[PATCH] Char: mxser_new, alter locking in isr

Avoid oopsing when stress-testing open/close -- port->tty is NULL sometimes,
but is expected to be non-NULL, since dereferencing.  Receive/transmit chars
iff ASYNC_CLOSING is not set and ASYNC_INITIALIZED is set.  Thanks Sergei for
pointing this out and testing.

Cc: Sergei Organov <osv@javad.com>
Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 13 deletions

diff --git a/drivers/char/mxser_new.c b/drivers/char/mxser_new.c
index 8da883340dd6..ec61cf81b7e6 100644
--- a/drivers/char/mxser_new.c
+++ b/drivers/char/mxser_new.c
@@ -2073,9 +2073,6 @@ static void mxser_receive_chars(struct mxser_port *port, int *status)
         int cnt = 0;
         int recv_room;
         int max = 256;
-        unsigned long flags;
-
-        spin_lock_irqsave(&port->slock, flags);
 
         recv_room = tty->receive_room;
         if ((recv_room == 0) && (!port->ldisc_stop_rx))
@@ -2159,7 +2156,6 @@ end_intr:
         mxvar_log.rxcnt[port->tty->index] += cnt;
         port->mon_data.rxcnt += cnt;
         port->mon_data.up_rxcnt += cnt;
-        spin_unlock_irqrestore(&port->slock, flags);
 
         tty_flip_buffer_push(tty);
 }
@@ -2167,9 +2163,6 @@ end_intr:
 static void mxser_transmit_chars(struct mxser_port *port)
 {
         int count, cnt;
-        unsigned long flags;
-
-        spin_lock_irqsave(&port->slock, flags);
 
         if (port->x_char) {
                 outb(port->x_char, port->ioaddr + UART_TX);
@@ -2178,11 +2171,11 @@ static void mxser_transmit_chars(struct mxser_port *port)
                 port->mon_data.txcnt++;
                 port->mon_data.up_txcnt++;
                 port->icount.tx++;
-                goto unlock;
+                return;
         }
 
         if (port->xmit_buf == 0)
-                goto unlock;
+                return;
 
         if ((port->xmit_cnt <= 0) || port->tty->stopped ||
                         (port->tty->hw_stopped &&
@@ -2190,7 +2183,7 @@ static void mxser_transmit_chars(struct mxser_port *port)
                         (!port->board->chip_flag))) {
                 port->IER &= ~UART_IER_THRI;
                 outb(port->IER, port->ioaddr + UART_IER);
-                goto unlock;
+                return;
         }
 
         cnt = port->xmit_cnt;
@@ -2215,8 +2208,6 @@ static void mxser_transmit_chars(struct mxser_port *port)
                 port->IER &= ~UART_IER_THRI;
                 outb(port->IER, port->ioaddr + UART_IER);
         }
-unlock:
-        spin_unlock_irqrestore(&port->slock, flags);
 }
 
 /*
@@ -2257,12 +2248,16 @@ static irqreturn_t mxser_interrupt(int irq, void *dev_id)
                         port = &brd->ports[i];
 
                         int_cnt = 0;
+                        spin_lock(&port->slock);
                         do {
                                 iir = inb(port->ioaddr + UART_IIR);
                                 if (iir & UART_IIR_NO_INT)
                                         break;
                                 iir &= MOXA_MUST_IIR_MASK;
-                                if (!port->tty) {
+                                if (!port->tty ||
+                                                (port->flags & ASYNC_CLOSING) ||
+                                                !(port->flags &
+                                                        ASYNC_INITIALIZED)) {
                                         status = inb(port->ioaddr + UART_LSR);
                                         outb(0x27, port->ioaddr + UART_FCR);
                                         inb(port->ioaddr + UART_MSR);
@@ -2308,6 +2303,7 @@ static irqreturn_t mxser_interrupt(int irq, void *dev_id)
                                                 mxser_transmit_chars(port);
                                 }
                         } while (int_cnt++ < MXSER_ISR_PASS_LIMIT);
+                        spin_unlock(&port->slock);
                 }
                 if (pass_counter++ > MXSER_ISR_PASS_LIMIT)
                         break;  /* Prevent infinite loops */