fc_exch_release(ep) will decrease the ep's reference count. When the
reference count reaches zero, it is freed. But ep is still used in the
following code, which will lead to a use after free.

We should return the function after the call of fc_exch_release() to
avoid use after free.

Signed-off-by: Jianglei Nie <niejianglei2021@163.com>
---
 drivers/scsi/libfc/fc_exch.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/scsi/libfc/fc_exch.c b/drivers/scsi/libfc/fc_exch.c
index 841000445b9a..aa223db4cf53 100644
--- a/drivers/scsi/libfc/fc_exch.c
+++ b/drivers/scsi/libfc/fc_exch.c
@@ -1701,6 +1701,7 @@ static void fc_exch_abts_resp(struct fc_exch *ep, struct fc_frame *fp)
 	if (cancel_delayed_work_sync(&ep->timeout_work)) {
 		FC_EXCH_DBG(ep, "Exchange timer canceled due to ABTS response\n");
 		fc_exch_release(ep);	/* release from pending timer hold */
+		return;
 	}
 
 	spin_lock_bh(&ep->ex_lock);
-- 
2.25.1

On 3/3/22 02:51, Jianglei Nie wrote:
> fc_exch_release(ep) will decrease the ep's reference count. When the
> reference count reaches zero, it is freed. But ep is still used in the
> following code, which will lead to a use after free.
> 
> We should return the function after the call of fc_exch_release() to
> avoid use after free.
> 
> Signed-off-by: Jianglei Nie <niejianglei2021@163.com>
> ---
>   drivers/scsi/libfc/fc_exch.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/scsi/libfc/fc_exch.c b/drivers/scsi/libfc/fc_exch.c
> index 841000445b9a..aa223db4cf53 100644
> --- a/drivers/scsi/libfc/fc_exch.c
> +++ b/drivers/scsi/libfc/fc_exch.c
> @@ -1701,6 +1701,7 @@ static void fc_exch_abts_resp(struct fc_exch *ep, struct fc_frame *fp)
>   	if (cancel_delayed_work_sync(&ep->timeout_work)) {
>   		FC_EXCH_DBG(ep, "Exchange timer canceled due to ABTS response\n");
>   		fc_exch_release(ep);	/* release from pending timer hold */
> +		return;
>   	}
>   
>   	spin_lock_bh(&ep->ex_lock);

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer

Jianglei,

> fc_exch_release(ep) will decrease the ep's reference count. When the
> reference count reaches zero, it is freed. But ep is still used in the
> following code, which will lead to a use after free.

Applied to 5.18/scsi-staging, thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering

On Thu, 3 Mar 2022 09:51:15 +0800, Jianglei Nie wrote:

> fc_exch_release(ep) will decrease the ep's reference count. When the
> reference count reaches zero, it is freed. But ep is still used in the
> following code, which will lead to a use after free.
> 
> We should return the function after the call of fc_exch_release() to
> avoid use after free.
> 
> [...]

Applied to 5.18/scsi-queue, thanks!

[1/1] scsi: libfc: Fix use after free in fc_exch_abts_resp()
      https://git.kernel.org/mkp/scsi/c/271add11994b

-- 
Martin K. Petersen	Oracle Linux Engineering