Re: [PATCH 1/2] powerpc/powernv: Fix fortify source warnings in opal-prd.c
From: Mahesh J Salgaonkar <mahesh@linux.ibm.com>
Date: 2023-08-23 02:59:27
On 2023-08-22 00:28:19 Tue, Michael Ellerman wrote:
As reported by Mahesh & Aneesh, opal_prd_msg_notifier() triggers a
FORTIFY_SOURCE warning:
memcpy: detected field-spanning write (size 32) of single field "&item->msg" at arch/powerpc/platforms/powernv/opal-prd.c:355 (size 4)
WARNING: CPU: 9 PID: 660 at arch/powerpc/platforms/powernv/opal-prd.c:355 opal_prd_msg_notifier+0x174/0x188 [opal_prd]
NIP opal_prd_msg_notifier+0x174/0x188 [opal_prd]
LR opal_prd_msg_notifier+0x170/0x188 [opal_prd]
Call Trace:
opal_prd_msg_notifier+0x170/0x188 [opal_prd] (unreliable)
notifier_call_chain+0xc0/0x1b0
atomic_notifier_call_chain+0x2c/0x40
opal_message_notify+0xf4/0x2c0
This happens because the copy is targetting item->msg, which is only 4
bytes in size, even though the enclosing item was allocated with extra
space following the msg.
To fix the warning define struct opal_prd_msg with a union of the header
and a flex array, and have the memcpy target the flex array.
Reported-by: Aneesh Kumar K.V <redacted>
Reported-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>Tested-by: Mahesh Salgaonkar <mahesh@linux.ibm.com> Reviewed-by: Mahesh Salgaonkar <mahesh@linux.ibm.com> Thanks, -Mahesh
quoted hunk ↗ jump to hunk
--- arch/powerpc/platforms/powernv/opal-prd.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-)diff --git a/arch/powerpc/platforms/powernv/opal-prd.c b/arch/powerpc/platforms/powernv/opal-prd.c index 113bdb151f68..40e26e9f318f 100644 --- a/arch/powerpc/platforms/powernv/opal-prd.c +++ b/arch/powerpc/platforms/powernv/opal-prd.c@@ -24,13 +24,20 @@ #include <linux/uaccess.h> +struct opal_prd_msg { + union { + struct opal_prd_msg_header header; + DECLARE_FLEX_ARRAY(u8, data); + }; +}; + /* * The msg member must be at the end of the struct, as it's followed by the * message data. */ struct opal_prd_msg_queue_item { - struct list_head list; - struct opal_prd_msg_header msg; + struct list_head list; + struct opal_prd_msg msg; }; static struct device_node *prd_node;@@ -156,7 +163,7 @@ static ssize_t opal_prd_read(struct file *file, char __user *buf, int rc; /* we need at least a header's worth of data */ - if (count < sizeof(item->msg)) + if (count < sizeof(item->msg.header)) return -EINVAL; if (*ppos)@@ -186,7 +193,7 @@ static ssize_t opal_prd_read(struct file *file, char __user *buf, return -EINTR; } - size = be16_to_cpu(item->msg.size); + size = be16_to_cpu(item->msg.header.size); if (size > count) { err = -EINVAL; goto err_requeue;@@ -352,7 +359,7 @@ static int opal_prd_msg_notifier(struct notifier_block *nb, if (!item) return -ENOMEM; - memcpy(&item->msg, msg->params, msg_size); + memcpy(&item->msg.data, msg->params, msg_size); spin_lock_irqsave(&opal_prd_msg_queue_lock, flags); list_add_tail(&item->list, &opal_prd_msg_queue);-- 2.41.0
-- Mahesh J Salgaonkar