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SubjectRe: [PATCH] Add default binder devices through binderfs when configured
On Thu, Aug 01, 2019 at 03:35:56PM -0700, Hridya Valsaraju wrote:
> If 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>
> ---
> drivers/android/binder.c | 3 ++-
> drivers/android/binderfs.c | 46 ++++++++++++++++++++++++++++++++++----
> 2 files changed, 44 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 466b6a7f8ab7..65a99ac26711 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -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/binderfs.c b/drivers/android/binderfs.c
> index e773f45d19d9..9f5ed50ffd70 100644
> --- a/drivers/android/binderfs.c
> +++ b/drivers/android/binderfs.c
> @@ -48,6 +48,10 @@ static dev_t binderfs_dev;
> static DEFINE_MUTEX(binderfs_minors_mutex);
> static DEFINE_IDA(binderfs_minors);
>
> +static char *binder_devices_param = CONFIG_ANDROID_BINDER_DEVICES;
> +module_param_named(devices, binder_devices_param, charp, 0444);
> +MODULE_PARM_DESC(devices, "Binder devices to be created by default");
> +

Why are you creating a module parameter? That was not in your changelog
:(



> /**
> * binderfs_mount_opts - mount options for binderfs
> * @max: maximum number of allocatable binderfs binder devices
> @@ -135,7 +139,6 @@ static int binderfs_binder_device_create(struct inode *ref_inode,
> #else
> bool use_reserve = true;
> #endif
> -
> /* Reserve new minor number for the new device. */
> mutex_lock(&binderfs_minors_mutex);
> if (++info->device_count <= info->mount_opts.max)
> @@ -186,8 +189,7 @@ 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 +469,9 @@ 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 +526,28 @@ 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, ",")) {
> + /*
> + * init_binderfs() has already checked that the length of
> + * device_name_entry->name is not greater than device_info.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,
> @@ -553,6 +579,18 @@ static struct file_system_type binder_fs_type = {
> int __init init_binderfs(void)
> {
> int ret;
> + const char *name;
> + size_t len;
> +
> + /* Verify that the default binderfs device names are valid. */
> + name = binder_devices_param;
> + for (len = strcspn(name, ","); len > 0; len = strcspn(name, ",")) {
> + if (len > BINDERFS_MAX_NAME)
> + return -E2BIG;
> + name += len;
> + if (*name == ',')
> + name++;
> + }

This verification should be a separate patch, right?

But the real issue here is I have no idea _why_ you are wanting this
patch. The changelog text says _what_ you are doing only, which isn't
ok.

Please provide more information as to why this is needed, what problem
it is solving, and break this up into a patch series and resend.

thanks,

greg k-h

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