Re: [PATCH] driver core: Fix possible memory leak in device_link_add()

[Saravana Kannan]

On Thu, Sep 30, 2021 at 1:52 AM Yang Yingliang <yangyingliang@xxxxxxxxxx> wrote:
>
> I got memory leak as follows:
>
> unreferenced object 0xffff88801f0b2200 (size 64):
>   comm "i2c-lis2hh12-21", pid 5455, jiffies 4294944606 (age 15.224s)
>   hex dump (first 32 bytes):
>     72 65 67 75 6c 61 74 6f 72 3a 72 65 67 75 6c 61  regulator:regula
>     74 6f 72 2e 30 2d 2d 69 32 63 3a 31 2d 30 30 31  tor.0--i2c:1-001
>   backtrace:
>     [<00000000bf5b0c3b>] __kmalloc_track_caller+0x19f/0x3a0
>     [<0000000050da42d9>] kvasprintf+0xb5/0x150
>     [<000000004bbbed13>] kvasprintf_const+0x60/0x190
>     [<00000000cdac7480>] kobject_set_name_vargs+0x56/0x150
>     [<00000000bf83f8e8>] dev_set_name+0xc0/0x100
>     [<00000000cc1cf7e3>] device_link_add+0x6b4/0x17c0
>     [<000000009db9faed>] _regulator_get+0x297/0x680
>     [<00000000845e7f2b>] _devm_regulator_get+0x5b/0xe0
>     [<000000003958ee25>] st_sensors_power_enable+0x71/0x1b0 [st_sensors]
>     [<000000005f450f52>] st_accel_i2c_probe+0xd9/0x150 [st_accel_i2c]
>     [<00000000b5f2ab33>] i2c_device_probe+0x4d8/0xbe0
>     [<0000000070fb977b>] really_probe+0x299/0xc30
>     [<0000000088e226ce>] __driver_probe_device+0x357/0x500
>     [<00000000c21dda32>] driver_probe_device+0x4e/0x140
>     [<000000004e650441>] __device_attach_driver+0x257/0x340
>     [<00000000cf1891b8>] bus_for_each_drv+0x166/0x1e0
>
> When device_register() returns an error, the name allocated in dev_set_name()
> will be leaked, the put_device() should be used instead of kfree() to give up
> the device reference, then the name will be freed in kobject_cleanup() and the
> references of consumer and supplier will be decreased in device_link_release_fn().
>
> Fixes: 287905e68dd2 ("driver core: Expose device link details in sysfs")
> Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
> Signed-off-by: Yang Yingliang <yangyingliang@xxxxxxxxxx>
> ---
>  drivers/base/core.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index e65dd803a453..4a123e58711f 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -809,9 +809,7 @@ struct device_link *device_link_add(struct device *consumer,
>                      dev_bus_name(supplier), dev_name(supplier),
>                      dev_bus_name(consumer), dev_name(consumer));
>         if (device_register(&link->link_dev)) {
> -               put_device(consumer);
> -               put_device(supplier);
> -               kfree(link);
> +               put_device(&link->link_dev);
>                 link = NULL;
>                 goto out;
>         }
> --
> 2.25.1
>

Thanks for the fix!

Reviewed-by: Saravana Kannan <saravanak@xxxxxxxxxx>

Btw, can you also let us know why the device_register() is failing? It
really shouldn't be failing.

-Saravana