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 <[email protected]>
---
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
Ping.
On 2022/11/18 11:28, ruanjinjie wrote:
> 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 <[email protected]>
> ---
> 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,
[Cc +vfio-ap, vfio-ccw]
On Fri, 18 Nov 2022 11:28:27 +0800
ruanjinjie <[email protected]> wrote:
> 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 <[email protected]>
> ---
> 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,
vfio-ap has a similar unwind as the sample drivers, but actually makes
an attempt to catch this ex:
...
ret = device_register(&matrix_dev->device);
if (ret)
goto matrix_reg_err;
ret = driver_register(&matrix_driver);
if (ret)
goto matrix_drv_err;
return 0;
matrix_drv_err:
device_unregister(&matrix_dev->device);
matrix_reg_err:
put_device(&matrix_dev->device);
...
So of the vfio drivers calling device_register(), vfio-ap is the only
one that does a put_device() if device_register() fails, but it also
seems sketchy to call both device_unregister() and put_device() in the
case that we exit via matrix_drv_err.
I wonder if all of these shouldn't adopt a flow like:
ret = device_register(&dev);
if (ret)
goto err1;
....
return 0;
err2:
device_del(&dev);
err1:
put_device(&dev);
Thanks,
Alex
> 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,
On 2022/12/1 7:06, Alex Williamson wrote:
> [Cc +vfio-ap, vfio-ccw]
>
> On Fri, 18 Nov 2022 11:28:27 +0800
> ruanjinjie <[email protected]> wrote:
>
>> 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 <[email protected]>
>> ---
>> 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,
>
>
> vfio-ap has a similar unwind as the sample drivers, but actually makes
> an attempt to catch this ex:
I think the reason is vfio-ap driver error path has common unwind to do
before device_register, otherwise it can return just after put_device or
device_unregister.
>
> ...
> ret = device_register(&matrix_dev->device);
> if (ret)
> goto matrix_reg_err;
>
> ret = driver_register(&matrix_driver);
> if (ret)
> goto matrix_drv_err;
>
> return 0;
>
> matrix_drv_err:
> device_unregister(&matrix_dev->device);
> matrix_reg_err:
> put_device(&matrix_dev->device);
> ...
>
> So of the vfio drivers calling device_register(), vfio-ap is the only
> one that does a put_device() if device_register() fails, but it also
> seems sketchy to call both device_unregister() and put_device() in the
> case that we exit via matrix_drv_err.
The patch do not change the original error path, just add missing
put_device out of the normal error path if device_register fails , so
there is no risk of calling both device_unregister() and put_device().
>
> I wonder if all of these shouldn't adopt a flow like:
>
> ret = device_register(&dev);
> if (ret)
> goto err1;
>
> ....
>
> return 0;
>
> err2:
> device_del(&dev);
> err1:
> put_device(&dev);
>
> Thanks,
>
> Alex
>
>> 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,
>
> From: Alex Williamson <[email protected]>
> Sent: Thursday, December 1, 2022 7:06 AM
>
> [Cc +vfio-ap, vfio-ccw]
>
> On Fri, 18 Nov 2022 11:28:27 +0800
> ruanjinjie <[email protected]> wrote:
>
> > 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().
It's not just about the name. The problem of kboject not being
released is a bigger one.
put_device() is always required no matter device_register()
succeeds or not:
* NOTE: _Never_ directly free @dev after calling this function, even
* if it returned an error! Always use put_device() to give up the
* reference initialized in this function instead.
*/
int device_register(struct device *dev)
> > @@ -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,
>
>
> vfio-ap has a similar unwind as the sample drivers, but actually makes
> an attempt to catch this ex:
>
> ...
> ret = device_register(&matrix_dev->device);
> if (ret)
> goto matrix_reg_err;
>
> ret = driver_register(&matrix_driver);
> if (ret)
> goto matrix_drv_err;
>
> return 0;
>
> matrix_drv_err:
> device_unregister(&matrix_dev->device);
> matrix_reg_err:
> put_device(&matrix_dev->device);
> ...
>
> So of the vfio drivers calling device_register(), vfio-ap is the only
> one that does a put_device() if device_register() fails, but it also
> seems sketchy to call both device_unregister() and put_device() in the
> case that we exit via matrix_drv_err.
>
> I wonder if all of these shouldn't adopt a flow like:
>
> ret = device_register(&dev);
> if (ret)
> goto err1;
>
> ....
>
> return 0;
>
> err2:
> device_del(&dev);
> err1:
> put_device(&dev);
>
It's kind of a mixed model.
With above unwind it's clearer to use device_initialize() and device_add() instead.
Otherwise what this patch does looks better IMHO:
ret = device_register(&dev);
if (ret) {
put_device(&dev);
goto err1;
}
...
return 0;
err2:
device_unregister(&dev);
err1:
earlier_unwind();
On Thu, 1 Dec 2022 02:00:57 +0000
"Tian, Kevin" <[email protected]> wrote:
> > From: Alex Williamson <[email protected]>
> > Sent: Thursday, December 1, 2022 7:06 AM
> >
> > [Cc +vfio-ap, vfio-ccw]
> >
> > On Fri, 18 Nov 2022 11:28:27 +0800
> > ruanjinjie <[email protected]> wrote:
> >
> > > 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().
>
> It's not just about the name. The problem of kboject not being
> released is a bigger one.
>
> put_device() is always required no matter device_register()
> succeeds or not:
>
> * NOTE: _Never_ directly free @dev after calling this function, even
> * if it returned an error! Always use put_device() to give up the
> * reference initialized in this function instead.
> */
> int device_register(struct device *dev)
>
> > > @@ -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,
> >
> >
> > vfio-ap has a similar unwind as the sample drivers, but actually makes
> > an attempt to catch this ex:
> >
> > ...
> > ret = device_register(&matrix_dev->device);
> > if (ret)
> > goto matrix_reg_err;
> >
> > ret = driver_register(&matrix_driver);
> > if (ret)
> > goto matrix_drv_err;
> >
> > return 0;
> >
> > matrix_drv_err:
> > device_unregister(&matrix_dev->device);
> > matrix_reg_err:
> > put_device(&matrix_dev->device);
> > ...
> >
> > So of the vfio drivers calling device_register(), vfio-ap is the only
> > one that does a put_device() if device_register() fails, but it also
> > seems sketchy to call both device_unregister() and put_device() in the
> > case that we exit via matrix_drv_err.
> >
> > I wonder if all of these shouldn't adopt a flow like:
> >
> > ret = device_register(&dev);
> > if (ret)
> > goto err1;
> >
> > ....
> >
> > return 0;
> >
> > err2:
> > device_del(&dev);
> > err1:
> > put_device(&dev);
> >
>
> It's kind of a mixed model.
>
> With above unwind it's clearer to use device_initialize() and device_add() instead.
That would go against the comment for device_register() recommending
that device_initialize() and device_add() should only be called
separately if we have a clearly defined need. I can only imagine a
patch bot would quickly come along to rectify the situation if we
simply open code device_register() for aesthetics. I don't see that
splitting device_unregister() for the purpose of having a common unwind
path necessitates any changes relative to device_register().
> Otherwise what this patch does looks better IMHO:
>
> ret = device_register(&dev);
> if (ret) {
> put_device(&dev);
> goto err1;
> }
>
> ...
>
> return 0;
>
> err2:
> device_unregister(&dev);
> err1:
> earlier_unwind();
>
This is essentially what was originally proposed. It could also be
called a "mixed model", implementing part of the unwind in the error
branch before jumping to the common unwind. As demonstrated below,
every current vfio driver calling device_register() follows a similar
goto unwind stack as found in the sample drivers, which makes it
trivially easy to split the device_unregister() call and add a goto
target in between.
Either way, they're equivalent and I'll take whichever version
addresses all the vfio related use cases and gets acks from their
maintainers. Thanks,
Alex
diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
index c2a65808605a..54aba7cceb33 100644
--- a/drivers/s390/cio/vfio_ccw_drv.c
+++ b/drivers/s390/cio/vfio_ccw_drv.c
@@ -199,8 +199,9 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
return 0;
out_unreg:
- device_unregister(&parent->dev);
+ device_del(&parent->dev);
out_free:
+ put_device(&parent->dev);
dev_set_drvdata(&sch->dev, NULL);
return ret;
}
diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
index f43cfeabd2cc..997b524bdd2b 100644
--- a/drivers/s390/crypto/vfio_ap_drv.c
+++ b/drivers/s390/crypto/vfio_ap_drv.c
@@ -122,7 +122,7 @@ static int vfio_ap_matrix_dev_create(void)
return 0;
matrix_drv_err:
- device_unregister(&matrix_dev->device);
+ device_del(&matrix_dev->device);
matrix_reg_err:
put_device(&matrix_dev->device);
matrix_alloc_err:
diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
index 8b5a3a778a25..e54eb752e1ba 100644
--- a/samples/vfio-mdev/mbochs.c
+++ b/samples/vfio-mdev/mbochs.c
@@ -1430,7 +1430,7 @@ static int __init mbochs_dev_init(void)
ret = device_register(&mbochs_dev);
if (ret)
- goto err_class;
+ goto err_put;
ret = mdev_register_parent(&mbochs_parent, &mbochs_dev, &mbochs_driver,
mbochs_mdev_types,
@@ -1441,8 +1441,9 @@ static int __init mbochs_dev_init(void)
return 0;
err_device:
- device_unregister(&mbochs_dev);
-err_class:
+ device_del(&mbochs_dev);
+err_put:
+ put_device(&mbochs_dev);
class_destroy(mbochs_class);
err_driver:
mdev_unregister_driver(&mbochs_driver);
diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
index 721fb06c6413..e8400fdab71d 100644
--- a/samples/vfio-mdev/mdpy.c
+++ b/samples/vfio-mdev/mdpy.c
@@ -717,7 +717,7 @@ static int __init mdpy_dev_init(void)
ret = device_register(&mdpy_dev);
if (ret)
- goto err_class;
+ goto err_put;
ret = mdev_register_parent(&mdpy_parent, &mdpy_dev, &mdpy_driver,
mdpy_mdev_types,
@@ -728,8 +728,9 @@ static int __init mdpy_dev_init(void)
return 0;
err_device:
- device_unregister(&mdpy_dev);
-err_class:
+ device_del(&mdpy_dev);
+err_put:
+ put_device(&mdpy_dev);
class_destroy(mdpy_class);
err_driver:
mdev_unregister_driver(&mdpy_driver);
diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
index 3c2a421b9b69..e887de672c52 100644
--- a/samples/vfio-mdev/mtty.c
+++ b/samples/vfio-mdev/mtty.c
@@ -1330,7 +1330,7 @@ static int __init mtty_dev_init(void)
ret = device_register(&mtty_dev.dev);
if (ret)
- goto err_class;
+ goto err_put;
ret = mdev_register_parent(&mtty_dev.parent, &mtty_dev.dev,
&mtty_driver, mtty_mdev_types,
@@ -1340,8 +1340,9 @@ static int __init mtty_dev_init(void)
return 0;
err_device:
- device_unregister(&mtty_dev.dev);
-err_class:
+ device_del(&mtty_dev.dev);
+err_put:
+ put_device(&mtty_dev.dev);
class_destroy(mtty_dev.vd_class);
err_driver:
mdev_unregister_driver(&mtty_driver);
> From: Alex Williamson <[email protected]>
> Sent: Friday, December 2, 2022 5:10 AM
>
> > Otherwise what this patch does looks better IMHO:
> >
> > ret = device_register(&dev);
> > if (ret) {
> > put_device(&dev);
> > goto err1;
> > }
> >
> > ...
> >
> > return 0;
> >
> > err2:
> > device_unregister(&dev);
> > err1:
> > earlier_unwind();
> >
>
> This is essentially what was originally proposed. It could also be
> called a "mixed model", implementing part of the unwind in the error
> branch before jumping to the common unwind. As demonstrated below,
> every current vfio driver calling device_register() follows a similar
> goto unwind stack as found in the sample drivers, which makes it
> trivially easy to split the device_unregister() call and add a goto
> target in between.
OK. Actually looking into other users of device_register() I can
see both schemes are used, so...
>
> Either way, they're equivalent and I'll take whichever version
> addresses all the vfio related use cases and gets acks from their
> maintainers. Thanks,
... agree either way is fine. Since your version fixes all vfio cases,
feel free to include:
Reviewed-by: Kevin Tian <[email protected]>
>
> Alex
>
> diff --git a/drivers/s390/cio/vfio_ccw_drv.c
> b/drivers/s390/cio/vfio_ccw_drv.c
> index c2a65808605a..54aba7cceb33 100644
> --- a/drivers/s390/cio/vfio_ccw_drv.c
> +++ b/drivers/s390/cio/vfio_ccw_drv.c
> @@ -199,8 +199,9 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
> return 0;
>
> out_unreg:
> - device_unregister(&parent->dev);
> + device_del(&parent->dev);
> out_free:
> + put_device(&parent->dev);
> dev_set_drvdata(&sch->dev, NULL);
> return ret;
> }
> diff --git a/drivers/s390/crypto/vfio_ap_drv.c
> b/drivers/s390/crypto/vfio_ap_drv.c
> index f43cfeabd2cc..997b524bdd2b 100644
> --- a/drivers/s390/crypto/vfio_ap_drv.c
> +++ b/drivers/s390/crypto/vfio_ap_drv.c
> @@ -122,7 +122,7 @@ static int vfio_ap_matrix_dev_create(void)
> return 0;
>
> matrix_drv_err:
> - device_unregister(&matrix_dev->device);
> + device_del(&matrix_dev->device);
> matrix_reg_err:
> put_device(&matrix_dev->device);
> matrix_alloc_err:
> diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
> index 8b5a3a778a25..e54eb752e1ba 100644
> --- a/samples/vfio-mdev/mbochs.c
> +++ b/samples/vfio-mdev/mbochs.c
> @@ -1430,7 +1430,7 @@ static int __init mbochs_dev_init(void)
>
> ret = device_register(&mbochs_dev);
> if (ret)
> - goto err_class;
> + goto err_put;
>
> ret = mdev_register_parent(&mbochs_parent, &mbochs_dev,
> &mbochs_driver,
> mbochs_mdev_types,
> @@ -1441,8 +1441,9 @@ static int __init mbochs_dev_init(void)
> return 0;
>
> err_device:
> - device_unregister(&mbochs_dev);
> -err_class:
> + device_del(&mbochs_dev);
> +err_put:
> + put_device(&mbochs_dev);
> class_destroy(mbochs_class);
> err_driver:
> mdev_unregister_driver(&mbochs_driver);
> diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
> index 721fb06c6413..e8400fdab71d 100644
> --- a/samples/vfio-mdev/mdpy.c
> +++ b/samples/vfio-mdev/mdpy.c
> @@ -717,7 +717,7 @@ static int __init mdpy_dev_init(void)
>
> ret = device_register(&mdpy_dev);
> if (ret)
> - goto err_class;
> + goto err_put;
>
> ret = mdev_register_parent(&mdpy_parent, &mdpy_dev,
> &mdpy_driver,
> mdpy_mdev_types,
> @@ -728,8 +728,9 @@ static int __init mdpy_dev_init(void)
> return 0;
>
> err_device:
> - device_unregister(&mdpy_dev);
> -err_class:
> + device_del(&mdpy_dev);
> +err_put:
> + put_device(&mdpy_dev);
> class_destroy(mdpy_class);
> err_driver:
> mdev_unregister_driver(&mdpy_driver);
> diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
> index 3c2a421b9b69..e887de672c52 100644
> --- a/samples/vfio-mdev/mtty.c
> +++ b/samples/vfio-mdev/mtty.c
> @@ -1330,7 +1330,7 @@ static int __init mtty_dev_init(void)
>
> ret = device_register(&mtty_dev.dev);
> if (ret)
> - goto err_class;
> + goto err_put;
>
> ret = mdev_register_parent(&mtty_dev.parent, &mtty_dev.dev,
> &mtty_driver, mtty_mdev_types,
> @@ -1340,8 +1340,9 @@ static int __init mtty_dev_init(void)
> return 0;
>
> err_device:
> - device_unregister(&mtty_dev.dev);
> -err_class:
> + device_del(&mtty_dev.dev);
> +err_put:
> + put_device(&mtty_dev.dev);
> class_destroy(mtty_dev.vd_class);
> err_driver:
> mdev_unregister_driver(&mtty_driver);
On Fri, 2022-12-02 at 05:28 +0000, Tian, Kevin wrote:
> > From: Alex Williamson <[email protected]>
> > Sent: Friday, December 2, 2022 5:10 AM
> >
> > > Otherwise what this patch does looks better IMHO:
> > >
> > > ret = device_register(&dev);
> > > if (ret) {
> > > put_device(&dev);
> > > goto err1;
> > > }
> > >
> > > ...
> > >
> > > return 0;
> > >
> > > err2:
> > > device_unregister(&dev);
> > > err1:
> > > earlier_unwind();
> > >
> >
> > This is essentially what was originally proposed. It could also be
> > called a "mixed model", implementing part of the unwind in the
> > error
> > branch before jumping to the common unwind. As demonstrated below,
> > every current vfio driver calling device_register() follows a
> > similar
> > goto unwind stack as found in the sample drivers, which makes it
> > trivially easy to split the device_unregister() call and add a goto
> > target in between.
>
> OK. Actually looking into other users of device_register() I can
> see both schemes are used, so...
>
> >
> > Either way, they're equivalent and I'll take whichever version
> > addresses all the vfio related use cases and gets acks from their
> > maintainers. Thanks,
>
> ... agree either way is fine. Since your version fixes all vfio
> cases,
> feel free to include:
>
> Reviewed-by: Kevin Tian <[email protected]>
>
> >
> > Alex
> >
> > diff --git a/drivers/s390/cio/vfio_ccw_drv.c
> > b/drivers/s390/cio/vfio_ccw_drv.c
> > index c2a65808605a..54aba7cceb33 100644
> > --- a/drivers/s390/cio/vfio_ccw_drv.c
> > +++ b/drivers/s390/cio/vfio_ccw_drv.c
> > @@ -199,8 +199,9 @@ static int vfio_ccw_sch_probe(struct subchannel
> > *sch)
> > return 0;
> >
> > out_unreg:
> > - device_unregister(&parent->dev);
> > + device_del(&parent->dev);
> > out_free:
> > + put_device(&parent->dev);
> > dev_set_drvdata(&sch->dev, NULL);
> > return ret;
> > }
Ugh, sorry. I had this partially right at one point but missed this
scenario when fixing the parts I had wrong.
This is fine by me, thanks for the fixup:
Reviewed-by: Eric Farman <[email protected]>
> > diff --git a/drivers/s390/crypto/vfio_ap_drv.c
> > b/drivers/s390/crypto/vfio_ap_drv.c
> > index f43cfeabd2cc..997b524bdd2b 100644
> > --- a/drivers/s390/crypto/vfio_ap_drv.c
> > +++ b/drivers/s390/crypto/vfio_ap_drv.c
> > @@ -122,7 +122,7 @@ static int vfio_ap_matrix_dev_create(void)
> > return 0;
> >
> > matrix_drv_err:
> > - device_unregister(&matrix_dev->device);
> > + device_del(&matrix_dev->device);
> > matrix_reg_err:
> > put_device(&matrix_dev->device);
> > matrix_alloc_err:
> > diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-
> > mdev/mbochs.c
> > index 8b5a3a778a25..e54eb752e1ba 100644
> > --- a/samples/vfio-mdev/mbochs.c
> > +++ b/samples/vfio-mdev/mbochs.c
> > @@ -1430,7 +1430,7 @@ static int __init mbochs_dev_init(void)
> >
> > ret = device_register(&mbochs_dev);
> > if (ret)
> > - goto err_class;
> > + goto err_put;
> >
> > ret = mdev_register_parent(&mbochs_parent, &mbochs_dev,
> > &mbochs_driver,
> > mbochs_mdev_types,
> > @@ -1441,8 +1441,9 @@ static int __init mbochs_dev_init(void)
> > return 0;
> >
> > err_device:
> > - device_unregister(&mbochs_dev);
> > -err_class:
> > + device_del(&mbochs_dev);
> > +err_put:
> > + put_device(&mbochs_dev);
> > class_destroy(mbochs_class);
> > err_driver:
> > mdev_unregister_driver(&mbochs_driver);
> > diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
> > index 721fb06c6413..e8400fdab71d 100644
> > --- a/samples/vfio-mdev/mdpy.c
> > +++ b/samples/vfio-mdev/mdpy.c
> > @@ -717,7 +717,7 @@ static int __init mdpy_dev_init(void)
> >
> > ret = device_register(&mdpy_dev);
> > if (ret)
> > - goto err_class;
> > + goto err_put;
> >
> > ret = mdev_register_parent(&mdpy_parent, &mdpy_dev,
> > &mdpy_driver,
> > mdpy_mdev_types,
> > @@ -728,8 +728,9 @@ static int __init mdpy_dev_init(void)
> > return 0;
> >
> > err_device:
> > - device_unregister(&mdpy_dev);
> > -err_class:
> > + device_del(&mdpy_dev);
> > +err_put:
> > + put_device(&mdpy_dev);
> > class_destroy(mdpy_class);
> > err_driver:
> > mdev_unregister_driver(&mdpy_driver);
> > diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
> > index 3c2a421b9b69..e887de672c52 100644
> > --- a/samples/vfio-mdev/mtty.c
> > +++ b/samples/vfio-mdev/mtty.c
> > @@ -1330,7 +1330,7 @@ static int __init mtty_dev_init(void)
> >
> > ret = device_register(&mtty_dev.dev);
> > if (ret)
> > - goto err_class;
> > + goto err_put;
> >
> > ret = mdev_register_parent(&mtty_dev.parent, &mtty_dev.dev,
> > &mtty_driver, mtty_mdev_types,
> > @@ -1340,8 +1340,9 @@ static int __init mtty_dev_init(void)
> > return 0;
> >
> > err_device:
> > - device_unregister(&mtty_dev.dev);
> > -err_class:
> > + device_del(&mtty_dev.dev);
> > +err_put:
> > + put_device(&mtty_dev.dev);
> > class_destroy(mtty_dev.vd_class);
> > err_driver:
> > mdev_unregister_driver(&mtty_driver);
>