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

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

[Jaehun Gou]

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>
---
 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

Re: [PATCH] fs: ntfs3: check return value of indx_find to avoid infinite loop

[Konstantin Komarov]

On 12/2/25 11:59, Jaehun Gou wrote:

> 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>
> ---
>   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;

Your patch has been applied. Thanks.

Regards,
Konstantin