If port->mapbase = NULL in serial8250_request_std_resource() , it need
return a error code instead of 0. If uart_set_info() fail to request new
regions by serial8250_request_std_resource() but the return value of
serial8250_request_std_resource() is 0, that The system will mistakenly
considers that port resources are successfully applied for. A null
pointer reference is triggered when the port resource is later invoked.
The problem can also be triggered with the following simple program:
----------
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <errno.h>
struct serial_struct {
int type;
int line;
unsigned int port;
int irq;
int flags;
int xmit_fifo_size;
int custom_divisor;
int baud_base;
unsigned short close_delay;
char io_type;
char reserved_char[1];
int hub6;
unsigned short closing_wait; /* time to wait before closing */
unsigned short closing_wait2; /* no longer used... */
unsigned char *iomem_base;
unsigned short iomem_reg_shift;
unsigned int port_high;
unsigned long iomap_base; /* cookie passed into ioremap */
};
struct serial_struct str;
int main(void)
{
open("/dev/ttyS0", O_RDWR);
ioctl(fd, TIOCGSERIAL, &str);
str.iomem_base = 0;
ioctl(fd, TIOCSSERIAL, str);
return 0;
}
----------
Signed-off-by: Yi Yang <yiyang13@xxxxxxxxxx>
---
drivers/tty/serial/8250/8250_port.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c
index 3e3d784aa628..e1cefa97bdeb 100644
--- a/drivers/tty/serial/8250/8250_port.c
+++ b/drivers/tty/serial/8250/8250_port.c
@@ -2961,8 +2961,10 @@ static int serial8250_request_std_resource(struct uart_8250_port *up)
case UPIO_MEM32BE:
case UPIO_MEM16:
case UPIO_MEM:
- if (!port->mapbase)
+ if (!port->mapbase) {
+ ret = -EFAULT;
break;
+ }
if (!request_mem_region(port->mapbase, size, "serial")) {
ret = -EBUSY;
--
2.17.1
