5.15-stable review patch. If anyone has any objections, please let me know.
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From: Michael Ellerman mpe@ellerman.id.au
commit feea65a338e52297b68ceb688eaf0ffc50310a83 upstream.
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 targeting 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" aneesh.kumar@linux.ibm.com Reported-by: Mahesh Salgaonkar mahesh@linux.ibm.com Tested-by: Mahesh Salgaonkar mahesh@linux.ibm.com Reviewed-by: Mahesh Salgaonkar mahesh@linux.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://msgid.link/20230821142820.497107-1-mpe@ellerman.id.au Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/powerpc/platforms/powernv/opal-prd.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-)
--- 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 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 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 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);