linux-kernel - Re: [PATCH 2/3] fs/ntfs3: Potential NULL dereference in hdr_find

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Message-ID: <20210824093515.f3kvy4extj76gkjn@kari-VirtualBox>
Date:   Tue, 24 Aug 2021 12:35:15 +0300
From:   Kari Argillander <kari.argillander@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Konstantin Komarov <almaz.alexandrovich@...agon-software.com>,
        ntfs3@...ts.linux.dev, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 2/3] fs/ntfs3: Potential NULL dereference in
 hdr_find_split()

On Tue, Aug 24, 2021 at 10:50:15AM +0300, Dan Carpenter wrote:
> The "e" pointer is dereferenced before it has been checked for NULL.
> Move the dereference after the NULL check to prevent an Oops.
> 
> Fixes: 82cae269cfa9 ("fs/ntfs3: Add initialization of super block")
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

Reviewed-by: Kari Argillander <kari.argillander@...il.com>

> ---
>  fs/ntfs3/index.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ntfs3/index.c b/fs/ntfs3/index.c
> index 07d6dee0a4ba..489e0fffbc75 100644
> --- a/fs/ntfs3/index.c
> +++ b/fs/ntfs3/index.c
> @@ -556,11 +556,12 @@ static const struct NTFS_DE *hdr_find_split(const struct INDEX_HDR *hdr)
>  	size_t o;
>  	const struct NTFS_DE *e = hdr_first_de(hdr);
>  	u32 used_2 = le32_to_cpu(hdr->used) >> 1;
> -	u16 esize = le16_to_cpu(e->size);
> +	u16 esize;
>  
>  	if (!e || de_is_last(e))
>  		return NULL;
>  
> +	esize = le16_to_cpu(e->size);
>  	for (o = le32_to_cpu(hdr->de_off) + esize; o < used_2; o += esize) {
>  		const struct NTFS_DE *p = e;