2022-10-01 07:33:28

by Abdun Nihaal

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

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: [email protected]
Signed-off-by: Abdun Nihaal <[email protected]>
---
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

2022-11-12 19:11:37

by Konstantin Komarov

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: [email protected]
> Signed-off-by: Abdun Nihaal <[email protected]>
> ---
> 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!