usb: gadget: eliminate NULL pointer dereference (bugfix)

commit 92b0abf80c5c5f0e0d71d1309688a330fd74731b upstream.

usb: gadget: eliminate NULL pointer dereference (bugfix)

This patch fixes a bug which causes NULL pointer dereference in
ffs_ep0_ioctl. The bug happens when the FunctionFS is not bound (either
has not been bound yet or has been bound and then unbound) and can be
reproduced with running the following commands:

$ insmod g_ffs.ko
$ mount -t functionfs func /dev/usbgadget
$ ./null

where null.c is:

#include <fcntl.h>
#include <linux/usb/functionfs.h>

int main(void)
{
	int fd = open("/dev/usbgadget/ep0", O_RDWR);
	ioctl(fd, FUNCTIONFS_CLEAR_HALT);

	return 0;
}

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/usb/gadget/f_fs.c b/drivers/usb/gadget/f_fs.c
index acb38004eec08ba72819477df0af6eacd00bcd34..0e641a1eabd02cf59017448870d319e4688601e0 100644 (file)
--- a/drivers/usb/gadget/f_fs.c
+++ b/drivers/usb/gadget/f_fs.c
@@ -712,7 +712,7 @@ static long ffs_ep0_ioctl(struct file *file, unsigned code, unsigned long value)
        if (code == FUNCTIONFS_INTERFACE_REVMAP) {
                struct ffs_function *func = ffs->func;
                ret = func ? ffs_func_revmap_intf(func, value) : -ENODEV;
-       } else if (gadget->ops->ioctl) {
+       } else if (gadget && gadget->ops->ioctl) {
                ret = gadget->ops->ioctl(gadget, code, value);
        } else {
                ret = -ENOTTY;