linux-kernel - Re: [PATCH v2 1/4] qla2xxx: Warn if done() or free() are called on an already freed srb

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Date:   Mon, 7 Sep 2020 23:42:32 -0700
From:   Arun Easi <aeasi@...vell.com>
To:     Daniel Wagner <dwagner@...e.de>
CC:     <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "Nilesh Javali" <njavali@...vell.com>,
        Martin Wilck <mwilck@...e.com>
Subject: Re: [PATCH v2 1/4] qla2xxx: Warn if done() or free() are called on
 an already freed srb

On Mon, 31 Aug 2020, 9:18am, Daniel Wagner wrote:

> 
> Emit a warning when ->done or ->free are called on an already freed
> srb. There is a hidden use-after-free bug in the driver which corrupts
> the srb memory pool which originates from the cleanup callbacks. By
> explicitly resetting the callbacks to NULL, we workaround the memory
> corruption.
> 
> An extensive search didn't bring any lights on the real problem. The
> initial idea was to set both pointers to NULL and try to catch invalid
> accesses. But instead the memory corruption was gone and the driver
> didn't crash.
> 
> Signed-off-by: Daniel Wagner <dwagner@...e.de>
> ---
>  drivers/scsi/qla2xxx/qla_init.c   | 10 ++++++++++
>  drivers/scsi/qla2xxx/qla_inline.h |  5 +++++
>  2 files changed, 15 insertions(+)
> 
> diff --git a/drivers/scsi/qla2xxx/qla_init.c b/drivers/scsi/qla2xxx/qla_init.c
> index 57a2d76aa691..9e9360a4aeb5 100644
> --- a/drivers/scsi/qla2xxx/qla_init.c
> +++ b/drivers/scsi/qla2xxx/qla_init.c
> @@ -63,6 +63,16 @@ void qla2x00_sp_free(srb_t *sp)
>  	qla2x00_rel_sp(sp);
>  }
>  
> +void qla2xxx_rel_done_warning(srb_t *sp, int res)
> +{
> +	WARN_ONCE(1, "Calling done() of an already freed srb object\n");
> +}
> +
> +void qla2xxx_rel_free_warning(srb_t *sp)
> +{
> +	WARN_ONCE(1, "Calling free() of an already freed srb object\n");
> +}

Please print the address of srb too for the above two functions.
With that, looks good.

Regards,
-Arun