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 [...] Add a flexible array member to avoid false positive run-time warning. Reported-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.com> Signed-off-by: Mahesh Salgaonkar <mah...@linux.ibm.com> --- arch/powerpc/platforms/powernv/opal-prd.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/platforms/powernv/opal-prd.c b/arch/powerpc/platforms/powernv/opal-prd.c index 113bdb151f687..9e2c4775f75f5 100644 --- a/arch/powerpc/platforms/powernv/opal-prd.c +++ b/arch/powerpc/platforms/powernv/opal-prd.c @@ -30,7 +30,10 @@ */ struct opal_prd_msg_queue_item { struct list_head list; - struct opal_prd_msg_header msg; + union { + struct opal_prd_msg_header msg; + DECLARE_FLEX_ARRAY(__u8, msg_flex); + }; }; static struct device_node *prd_node; @@ -352,7 +355,7 @@ static int opal_prd_msg_notifier(struct notifier_block *nb, if (!item) return -ENOMEM; - memcpy(&item->msg, msg->params, msg_size); + memcpy(&item->msg_flex, msg->params, msg_size); spin_lock_irqsave(&opal_prd_msg_queue_lock, flags); list_add_tail(&item->list, &opal_prd_msg_queue);