[PATCH v3] binderfs: free minor on binder-control creation failure

[Chao Huang <958028483@qq.com>]

From: Chao Huang <huangchao@kylinos.cn>

Both binderfs_binder_ctl_create() implementations allocate a minor before
creating the binder-control dentry. If d_alloc_name() fails, the error path
frees the device and drops the inode, but leaves the minor allocated in
binderfs_minors. Repeated failures can therefore exhaust the global minor
IDA.

Release the minor from a dedicated error path after a successful allocation
in both implementations.

Signed-off-by: Chao Huang <huangchao@kylinos.cn>
---
Changes in v3:
- Use a dedicated out_with_minor error path instead of an -ENOSPC sentinel.

 drivers/android/binder/rust_binderfs.c | 7 ++++++-
 drivers/android/binderfs.c             | 7 ++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/android/binder/rust_binderfs.c b/drivers/android/binder/rust_binderfs.c
index ade1c4d92499..0763e3db54bd 100644
--- a/drivers/android/binder/rust_binderfs.c
+++ b/drivers/android/binder/rust_binderfs.c
@@ -421,7 +421,7 @@ static int binderfs_binder_ctl_create(struct super_block *sb)
 
 	dentry = d_alloc_name(root, "binder-control");
 	if (!dentry)
-		goto out;
+		goto out_with_minor;
 
 	inode->i_private = device;
 	info->control_dentry = dentry;
@@ -430,6 +430,11 @@ static int binderfs_binder_ctl_create(struct super_block *sb)
 
 	return 0;
 
+out_with_minor:
+	mutex_lock(&binderfs_minors_mutex);
+	ida_free(&binderfs_minors, minor);
+	mutex_unlock(&binderfs_minors_mutex);
+
 out:
 	kfree(device);
 	iput(inode);
diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
index 361d69f756f5..0e96146ecf69 100644
--- a/drivers/android/binderfs.c
+++ b/drivers/android/binderfs.c
@@ -431,7 +431,7 @@ static int binderfs_binder_ctl_create(struct super_block *sb)
 
 	dentry = d_alloc_name(root, "binder-control");
 	if (!dentry)
-		goto out;
+		goto out_with_minor;
 
 	inode->i_private = device;
 	info->control_dentry = dentry;
@@ -440,6 +440,11 @@ static int binderfs_binder_ctl_create(struct super_block *sb)
 
 	return 0;
 
+out_with_minor:
+	mutex_lock(&binderfs_minors_mutex);
+	ida_free(&binderfs_minors, minor);
+	mutex_unlock(&binderfs_minors_mutex);
+
 out:
 	kfree(device);
 	iput(inode);

base-commit: c21bb4193868a8de71fc4693fa741e195fdf5d86
-- 
2.25.1