[PATCH v2] powernv/opal-prd: Silence memcpy() run-time false positive warnings

[Joel Stanley]

On Fri, 7 Jul 2023 at 05:11, Mahesh Salgaonkar <mahesh at linux.ibm.com> wrote:
>
> opal_prd_msg_notifier extracts the opal prd message size from the message
> header and uses it for allocating opal_prd_msg_queue_item that includes
> the correct message size to be copied. However, while running under
> CONFIG_FORTIFY_SOURCE=y, it triggers following run-time warning:
>
> [ 6458.234352] memcpy: detected field-spanning write (size 32) of single field "&item->msg" at arch/powerpc/platforms/powernv/opal-prd.c:355 (size 4)
> [ 6458.234390] WARNING: CPU: 9 PID: 660 at arch/powerpc/platforms/powernv/opal-prd.c:355 opal_prd_msg_notifier+0x174/0x188 [opal_prd]
> [...]
> [ 6458.234709] NIP [c00800000e0c0e6c] opal_prd_msg_notifier+0x174/0x188 [opal_prd]
> [ 6458.234723] LR [c00800000e0c0e68] opal_prd_msg_notifier+0x170/0x188 [opal_prd]
> [ 6458.234736] Call Trace:
> [ 6458.234742] [c0000002acb23c10] [c00800000e0c0e68] opal_prd_msg_notifier+0x170/0x188 [opal_prd] (unreliable)
> [ 6458.234759] [c0000002acb23ca0] [c00000000019ccc0] notifier_call_chain+0xc0/0x1b0
> [ 6458.234774] [c0000002acb23d00] [c00000000019ceac] atomic_notifier_call_chain+0x2c/0x40
> [ 6458.234788] [c0000002acb23d20] [c0000000000d69b4] opal_message_notify+0xf4/0x2c0
> [...]
>
> Split the copy to avoid false positive run-time warning.
>
> Reported-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
> Signed-off-by: Mahesh Salgaonkar <mahesh at linux.ibm.com>

I hit this on a box running the Ubuntu 6.2.0-27-generic kernel.

Do we plan on merging this fix?



> ---
> Change from v1:
> - Rework the memcpy to copy message header and rest of the message
>   separately without adding flex array.
> ---
>  arch/powerpc/platforms/powernv/opal-prd.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/platforms/powernv/opal-prd.c b/arch/powerpc/platforms/powernv/opal-prd.c
> index 113bdb151f687..a068cbc4d43c0 100644
> --- a/arch/powerpc/platforms/powernv/opal-prd.c
> +++ b/arch/powerpc/platforms/powernv/opal-prd.c
> @@ -352,7 +352,9 @@ static int opal_prd_msg_notifier(struct notifier_block *nb,
>         if (!item)
>                 return -ENOMEM;
>
> -       memcpy(&item->msg, msg->params, msg_size);
> +       item->msg = *hdr;
> +       hdr++;
> +       memcpy((char *)&item->msg + sizeof(*hdr), hdr, msg_size - sizeof(*hdr));
>
>         spin_lock_irqsave(&opal_prd_msg_queue_lock, flags);
>         list_add_tail(&item->list, &opal_prd_msg_queue);
>
>