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Subject[PATCH] pcmcia: synclink_cs: fix potential tty NULL dereference
Date
tty_port_tty_get() can return NULL after port hangup that may happen anytime.
The patch adds checks that tty_port_tty_get() returns nonNULL around places
where tty is actually used.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
---
drivers/char/pcmcia/synclink_cs.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/char/pcmcia/synclink_cs.c b/drivers/char/pcmcia/synclink_cs.c
index 0a484b4..13c9747 100644
--- a/drivers/char/pcmcia/synclink_cs.c
+++ b/drivers/char/pcmcia/synclink_cs.c
@@ -891,6 +891,9 @@ static void rx_ready_async(MGSLPC_INFO *info, int tcd, struct tty_struct *tty)
int work = 0;
struct mgsl_icount *icount = &info->icount;

+ if (!tty)
+ return;
+
if (tcd) {
/* early termination, get FIFO count from RBCL register */
fifo_count = (unsigned char)(read_reg(info, CHA+RBCL) & 0x1f);
@@ -980,7 +983,7 @@ static void tx_done(MGSLPC_INFO *info, struct tty_struct *tty)
else
#endif
{
- if (tty->stopped || tty->hw_stopped) {
+ if (tty && (tty->stopped || tty->hw_stopped)) {
tx_stop(info);
return;
}
@@ -1000,7 +1003,7 @@ static void tx_ready(MGSLPC_INFO *info, struct tty_struct *tty)
if (!info->tx_active)
return;
} else {
- if (tty->stopped || tty->hw_stopped) {
+ if (tty && (tty->stopped || tty->hw_stopped)) {
tx_stop(info);
return;
}
@@ -1050,13 +1053,12 @@ static void cts_change(MGSLPC_INFO *info, struct tty_struct *tty)
wake_up_interruptible(&info->status_event_wait_q);
wake_up_interruptible(&info->event_wait_q);

- if (info->port.flags & ASYNC_CTS_FLOW) {
+ if (tty && (info->port.flags & ASYNC_CTS_FLOW)) {
if (tty->hw_stopped) {
if (info->serial_signals & SerialSignal_CTS) {
if (debug_level >= DEBUG_LEVEL_ISR)
printk("CTS tx start...");
- if (tty)
- tty->hw_stopped = 0;
+ tty->hw_stopped = 0;
tx_start(info, tty);
info->pending_bh |= BH_TRANSMIT;
return;
@@ -1065,8 +1067,7 @@ static void cts_change(MGSLPC_INFO *info, struct tty_struct *tty)
if (!(info->serial_signals & SerialSignal_CTS)) {
if (debug_level >= DEBUG_LEVEL_ISR)
printk("CTS tx stop...");
- if (tty)
- tty->hw_stopped = 1;
+ tty->hw_stopped = 1;
tx_stop(info);
}
}
--
1.7.9.5


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