Re: [PATCH] scsi: Fix a use after free in st_open

["Kai Mäkisara (Kolumbus)"]

> On 11. Mar 2021, at 8.46, Lv Yunlong <lyl2019@xxxxxxxxxxxxxxxx> wrote:
> 
> In st_open, if STp->in_use is true, STp will be freed by
> scsi_tape_put(). However, STp is still used by DEBC_printk()
> after. It is better to DEBC_printk() before scsi_tape_put().
> 
> Signed-off-by: Lv Yunlong <lyl2019@xxxxxxxxxxxxxxxx>

Acked-by: Kai Mäkisara <kai.makisara@xxxxxxxxxxx>

> ---
> drivers/scsi/st.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
> index 841ad2fc369a..9ca536aae784 100644
> --- a/drivers/scsi/st.c
> +++ b/drivers/scsi/st.c
> @@ -1269,8 +1269,8 @@ static int st_open(struct inode *inode, struct file *filp)
> 	spin_lock(&st_use_lock);
> 	if (STp->in_use) {
> 		spin_unlock(&st_use_lock);
> -		scsi_tape_put(STp);
> 		DEBC_printk(STp, "Device already in use.\n");
> +		scsi_tape_put(STp);
> 		return (-EBUSY);
> 	}

Potential problem only when debugging enabled, but should be fixed.

Thanks,
Kai