[PATCH v3 7/7] loopfs: only show devices in their correct instance

From: Christian Brauner <christian.brauner@ubuntu.com>
To: Jens Axboe <axboe@kernel.dk>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-kernel@vger.kernel.org, linux-block@vger.kernel.org,
	linux-api@vger.kernel.org
Cc: "Jonathan Corbet" <corbet@lwn.net>,
	"Serge Hallyn" <serge@hallyn.com>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	"Tejun Heo" <tj@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	"Christian Brauner" <christian.brauner@ubuntu.com>,
	"Saravana Kannan" <saravanak@google.com>,
	"Jan Kara" <jack@suse.cz>, "David Howells" <dhowells@redhat.com>,
	"Seth Forshee" <seth.forshee@canonical.com>,
	"David Rheinsberg" <david.rheinsberg@gmail.com>,
	"Tom Gundersen" <teg@jklm.no>,
	"Christian Kellner" <ckellner@redhat.com>,
	"Dmitry Vyukov" <dvyukov@google.com>,
	"Stéphane Graber" <stgraber@ubuntu.com>,
	linux-doc@vger.kernel.org, netdev@vger.kernel.org,
	"Steve Barber" <smbarber@google.com>,
	"Dylan Reid" <dgreid@google.com>,
	"Filipe Brandenburger" <filbranden@gmail.com>,
	"Kees Cook" <keescook@chromium.org>,
	"Benjamin Elder" <bentheelder@google.com>,
	"Akihiro Suda" <suda.kyoto@gmail.com>
Subject: [PATCH v3 7/7] loopfs: only show devices in their correct instance
Date: Fri, 24 Apr 2020 18:20:52 +0200	[thread overview]
Message-ID: <20200424162052.441452-8-christian.brauner@ubuntu.com> (raw)
In-Reply-To: <20200424162052.441452-1-christian.brauner@ubuntu.com>

Since loopfs devices belong to a loopfs instance they have no business
polluting the host's devtmpfs mount and should not propagate out of the
namespace they belong to.

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
/* v2 */
unchanged

/* v3 */
unchanged
---
 block/partitions/core.c       | 1 +
 drivers/base/devtmpfs.c       | 4 ++--
 drivers/block/loopfs/loopfs.c | 4 +++-
 include/linux/device.h        | 3 +++
 4 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/block/partitions/core.c b/block/partitions/core.c
index bc1ded1331b1..5761f5c38588 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -416,6 +416,7 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno,
 	pdev->class = &block_class;
 	pdev->type = &part_type;
 	pdev->parent = ddev;
+	pdev->no_devnode = ddev->no_devnode;
 
 	err = blk_alloc_devt(p, &devt);
 	if (err)
diff --git a/drivers/base/devtmpfs.c b/drivers/base/devtmpfs.c
index c9017e0584c0..77371ceb88fa 100644
--- a/drivers/base/devtmpfs.c
+++ b/drivers/base/devtmpfs.c
@@ -111,7 +111,7 @@ int devtmpfs_create_node(struct device *dev)
 	const char *tmp = NULL;
 	struct req req;
 
-	if (!thread)
+	if (!thread || dev->no_devnode)
 		return 0;
 
 	req.mode = 0;
@@ -138,7 +138,7 @@ int devtmpfs_delete_node(struct device *dev)
 	const char *tmp = NULL;
 	struct req req;
 
-	if (!thread)
+	if (!thread || dev->no_devnode)
 		return 0;
 
 	req.name = device_get_devnode(dev, NULL, NULL, NULL, &tmp);
diff --git a/drivers/block/loopfs/loopfs.c b/drivers/block/loopfs/loopfs.c
index 9fa60c1bcc05..1bcb0b44c910 100644
--- a/drivers/block/loopfs/loopfs.c
+++ b/drivers/block/loopfs/loopfs.c
@@ -76,8 +76,10 @@ bool loopfs_wants_remove(const struct loop_device *lo)
 
 void loopfs_init(struct gendisk *disk, struct inode *inode)
 {
-	if (loopfs_i_sb(inode))
+	if (loopfs_i_sb(inode)) {
 		disk->user_ns = loopfs_i_sb(inode)->s_user_ns;
+		disk_to_dev(disk)->no_devnode = true;
+	}
 }
 
 /**
diff --git a/include/linux/device.h b/include/linux/device.h
index ac8e37cd716a..c69ef1c5a0ef 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -523,6 +523,8 @@ struct dev_links_info {
  *		  sync_state() callback.
  * @dma_coherent: this particular device is dma coherent, even if the
  *		architecture supports non-coherent devices.
+ * @no_devnode: whether device nodes associated with this device are kept out
+ *		of devtmpfs (e.g. due to separate filesystem)
  *
  * At the lowest level, every device in a Linux system is represented by an
  * instance of struct device. The device structure contains the information
@@ -622,6 +624,7 @@ struct device {
     defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL)
 	bool			dma_coherent:1;
 #endif
+	bool			no_devnode:1;
 };
 
 static inline struct device *kobj_to_dev(struct kobject *kobj)
-- 
2.26.2

