linux-kernel - Re: [syzbot] [ntfs3?] KASAN: slab-use-after-free Read in chrdev

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Message-Id: <20240614124811.689-1-hdanton@sina.com>
Date: Fri, 14 Jun 2024 20:48:11 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+5d34cc6474499a5ff516@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [ntfs3?] KASAN: slab-use-after-free Read in chrdev_open

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  83a7eefedc9b

--- x/fs/open.c
+++ y/fs/open.c
@@ -952,7 +952,18 @@ static int do_dentry_open(struct file *f
 	if (!open)
 		open = f->f_op->open;
 	if (open) {
+		struct super_block *sb = inode->i_sb;
+
+		error = -EINVAL;
+		for (;;) {
+			int a = atomic_read(&sb->s_active);
+			if (a < 2)
+				goto cleanup_all;
+			if (a == atomic_cmpxchg(&sb->s_active, a a+1))
+				break;
+		}
 		error = open(inode, f);
+		deactivate_super(sb);
 		if (error)
 			goto cleanup_all;
 	}
--