[PATCH] vfio/mdev: fix possible memory leak in module init funcs

[ruanjinjie]

Inject fault while probing module, if device_register() fails,
but the refcount of kobject is not decreased to 0, the name
allocated in dev_set_name() is leaked. Fix this by calling
put_device(), so that name can be freed in callback function
kobject_cleanup().

unreferenced object 0xffff88807d687008 (size 8):
  comm "modprobe", pid 8280, jiffies 4294807686 (age 12.378s)
  hex dump (first 8 bytes):
    6d 64 70 79 00 6b 6b a5                          mdpy.kk.
  backtrace:
    [<ffffffff8174f19e>] __kmalloc_node_track_caller+0x4e/0x150
    [<ffffffff81731d53>] kstrdup+0x33/0x60
    [<ffffffff83aa1421>] kobject_set_name_vargs+0x41/0x110
    [<ffffffff82d91abb>] dev_set_name+0xab/0xe0
    [<ffffffffa0260105>] 0xffffffffa0260105
    [<ffffffff81001c27>] do_one_initcall+0x87/0x2e0
    [<ffffffff813739cb>] do_init_module+0x1ab/0x640
    [<ffffffff81379d20>] load_module+0x5d00/0x77f0
    [<ffffffff8137bc40>] __do_sys_finit_module+0x110/0x1b0
    [<ffffffff83c944a5>] do_syscall_64+0x35/0x80
    [<ffffffff83e0006a>] entry_SYSCALL_64_after_hwframe+0x46/0xb0

unreferenced object 0xffff888101ccbcf8 (size 8):
  comm "modprobe", pid 15662, jiffies 4295164481 (age 13.282s)
  hex dump (first 8 bytes):
    6d 74 74 79 00 6b 6b a5                          mtty.kk.
  backtrace:
    [<ffffffff8174f19e>] __kmalloc_node_track_caller+0x4e/0x150
    [<ffffffff81731d53>] kstrdup+0x33/0x60
    [<ffffffff83aa1421>] kobject_set_name_vargs+0x41/0x110
    [<ffffffff82d91abb>] dev_set_name+0xab/0xe0
    [<ffffffffa0248134>] 0xffffffffa0248134
    [<ffffffff81001c27>] do_one_initcall+0x87/0x2e0
    [<ffffffff813739cb>] do_init_module+0x1ab/0x640
    [<ffffffff81379d20>] load_module+0x5d00/0x77f0
    [<ffffffff8137bc40>] __do_sys_finit_module+0x110/0x1b0
    [<ffffffff83c944a5>] do_syscall_64+0x35/0x80
    [<ffffffff83e0006a>] entry_SYSCALL_64_after_hwframe+0x46/0xb0

unreferenced object 0xffff88810177c6c8 (size 8):
  comm "modprobe", pid 23657, jiffies 4295314656 (age 13.227s)
  hex dump (first 8 bytes):
    6d 62 6f 63 68 73 00 a5                          mbochs..
  backtrace:
    [<ffffffff8174f19e>] __kmalloc_node_track_caller+0x4e/0x150
    [<ffffffff81731d53>] kstrdup+0x33/0x60
    [<ffffffff83aa1421>] kobject_set_name_vargs+0x41/0x110
    [<ffffffff82d91abb>] dev_set_name+0xab/0xe0
    [<ffffffffa0248124>] 0xffffffffa0248124
    [<ffffffff81001c27>] do_one_initcall+0x87/0x2e0
    [<ffffffff813739cb>] do_init_module+0x1ab/0x640
    [<ffffffff81379d20>] load_module+0x5d00/0x77f0
    [<ffffffff8137bc40>] __do_sys_finit_module+0x110/0x1b0
    [<ffffffff83c944a5>] do_syscall_64+0x35/0x80
    [<ffffffff83e0006a>] entry_SYSCALL_64_after_hwframe+0x46/0xb0

Fixes: d61fc96f47fd ("sample: vfio mdev display - host device")
Fixes: 9d1a546c53b4 ("docs: Sample driver to demonstrate how to use Mediated device framework.")
Fixes: a5e6e6505f38 ("sample: vfio bochs vbe display (host device for bochs-drm)")
Signed-off-by: ruanjinjie <ruanjinjie@xxxxxxxxxx>
---
 samples/vfio-mdev/mbochs.c | 4 +++-
 samples/vfio-mdev/mdpy.c   | 4 +++-
 samples/vfio-mdev/mtty.c   | 4 +++-
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
index 117a8d799f71..1c47672be815 100644
--- a/samples/vfio-mdev/mbochs.c
+++ b/samples/vfio-mdev/mbochs.c
@@ -1430,8 +1430,10 @@ static int __init mbochs_dev_init(void)
 	dev_set_name(&mbochs_dev, "%s", MBOCHS_NAME);
 
 	ret = device_register(&mbochs_dev);
-	if (ret)
+	if (ret) {
+		put_device(&mbochs_dev);
 		goto err_class;
+	}
 
 	ret = mdev_register_parent(&mbochs_parent, &mbochs_dev, &mbochs_driver,
 				   mbochs_mdev_types,
diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
index 946e8cfde6fd..bfb93eaf535b 100644
--- a/samples/vfio-mdev/mdpy.c
+++ b/samples/vfio-mdev/mdpy.c
@@ -717,8 +717,10 @@ static int __init mdpy_dev_init(void)
 	dev_set_name(&mdpy_dev, "%s", MDPY_NAME);
 
 	ret = device_register(&mdpy_dev);
-	if (ret)
+	if (ret) {
+		put_device(&mdpy_dev);
 		goto err_class;
+	}
 
 	ret = mdev_register_parent(&mdpy_parent, &mdpy_dev, &mdpy_driver,
 				   mdpy_mdev_types,
diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
index e72085fc1376..dddb0619846c 100644
--- a/samples/vfio-mdev/mtty.c
+++ b/samples/vfio-mdev/mtty.c
@@ -1330,8 +1330,10 @@ static int __init mtty_dev_init(void)
 	dev_set_name(&mtty_dev.dev, "%s", MTTY_NAME);
 
 	ret = device_register(&mtty_dev.dev);
-	if (ret)
+	if (ret) {
+		put_device(&mtty_dev.dev);
 		goto err_class;
+	}
 
 	ret = mdev_register_parent(&mtty_dev.parent, &mtty_dev.dev,
 				   &mtty_driver, mtty_mdev_types,
-- 
2.25.1