Re: [PATCH v3 1/2] binder: Add default binder devices through binderfs when configured

[Joel Fernandes <joel@joelfernandes.org>]

On Thu, Aug 08, 2019 at 03:27:25PM -0700, Hridya Valsaraju wrote:
> Currently, since each binderfs instance needs its own
> private binder devices, every time a binderfs instance is
> mounted, all the default binder devices need to be created
> via the BINDER_CTL_ADD IOCTL. This patch aims to
> add a solution to automatically create the default binder
> devices for each binderfs instance that gets mounted.
> To achieve this goal, when CONFIG_ANDROID_BINDERFS is set,
> the default binder devices specified by CONFIG_ANDROID_BINDER_DEVICES
> are created in each binderfs instance instead of global devices
> being created by the binder driver.
> 
> Co-developed-by: Christian Brauner <christian.brauner@ubuntu.com>
> Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
> Signed-off-by: Hridya Valsaraju <hridya@google.com>

Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>

thanks,

 - Joel

> ---
> 
> Changes in v2:
> - Updated commit message as per Greg Kroah-Hartman.
> - Removed new module parameter creation as per Greg
>   Kroah-Hartman/Christian Brauner.
> - Refactored device name length check into a new patch as per Greg Kroah-Hartman.
> 
> Changes in v3:
> -Removed unnecessary empty lines as per Dan Carpenter.
> 
>  drivers/android/binder.c          |  5 +++--
>  drivers/android/binder_internal.h |  2 ++
>  drivers/android/binderfs.c        | 23 ++++++++++++++++++++---
>  3 files changed, 25 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 466b6a7f8ab7..ca6b21a53321 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -123,7 +123,7 @@ static uint32_t binder_debug_mask = BINDER_DEBUG_USER_ERROR |
>  	BINDER_DEBUG_FAILED_TRANSACTION | BINDER_DEBUG_DEAD_TRANSACTION;
>  module_param_named(debug_mask, binder_debug_mask, uint, 0644);
>  
> -static char *binder_devices_param = CONFIG_ANDROID_BINDER_DEVICES;
> +char *binder_devices_param = CONFIG_ANDROID_BINDER_DEVICES;
>  module_param_named(devices, binder_devices_param, charp, 0444);
>  
>  static DECLARE_WAIT_QUEUE_HEAD(binder_user_error_wait);
> @@ -6279,7 +6279,8 @@ static int __init binder_init(void)
>  				    &transaction_log_fops);
>  	}
>  
> -	if (strcmp(binder_devices_param, "") != 0) {
> +	if (!IS_ENABLED(CONFIG_ANDROID_BINDERFS) &&
> +	    strcmp(binder_devices_param, "") != 0) {
>  		/*
>  		* Copy the module_parameter string, because we don't want to
>  		* tokenize it in-place.
> diff --git a/drivers/android/binder_internal.h b/drivers/android/binder_internal.h
> index 045b3e42d98b..fe8c745dc8e0 100644
> --- a/drivers/android/binder_internal.h
> +++ b/drivers/android/binder_internal.h
> @@ -37,6 +37,8 @@ struct binder_device {
>  
>  extern const struct file_operations binder_fops;
>  
> +extern char *binder_devices_param;
> +
>  #ifdef CONFIG_ANDROID_BINDERFS
>  extern bool is_binderfs_device(const struct inode *inode);
>  #else
> diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
> index e773f45d19d9..aee46dd1be91 100644
> --- a/drivers/android/binderfs.c
> +++ b/drivers/android/binderfs.c
> @@ -186,8 +186,7 @@ static int binderfs_binder_device_create(struct inode *ref_inode,
>  	req->major = MAJOR(binderfs_dev);
>  	req->minor = minor;
>  
> -	ret = copy_to_user(userp, req, sizeof(*req));
> -	if (ret) {
> +	if (userp && copy_to_user(userp, req, sizeof(*req))) {
>  		ret = -EFAULT;
>  		goto err;
>  	}
> @@ -467,6 +466,9 @@ static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
>  	int ret;
>  	struct binderfs_info *info;
>  	struct inode *inode = NULL;
> +	struct binderfs_device device_info = { 0 };
> +	const char *name;
> +	size_t len;
>  
>  	sb->s_blocksize = PAGE_SIZE;
>  	sb->s_blocksize_bits = PAGE_SHIFT;
> @@ -521,7 +523,22 @@ static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
>  	if (!sb->s_root)
>  		return -ENOMEM;
>  
> -	return binderfs_binder_ctl_create(sb);
> +	ret = binderfs_binder_ctl_create(sb);
> +	if (ret)
> +		return ret;
> +
> +	name = binder_devices_param;
> +	for (len = strcspn(name, ","); len > 0; len = strcspn(name, ",")) {
> +		strscpy(device_info.name, name, len + 1);
> +		ret = binderfs_binder_device_create(inode, NULL, &device_info);
> +		if (ret)
> +			return ret;
> +		name += len;
> +		if (*name == ',')
> +			name++;
> +	}
> +
> +	return 0;
>  }
>  
>  static struct dentry *binderfs_mount(struct file_system_type *fs_type,
> -- 
> 2.22.0.770.g0f2c4a37fd-goog
>