On 3/15/23 12:31, Kirill A. Shutemov wrote:
> MAX_ORDER is not inclusive: the maximum allocation order buddy allocator
> can deliver is MAX_ORDER-1.
>
> Fix MAX_ORDER usage in floppy code.
>
> Also allocation buffer exactly PAGE_SIZE << MAX_ORDER bytes is okay. Fix
> MAX_LEN check.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Denis Efremov <efremov@xxxxxxxxx>
> ---
> drivers/block/floppy.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
> index 487840e3564d..90d2dfb6448e 100644
> --- a/drivers/block/floppy.c
> +++ b/drivers/block/floppy.c
> @@ -3079,7 +3079,7 @@ static void raw_cmd_free(struct floppy_raw_cmd **ptr)
> }
> }
>
> -#define MAX_LEN (1UL << MAX_ORDER << PAGE_SHIFT)
> +#define MAX_LEN (1UL << (MAX_ORDER - 1) << PAGE_SHIFT)
>
> static int raw_cmd_copyin(int cmd, void __user *param,
> struct floppy_raw_cmd **rcmd)
> @@ -3108,7 +3108,7 @@ static int raw_cmd_copyin(int cmd, void __user *param,
> ptr->resultcode = 0;
>
> if (ptr->flags & (FD_RAW_READ | FD_RAW_WRITE)) {
> - if (ptr->length <= 0 || ptr->length >= MAX_LEN)
> + if (ptr->length <= 0 || ptr->length > MAX_LEN)
> return -EINVAL;
> ptr->kernel_data = (char *)fd_dma_mem_alloc(ptr->length);
> fallback_on_nodma_alloc(&ptr->kernel_data, ptr->length);
