[PATCH] rust_binderfs: fix minor number leak on binder-control creation failure

[Adhyansh Verma <adhyanshverma2010@gmail.com>]

In binderfs_binder_ctl_create(), a minor number is reserved using
ida_alloc_max(). If d_alloc_name() subsequently fails (e.g. under memory
pressure), the function jumps to the error path.

However, the cleanup path only calls kfree(device) and iput(inode).
Because inode->i_private has not yet been set to device, the eviction
handler binderfs_evict_inode() returns early without freeing the minor
number. Consequently, the reserved minor number is permanently leaked
from the global binderfs_minors IDA.

Fix this by introducing proper error unwind labels so that the allocated
minor number is released via ida_free() under binderfs_minors_mutex if
dentry allocation fails.

Fixes: eafedbc7c050 ("rust_binder: add Rust Binder driver")
Signed-off-by: Adhyansh Verma <adhyanshverma2010@gmail.com>
---
 drivers/android/binder/rust_binderfs.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/android/binder/rust_binderfs.c b/drivers/android/binder/rust_binderfs.c
index 5f020226720d..3f7ff0fdbdb9 100644
--- a/drivers/android/binder/rust_binderfs.c
+++ b/drivers/android/binder/rust_binderfs.c
@@ -400,7 +400,7 @@ static int binderfs_binder_ctl_create(struct super_block *sb)
 	ret = -ENOMEM;
 	inode = new_inode(sb);
 	if (!inode)
-		goto out;
+		goto out_device;
 
 	/* Reserve a new minor number for the new device. */
 	mutex_lock(&binderfs_minors_mutex);
@@ -411,7 +411,7 @@ static int binderfs_binder_ctl_create(struct super_block *sb)
 	mutex_unlock(&binderfs_minors_mutex);
 	if (minor < 0) {
 		ret = minor;
-		goto out;
+		goto out_inode;
 	}
 
 	inode->i_ino = SECOND_INODE;
@@ -427,7 +427,7 @@ static int binderfs_binder_ctl_create(struct super_block *sb)
 
 	dentry = d_alloc_name(root, "binder-control");
 	if (!dentry)
-		goto out;
+		goto out_minor;
 
 	inode->i_private = device;
 	info->control_dentry = dentry;
@@ -436,9 +436,14 @@ static int binderfs_binder_ctl_create(struct super_block *sb)
 
 	return 0;
 
-out:
-	kfree(device);
+out_minor:
+	mutex_lock(&binderfs_minors_mutex);
+	ida_free(&binderfs_minors, minor);
+	mutex_unlock(&binderfs_minors_mutex);
+out_inode:
 	iput(inode);
+out_device:
+	kfree(device);
 
 	return ret;
 }
-- 
2.56.0