[PATCH] fs/ntfs3: Fix slab-out-of-bounds read in ntfs_trim_fs

[PATCH] fs/ntfs3: Fix slab-out-of-bounds read in ntfs_trim_fs

[Abdun Nihaal]

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@syzkaller.appspotmail.com
Signed-off-by: Abdun Nihaal <abdun.nihaal@gmail.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;
 
-- 
2.37.3

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

[Konstantin Komarov via Linux-kernel-mentees]

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@syzkaller.appspotmail.com
> Signed-off-by: Abdun Nihaal <abdun.nihaal@gmail.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!
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