fs: ntfs3: check return value of indx_find to avoid infinite loop

We found an infinite loop bug in the ntfs3 file system that can lead to a
Denial-of-Service (DoS) condition.

A malformed dentry in the ntfs3 filesystem can cause the kernel to hang
during the lookup operations. By setting the HAS_SUB_NODE flag in an
INDEX_ENTRY within a directory's INDEX_ALLOCATION block and manipulating the
VCN pointer, an attacker can cause the indx_find() function to repeatedly
read the same block, allocating 4 KB of memory each time. The kernel lacks
VCN loop detection and depth limits, causing memory exhaustion and an OOM
crash.

This patch adds a return value check for fnd_push() to prevent a memory
exhaustion vulnerability caused by infinite loops. When the index exceeds the
size of the fnd->nodes array, fnd_push() returns -EINVAL. The indx_find()
function checks this return value and stops processing, preventing further
memory allocation.

Co-developed-by: Seunghun Han <kkamagui@gmail.com>
Signed-off-by: Seunghun Han <kkamagui@gmail.com>
Co-developed-by: Jihoon Kwon <kjh010315@gmail.com>
Signed-off-by: Jihoon Kwon <kjh010315@gmail.com>
Signed-off-by: Jaehun Gou <p22gone@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3/index.c

@@ -1190,7 +1190,12 @@ int indx_find(struct ntfs_index *indx, struct ntfs_inode *ni,
 			return -EINVAL;
 		}
 
-		fnd_push(fnd, node, e);
+		err = fnd_push(fnd, node, e);
+
+		if (err) {
+			put_indx_node(node);
+			return err;
+		}
 	}
 
 	*entry = e;