staging: gdm724x: Correction of variable usage after applying ALIGN()

Fix regression introduced by commit <29ef8a53542a>. After it writing
AT commands to /dev/GCT-ATM0 is unsuccessful (no echo, no response)
and dmesg show "gdmtty: invalid payload : 1 16 f011".

Before that commit value of dummy_cnt was only a padding size. After using
ALIGN() this value is increased by its first argument. So the following
usage of this variable needs correction.

Signed-off-by: Sławomir Demeszko <s.demeszko@wireless-instruments.com>
Cc: stable <stable@vger.kernel.org> # 3.14+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 7 insertions, 9 deletions

diff --git a/drivers/staging/gdm724x/gdm_mux.c b/drivers/staging/gdm724x/gdm_mux.c
index 8199b0a697bb..1cf24e4edf25 100644
--- a/drivers/staging/gdm724x/gdm_mux.c
+++ b/drivers/staging/gdm724x/gdm_mux.c
@@ -158,7 +158,7 @@ static int up_to_host(struct mux_rx *r)
         unsigned int start_flag;
         unsigned int payload_size;
         unsigned short packet_type;
-        int dummy_cnt;
+        int total_len;
         u32 packet_size_sum = r->offset;
         int index;
         int ret = TO_HOST_INVALID_PACKET;
@@ -176,10 +176,10 @@ static int up_to_host(struct mux_rx *r)
                         break;
                 }
 
-                dummy_cnt = ALIGN(MUX_HEADER_SIZE + payload_size, 4);
+                total_len = ALIGN(MUX_HEADER_SIZE + payload_size, 4);
 
                 if (len - packet_size_sum <
-                        MUX_HEADER_SIZE + payload_size + dummy_cnt) {
+                        total_len) {
                         pr_err("invalid payload : %d %d %04x\n",
                                payload_size, len, packet_type);
                         break;
@@ -202,7 +202,7 @@ static int up_to_host(struct mux_rx *r)
                         break;
                 }
 
-                packet_size_sum += MUX_HEADER_SIZE + payload_size + dummy_cnt;
+                packet_size_sum += total_len;
                 if (len - packet_size_sum <= MUX_HEADER_SIZE + 2) {
                         ret = r->callback(NULL,
                                         0,
@@ -361,7 +361,6 @@ static int gdm_mux_send(void *priv_dev, void *data, int len, int tty_index,
         struct mux_pkt_header *mux_header;
         struct mux_tx *t = NULL;
         static u32 seq_num = 1;
-        int dummy_cnt;
         int total_len;
         int ret;
         unsigned long flags;
@@ -374,9 +373,7 @@ static int gdm_mux_send(void *priv_dev, void *data, int len, int tty_index,
 
         spin_lock_irqsave(&mux_dev->write_lock, flags);
 
-        dummy_cnt = ALIGN(MUX_HEADER_SIZE + len, 4);
-
-        total_len = len + MUX_HEADER_SIZE + dummy_cnt;
+        total_len = ALIGN(MUX_HEADER_SIZE + len, 4);
 
         t = alloc_mux_tx(total_len);
         if (!t) {
@@ -392,7 +389,8 @@ static int gdm_mux_send(void *priv_dev, void *data, int len, int tty_index,
         mux_header->packet_type = __cpu_to_le16(packet_type[tty_index]);
 
         memcpy(t->buf+MUX_HEADER_SIZE, data, len);
-        memset(t->buf+MUX_HEADER_SIZE+len, 0, dummy_cnt);
+        memset(t->buf+MUX_HEADER_SIZE+len, 0, total_len - MUX_HEADER_SIZE -
+               len);
 
         t->len = total_len;
         t->callback = cb;