firewire: check cdev response length

Add a check that the data length in the SEND_RESPONSE ioctl is correct.
Incidentally, this also fixes the previously wrong response length of
software-handled lock requests.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

3 files changed, 44 insertions, 4 deletions

diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
index 9d1a1a1a83c9..50332b84f49a 100644
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -756,9 +756,12 @@ static int ioctl_send_response(struct client *client, union ioctl_arg *arg)
         if (is_fcp_request(r->request))
                 goto out;
 
-        if (a->length < r->length)
-                r->length = a->length;
-        if (copy_from_user(r->data, u64_to_uptr(a->data), r->length)) {
+        if (a->length != fw_get_response_length(r->request)) {
+                ret = -EINVAL;
+                kfree(r->request);
+                goto out;
+        }
+        if (copy_from_user(r->data, u64_to_uptr(a->data), a->length)) {
                 ret = -EFAULT;
                 kfree(r->request);
                 goto out;
diff --git a/drivers/firewire/core-transaction.c b/drivers/firewire/core-transaction.c
index fdc33ff06dc1..4fd5c3b2128e 100644
--- a/drivers/firewire/core-transaction.c
+++ b/drivers/firewire/core-transaction.c
@@ -580,6 +580,41 @@ static void free_response_callback(struct fw_packet *packet,
         kfree(request);
 }
 
+int fw_get_response_length(struct fw_request *r)
+{
+        int tcode, ext_tcode, data_length;
+
+        tcode = HEADER_GET_TCODE(r->request_header[0]);
+
+        switch (tcode) {
+        case TCODE_WRITE_QUADLET_REQUEST:
+        case TCODE_WRITE_BLOCK_REQUEST:
+                return 0;
+
+        case TCODE_READ_QUADLET_REQUEST:
+                return 4;
+
+        case TCODE_READ_BLOCK_REQUEST:
+                data_length = HEADER_GET_DATA_LENGTH(r->request_header[3]);
+                return data_length;
+
+        case TCODE_LOCK_REQUEST:
+                ext_tcode = HEADER_GET_EXTENDED_TCODE(r->request_header[3]);
+                data_length = HEADER_GET_DATA_LENGTH(r->request_header[3]);
+                switch (ext_tcode) {
+                case EXTCODE_FETCH_ADD:
+                case EXTCODE_LITTLE_ADD:
+                        return data_length;
+                default:
+                        return data_length / 2;
+                }
+
+        default:
+                WARN(1, KERN_ERR "wrong tcode %d", tcode);
+                return 0;
+        }
+}
+
 void fw_fill_response(struct fw_packet *response, u32 *request_header,
                       int rcode, void *payload, size_t length)
 {
@@ -713,7 +748,8 @@ void fw_send_response(struct fw_card *card,
 
         if (rcode == RCODE_COMPLETE)
                 fw_fill_response(&request->response, request->request_header,
-                                 rcode, request->data, request->length);
+                                 rcode, request->data,
+                                 fw_get_response_length(request));
         else
                 fw_fill_response(&request->response, request->request_header,
                                  rcode, NULL, 0);
diff --git a/drivers/firewire/core.h b/drivers/firewire/core.h
index 0ecfcd95f4c5..25a72e57a0cd 100644
--- a/drivers/firewire/core.h
+++ b/drivers/firewire/core.h
@@ -218,6 +218,7 @@ static inline bool is_next_generation(int new_generation, int old_generation)
 
 void fw_core_handle_request(struct fw_card *card, struct fw_packet *request);
 void fw_core_handle_response(struct fw_card *card, struct fw_packet *packet);
+int fw_get_response_length(struct fw_request *request);
 void fw_fill_response(struct fw_packet *response, u32 *request_header,
                       int rcode, void *payload, size_t length);
 void fw_send_phy_config(struct fw_card *card,