[PATCH 11/17] mpi3mr: Fix out-of-bounds read of event data

[Chandrakanth Patil <chandrakanth.patil@broadcom.com>]

The event data length from the reply is used as is, both when caching
log data and when sizing the buffer handed to the bottom half. A length
larger than the frame makes both of them read past the end of it.

Clamp the length to what the frame can hold.

Fixes: 13ef29ea4aa0 ("scsi: mpi3mr: Add support for device add/remove event handling")
Fixes: d0d19250ed81 ("scsi: mpi3mr: Rename log data save helper to reflect threaded/BH context")
Signed-off-by: Chandrakanth Patil <chandrakanth.patil@broadcom.com>
---
 drivers/scsi/mpi3mr/mpi3mr_os.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/mpi3mr/mpi3mr_os.c b/drivers/scsi/mpi3mr/mpi3mr_os.c
index 94625e5f6af8..6d4ddc78bcd0 100644
--- a/drivers/scsi/mpi3mr/mpi3mr_os.c
+++ b/drivers/scsi/mpi3mr/mpi3mr_os.c
@@ -3109,7 +3109,7 @@ void mpi3mr_add_event_wait_for_device_refresh(struct mpi3mr_ioc *mrioc)
 void mpi3mr_os_handle_events(struct mpi3mr_ioc *mrioc,
 	struct mpi3_event_notification_reply *event_reply)
 {
-	u16 evt_type, sz;
+	u16 evt_type, sz, avail_reply_room;
 	struct mpi3mr_fwevt *fwevt = NULL;
 	bool ack_req = 0, process_evt_bh = 0;
 
@@ -3170,7 +3170,12 @@ void mpi3mr_os_handle_events(struct mpi3mr_ioc *mrioc,
 	case MPI3_EVENT_DEVICE_INFO_CHANGED:
 	case MPI3_EVENT_LOG_DATA:
 
-		sz = event_reply->event_data_length * 4;
+		if (mrioc->reply_sz > offsetof(struct mpi3_event_notification_reply, event_data))
+			avail_reply_room = mrioc->reply_sz -
+			    offsetof(struct mpi3_event_notification_reply, event_data);
+		else
+			avail_reply_room = 0;
+		sz = min_t(u16, event_reply->event_data_length * 4, avail_reply_room);
 		mpi3mr_app_save_logdata_th(mrioc,
 			(char *)event_reply->event_data, sz);
 		break;
@@ -3204,7 +3209,12 @@ void mpi3mr_os_handle_events(struct mpi3mr_ioc *mrioc,
 		dprint_event_th(mrioc,
 		    "scheduling bottom half handler for event(0x%02x) - (0x%08x), ack_required=%d\n",
 		    evt_type, le32_to_cpu(event_reply->event_context), ack_req);
-		sz = event_reply->event_data_length * 4;
+		if (mrioc->reply_sz > offsetof(struct mpi3_event_notification_reply, event_data))
+			avail_reply_room = mrioc->reply_sz -
+			    offsetof(struct mpi3_event_notification_reply, event_data);
+		else
+			avail_reply_room = 0;
+		sz = min_t(u16, event_reply->event_data_length * 4, avail_reply_room);
 		fwevt = mpi3mr_alloc_fwevt(sz);
 		if (!fwevt) {
 			dprint_event_th(mrioc,