[PATCH 6.18 358/752] fs: ntfs3: check return value of indx_find to avoid infinite loop

Sasha Levin
2026-02-28T17:53:08Z

From: Jaehun Gou <p22gone@gmail.com>

[ Upstream commit 1732053c8a6b360e2d5afb1b34fe9779398b072c ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 6d1bf890929d9..050b3709e0204 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;
--
2.51.0