
In-Reply-To: <158376244589.344135.12925590041630631412.stgit@warthog.procyon.org.uk>

Allow the mount topology propogation flags to be retrieved as part of the
FSINFO_ATTR_MOUNT_INFO attributes.

Signed-off-by: David Howells <dhowells@redhat.com>
---

 fs/namespace.c              |    7 ++++++-
 include/uapi/linux/fsinfo.h |    2 +-
 include/uapi/linux/mount.h  |   10 +++++++++-
 samples/vfs/test-fsinfo.c   |    1 +
 4 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index a6cb8c6b004f..88aef45bcfa8 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4177,15 +4177,20 @@ int fsinfo_generic_mount_info(struct path *path, struct fsinfo_context *ctx)
 			p->parent_id = p->mnt_id;
 		rcu_read_unlock();
 	}
-	if (IS_MNT_SHARED(m))
+	if (IS_MNT_SHARED(m)) {
 		p->group_id = m->mnt_group_id;
+		p->propagation |= MOUNT_PROPAGATION_SHARED;
+	}
 	if (IS_MNT_SLAVE(m)) {
 		int master = m->mnt_master->mnt_group_id;
 		int dom = get_dominating_id(m, &root);
 		p->master_id = master;
 		if (dom && dom != master)
 			p->from_id = dom;
+		p->propagation |= MOUNT_PROPAGATION_SLAVE;
 	}
+	if (IS_MNT_UNBINDABLE(m))
+		p->propagation |= MOUNT_PROPAGATION_UNBINDABLE;
 	path_put(&root);
 
 	flags = READ_ONCE(m->mnt.mnt_flags);
diff --git a/include/uapi/linux/fsinfo.h b/include/uapi/linux/fsinfo.h
index 7a8b577f54b7..909d6104933b 100644
--- a/include/uapi/linux/fsinfo.h
+++ b/include/uapi/linux/fsinfo.h
@@ -103,7 +103,7 @@ struct fsinfo_mount_info {
 	__u32	master_id;		/* Slave master group ID */
 	__u32	from_id;		/* Slave propagated from ID */
 	__u32	attr;			/* MOUNT_ATTR_* flags */
-	__u32	__padding[1];
+	__u32	propagation;		/* MOUNT_PROPAGATION_* flags */
 };
 
 #define FSINFO_ATTR_MOUNT_INFO__STRUCT struct fsinfo_mount_info
diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
index 96a0240f23fe..39e50fe9d8d9 100644
--- a/include/uapi/linux/mount.h
+++ b/include/uapi/linux/mount.h
@@ -105,7 +105,7 @@ enum fsconfig_command {
 #define FSMOUNT_CLOEXEC		0x00000001
 
 /*
- * Mount attributes.
+ * Mount object attributes (these are separate to filesystem attributes).
  */
 #define MOUNT_ATTR_RDONLY	0x00000001 /* Mount read-only */
 #define MOUNT_ATTR_NOSUID	0x00000002 /* Ignore suid and sgid bits */
@@ -117,4 +117,12 @@ enum fsconfig_command {
 #define MOUNT_ATTR_STRICTATIME	0x00000020 /* - Always perform atime updates */
 #define MOUNT_ATTR_NODIRATIME	0x00000080 /* Do not update directory access times */
 
+/*
+ * Mount object propogation attributes.
+ */
+#define MOUNT_PROPAGATION_UNBINDABLE	0x00000001 /* Mount is unbindable */
+#define MOUNT_PROPAGATION_SLAVE		0x00000002 /* Mount is slave */
+#define MOUNT_PROPAGATION_PRIVATE	0x00000000 /* Mount is private (ie. not shared) */
+#define MOUNT_PROPAGATION_SHARED	0x00000004 /* Mount is shared */
+
 #endif /* _UAPI_LINUX_MOUNT_H */
diff --git a/samples/vfs/test-fsinfo.c b/samples/vfs/test-fsinfo.c
index 2f9fe3b24bca..bdc7ea952630 100644
--- a/samples/vfs/test-fsinfo.c
+++ b/samples/vfs/test-fsinfo.c
@@ -299,6 +299,7 @@ static void dump_fsinfo_generic_mount_info(void *reply, unsigned int size)
 	printf("\tparent  : %x\n", r->parent_id);
 	printf("\tgroup   : %x\n", r->group_id);
 	printf("\tattr    : %x\n", r->attr);
+	printf("\tpropag  : %x\n", r->propagation);
 }
 
 static void dump_fsinfo_generic_mount_child(void *reply, unsigned int size)


