Re: [syzbot] possible fix (linux-ntfs3)

[syzbot <syzbot+4d2aaeff9eb5a2cfec70@syzkaller.appspotmail.com>]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: possible fix (linux-ntfs3)
Author: almaz.alexandrovich@paragon-software.com

#syz test: https://github.com/Paragon-Software-Group/linux-ntfs3.git master

diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
index 128d49512f5d..4a2062e481a4 100644
--- a/fs/ntfs3/super.c
+++ b/fs/ntfs3/super.c
@@ -124,10 +124,15 @@ void ntfs_inode_printk(struct inode *inode, const char *fmt, ...)
 		struct dentry *de = d_find_alias(inode);
 
 		if (de) {
+			int len;
 			spin_lock(&de->d_lock);
-			snprintf(name, sizeof(s_name_buf), " \"%s\"",
-				 de->d_name.name);
+			len = snprintf(name, sizeof(s_name_buf), " \"%s\"",
+				       de->d_name.name);
 			spin_unlock(&de->d_lock);
+			if (len <= 0)
+				name[0] = 0;
+			else if (len >= sizeof(s_name_buf))
+				name[sizeof(s_name_buf) - 1] = 0;
 		} else {
 			name[0] = 0;
 		}