linux-kernel - [PATCH 2/2] fs: btrfs: Don't leak memory when failing add fsid

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Message-Id: <20190513033912.3436-3-tobin@kernel.org>
Date:   Mon, 13 May 2019 13:39:12 +1000
From:   "Tobin C. Harding" <tobin@...nel.org>
To:     Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>
Cc:     "Tobin C. Harding" <tobin@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] fs: btrfs: Don't leak memory when failing add fsid

A failed call to kobject_init_and_add() must be followed by a call to
kobject_put().  Currently in the error path when adding fs_devices we
are missing this call.  This could be fixed by calling
btrfs_sysfs_remove_fsid() if btrfs_sysfs_add_fsid() returns an error or
by adding a call to kobject_put() directly in btrfs_sysfs_add_fsid().
Here we choose the second option because it prevents the slightly
unusual error path handling requirements of kobject from leaking out
into btrfs functions.

Add a call to kobject_put() in the error path of kobject_add_and_init().
This causes the release method to be called if kobject_init_and_add()
fails.  open_tree() is the function that calls btrfs_sysfs_add_fsid()
and the error code in this function is already written with the
assumption that the release method is called during the error path of
open_tree() (as seen by the call to btrfs_sysfs_remove_fsid() under the
fail_fsdev_sysfs label).

Signed-off-by: Tobin C. Harding <tobin@...nel.org>
---
 fs/btrfs/sysfs.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 5a5930e3d32b..2f078b77fe14 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -825,7 +825,12 @@ int btrfs_sysfs_add_fsid(struct btrfs_fs_devices *fs_devs,
 	fs_devs->fsid_kobj.kset = btrfs_kset;
 	error = kobject_init_and_add(&fs_devs->fsid_kobj,
 				&btrfs_ktype, parent, "%pU", fs_devs->fsid);
-	return error;
+	if (error) {
+		kobject_put(&fs_devs->fsid_kobj);
+		return error;
+	}
+
+	return 0;
 }

 int btrfs_sysfs_add_mounted(struct btrfs_fs_info *fs_info)
-- 
2.21.0