n_gsm.c: add tx_lock in gsm_send

All the call to gsm->output should be in the tx_lock,
that could avoid potential race from MUX level. But
we have no tx_lock in gsm_send.

This patch is to add tx_lock in gsm_send.

Signed-off-by: xiaojin <jin.xiao@intel.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index dcc0430a49c8..4572117988f8 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -573,6 +573,7 @@ static void gsm_send(struct gsm_mux *gsm, int addr, int cr, int control)
         int len;
         u8 cbuf[10];
         u8 ibuf[3];
+        unsigned long flags;
 
         switch (gsm->encoding) {
         case 0:
@@ -602,7 +603,9 @@ static void gsm_send(struct gsm_mux *gsm, int addr, int cr, int control)
                 WARN_ON(1);
                 return;
         }
+        spin_lock_irqsave(&gsm->tx_lock, flags);
         gsm->output(gsm, cbuf, len);
+        spin_unlock_irqrestore(&gsm->tx_lock, flags);
         gsm_print_packet("-->", addr, cr, control, NULL, 0);
 }