linux-kernel - [PATCH] fs: ntfs3: fix infinite loop triggered by zero-sized ATTR

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Message-ID: <20251202110146.1886202-1-p22gone@gmail.com>
Date: Tue,  2 Dec 2025 20:01:46 +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: fix infinite loop triggered by zero-sized ATTR_LIST

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

A malformed NTFS image can cause an infinite loop when an ATTR_LIST attribute
indicates a zero data size while the driver allocates memory for it.

When ntfs_load_attr_list() processes a resident ATTR_LIST with data_size set
to zero, it still allocates memory because of al_aligned(0). This creates an
inconsistent state where ni->attr_list.size is zero, but ni->attr_list.le is
non-null. This causes ni_enum_attr_ex to incorrectly assume that no attribute
list exists and enumerates only the primary MFT record. When it finds
ATTR_LIST, the code reloads it and restarts the enumeration, repeating
indefinitely. The mount operation never completes, hanging the kernel thread.

This patch adds validation to ensure that data_size is non-zero before memory
allocation. When a zero-sized ATTR_LIST is detected, the function returns
-EINVAL, preventing a DoS vulnerability.

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/attrlist.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/fs/ntfs3/attrlist.c b/fs/ntfs3/attrlist.c
index a4d74bed74fa..098bd7e8c3d6 100644
--- a/fs/ntfs3/attrlist.c
+++ b/fs/ntfs3/attrlist.c
@@ -52,6 +52,11 @@ int ntfs_load_attr_list(struct ntfs_inode *ni, struct ATTRIB *attr)

 	if (!attr->non_res) {
 		lsize = le32_to_cpu(attr->res.data_size);
+		if (!lsize) {
+			err = -EINVAL;
+			goto out;
+		}
+
 		/* attr is resident: lsize < record_size (1K or 4K) */
 		le = kvmalloc(al_aligned(lsize), GFP_KERNEL);
 		if (!le) {
@@ -66,6 +71,10 @@ int ntfs_load_attr_list(struct ntfs_inode *ni, struct ATTRIB *attr)
 		u16 run_off = le16_to_cpu(attr->nres.run_off);

 		lsize = le64_to_cpu(attr->nres.data_size);
+		if (!lsize) {
+			err = -EINVAL;
+			goto out;
+		}

 		run_init(&ni->attr_list.run);

-- 
2.43.0