linux-kernel - Re: [PATCH] fs/ntfs3: Fix slab-out-of-bounds read in ntfs_trim

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Date:   Sat, 12 Nov 2022 21:06:53 +0300
From:   Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
To:     Abdun Nihaal <abdun.nihaal@...il.com>
CC:     <ntfs3@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
        <skhan@...uxfoundation.org>,
        <linux-kernel-mentees@...ts.linuxfoundation.org>,
        <syzbot+b892240eac461e488d51@...kaller.appspotmail.com>
Subject: Re: [PATCH] fs/ntfs3: Fix slab-out-of-bounds read in ntfs_trim_fs



On 10/1/22 10:00, Abdun Nihaal wrote:
> Syzbot reports an out of bound access in ntfs_trim_fs.
> The cause of this is using a loop termination condition that compares
> window index (iw) with wnd->nbits instead of wnd->nwnd, due to which the
> index used for wnd->free_bits exceeds the size of the array allocated.
> 
> Fix the loop condition.
> 
> Fixes: 3f3b442b5ad2 ("fs/ntfs3: Add bitmap")
> Link: https://syzkaller.appspot.com/bug?extid=b892240eac461e488d51
> Reported-by: syzbot+b892240eac461e488d51@...kaller.appspotmail.com
> Signed-off-by: Abdun Nihaal <abdun.nihaal@...il.com>
> ---
>   fs/ntfs3/bitmap.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ntfs3/bitmap.c b/fs/ntfs3/bitmap.c
> index 1675c9a69788..629c1ee97268 100644
> --- a/fs/ntfs3/bitmap.c
> +++ b/fs/ntfs3/bitmap.c
> @@ -1424,7 +1424,7 @@ int ntfs_trim_fs(struct ntfs_sb_info *sbi, struct fstrim_range *range)
>   
>   	down_read_nested(&wnd->rw_lock, BITMAP_MUTEX_CLUSTERS);
>   
> -	for (; iw < wnd->nbits; iw++, wbit = 0) {
> +	for (; iw < wnd->nwnd; iw++, wbit = 0) {
>   		CLST lcn_wnd = iw * wbits;
>   		struct buffer_head *bh;
>   

Thanks for patch, applied!