2021-03-11 06:48:35

by Lv Yunlong

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

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 <[email protected]>
---
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);
}

--
2.25.1

2021-03-11 18:28:27

by Kai Mäkisara (Kolumbus)

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

> On 11. Mar 2021, at 8.46, Lv Yunlong <[email protected]> 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 <[email protected]>

Acked-by: Kai Mäkisara <[email protected]>

> ---
> 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

2021-03-16 11:26:04

by Martin K. Petersen

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

On Wed, 10 Mar 2021 22:46:36 -0800, Lv Yunlong 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().

Applied to 5.12/scsi-fixes, thanks!

[1/1] scsi: Fix a use after free in st_open
https://git.kernel.org/mkp/scsi/c/c8c165dea4c8

--
Martin K. Petersen Oracle Linux Engineering