From:   Dongliang Mu <mudongliangabcd@gmail.com>
To:     Bart Van Assche <bvanassche@acm.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        "Theodore Ts'o" <tytso@mit.edu>,
        Muchun Song <songmuchun@bytedance.com>
Cc:     Dongliang Mu <mudongliangabcd@gmail.com>,
        syzbot+57e3e98f7e3b80f64d56@syzkaller.appspotmail.com,
        Jens Axboe <axboe@kernel.dk>, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] fs: hfsplus: Fix UAF issue in hfsplus_put_super
Date:   Sun, 26 Feb 2023 20:49:47 +0800
Message-Id: <20230226124948.3175736-1-mudongliangabcd@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The current hfsplus_put_super first calls hfs_btree_close on
sbi->ext_tree, then invokes iput on sbi->hidden_dir, resulting in an
use-after-free issue in hfsplus_release_folio.

As shown in hfsplus_fill_super, the error handling code also calls iput
before hfs_btree_close.

To fix this error, we move all iput calls before hfsplus_btree_close.

Note that this patch is tested on Syzbot.

Reported-by: syzbot+57e3e98f7e3b80f64d56@syzkaller.appspotmail.com
Tested-by: Dongliang Mu <mudongliangabcd@gmail.com>
Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
---
 fs/hfsplus/super.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/hfsplus/super.c b/fs/hfsplus/super.c
index 122ed89ebf9f..1986b4f18a90 100644
--- a/fs/hfsplus/super.c
+++ b/fs/hfsplus/super.c
@@ -295,11 +295,11 @@ static void hfsplus_put_super(struct super_block *sb)
 		hfsplus_sync_fs(sb, 1);
 	}
 
+	iput(sbi->alloc_file);
+	iput(sbi->hidden_dir);
 	hfs_btree_close(sbi->attr_tree);
 	hfs_btree_close(sbi->cat_tree);
 	hfs_btree_close(sbi->ext_tree);
-	iput(sbi->alloc_file);
-	iput(sbi->hidden_dir);
 	kfree(sbi->s_vhdr_buf);
 	kfree(sbi->s_backup_vhdr_buf);
 	unload_nls(sbi->nls);
-- 
2.34.1