usb: gadget: function: fix dangling pnp_string in f_printer.c

stable inclusion
from stable-v5.10.150
commit 7efdd91d54cbf42a8079ebbdc677a16984b2f9b7
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6D0XA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7efdd91d54cbf42a8079ebbdc677a16984b2f9b7

--------------------------------

[ Upstream commit 24b7ba2f ]

When opts->pnp_string is changed with configfs, new memory is allocated for
the string. It does not, however, update dev->pnp_string, even though the
memory is freed. When rquesting the string, the host then gets old or
corrupted data rather than the new string. The ieee 1284 id string should
be allowed to change while the device is connected.

The bug was introduced in commit fdc01cc2 ("usb: gadget: printer:
Remove pnp_string static buffer"), which changed opts->pnp_string from a
char[] to a char*.
This patch changes dev->pnp_string from a char* to a char** pointing to
opts->pnp_string.

Fixes: fdc01cc2 ("usb: gadget: printer: Remove pnp_string static buffer")
Signed-off-by: NAlbert Briscoe <albertsbriscoe@gmail.com>
Link: https://lore.kernel.org/r/20220911223753.20417-1-albertsbriscoe@gmail.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NJialin Zhang <zhangjialin11@huawei.com>

drivers/usb/gadget/function/f_printer.c

@@ -87,7 +87,7 @@ struct printer_dev {
 	u8			printer_cdev_open;
 	wait_queue_head_t	wait;
 	unsigned		q_len;
-	char			*pnp_string;	/* We don't own memory! */
+	char			**pnp_string;	/* We don't own memory! */
 	struct usb_function	function;
 };
 
@@ -999,16 +999,16 @@ static int printer_func_setup(struct usb_function *f,
 			if ((wIndex>>8) != dev->interface)
 				break;
 
-			if (!dev->pnp_string) {
+			if (!*dev->pnp_string) {
 				value = 0;
 				break;
 			}
-			value = strlen(dev->pnp_string);
+			value = strlen(*dev->pnp_string);
 			buf[0] = (value >> 8) & 0xFF;
 			buf[1] = value & 0xFF;
-			memcpy(buf + 2, dev->pnp_string, value);
+			memcpy(buf + 2, *dev->pnp_string, value);
 			DBG(dev, "1284 PNP String: %x %s\n", value,
-			    dev->pnp_string);
+			    *dev->pnp_string);
 			break;
 
 		case GET_PORT_STATUS: /* Get Port Status */
@@ -1471,7 +1471,7 @@ static struct usb_function *gprinter_alloc(struct usb_function_instance *fi)
 	kref_init(&dev->kref);
 	++opts->refcnt;
 	dev->minor = opts->minor;
-	dev->pnp_string = opts->pnp_string;
+	dev->pnp_string = &opts->pnp_string;
 	dev->q_len = opts->q_len;
 	mutex_unlock(&opts->lock);