linux-kernel - [PATCH] fs: ntfs3: check return value of indx

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Message-ID: <20251202105959.1885454-1-p22gone@gmail.com>
Date: Tue,  2 Dec 2025 19:59:59 +0900
From: Jaehun Gou <p22gone@...il.com>
To: almaz.alexandrovich@...agon-software.com
Cc: ntfs3@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Jaehun Gou <p22gone@...il.com>,
	Seunghun Han <kkamagui@...il.com>,
	Jihoon Kwon <kjh010315@...il.com>
Subject: [PATCH] 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@...il.com>
Signed-off-by: Seunghun Han <kkamagui@...il.com>
Co-developed-by: Jihoon Kwon <kjh010315@...il.com>
Signed-off-by: Jihoon Kwon <kjh010315@...il.com>
Signed-off-by: Jaehun Gou <p22gone@...il.com>
---
 fs/ntfs3/index.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/ntfs3/index.c b/fs/ntfs3/index.c
index 6d1bf890929d..050b3709e020 100644
--- a/fs/ntfs3/index.c
+++ b/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;
-- 
2.43.0