linux-kernel - Re: [PATCH] ntfs3: Fix attr_punch_hole() null pointer derenference

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Message-ID: <784f82c4-de71-b8c3-afd6-468869a369af@paragon-software.com>
Date:   Fri, 30 Sep 2022 18:44:30 +0300
From:   Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
To:     Alon Zahavi <zahavi.alon@...il.com>, <ntfs3@...ts.linux.dev>,
        <linux-kernel@...r.kernel.org>
CC:     Tal Lossos <tallossos@...il.com>
Subject: Re: [PATCH] ntfs3: Fix attr_punch_hole() null pointer derenference



On 8/15/22 14:07, Alon Zahavi wrote:
> From: Alon Zahavi <zahavi.alon@...il.com>
> 
> The bug occours due to a misuse of `attr` variable instead of `attr_b`.
> `attr` is being initialized as NULL, then being derenfernced
> as `attr->res.data_size`.
> 
> This bug causes a crash of the ntfs3 driver itself,
> If compiled directly to the kernel, it crashes the whole system.
> 
> Signed-off-by: Alon Zahavi <zahavi.alon@...il.com>
> Co-developed-by: Tal Lossos <tallossos@...il.com>
> Signed-off-by: Tal Lossos <tallossos@...il.com>
> ---
>   fs/ntfs3/attrib.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ntfs3/attrib.c b/fs/ntfs3/attrib.c
> index e8c00dda42ad..4e74bc8f01ed 100644
> --- a/fs/ntfs3/attrib.c
> +++ b/fs/ntfs3/attrib.c
> @@ -1949,7 +1949,7 @@ int attr_punch_hole(struct ntfs_inode *ni, u64 vbo, u64 bytes, u32 *frame_size)
>   		return -ENOENT;
>   
>   	if (!attr_b->non_res) {
> -		u32 data_size = le32_to_cpu(attr->res.data_size);
> +		u32 data_size = le32_to_cpu(attr_b->res.data_size);
>   		u32 from, to;
>   
>   		if (vbo > data_size)

Applied, thanks!