[PATCH] usb: gadget: udc: Add null pointer check for udc in gadget_match_driver

[Selvarasu Ganesan <selvarasu.g@samsung.com>]

This commit adds a null pointer check for udc in gadget_match_driver to
prevent the below potential dangling pointer access. The issue arises
due to continuous USB role switch and simultaneous UDC write operations
performed by init.rc from user space through configfs.  In these
scenarios, there was a possibility of usb_udc_release being done before
gadget_match_driver.

[27635.233849]  BUG: KASAN: invalid-access in gadget_match_driver+0x40/0x94
[27635.233871]  Read of size 8 at addr d7ffff8837ead080 by task init/1
[27635.233881]  Pointer tag: [d7], memory tag: [fe]
[27635.233888]
[27635.233917]  Call trace:
[27635.233923]   dump_backtrace+0xec/0x10c
[27635.233935]   show_stack+0x18/0x24
[27635.233944]   dump_stack_lvl+0x50/0x6c
[27635.233958]   print_report+0x150/0x6b4
[27635.233977]   kasan_report+0xe8/0x148
[27635.233985]   __hwasan_load8_noabort+0x88/0x98
[27635.233995]   gadget_match_driver+0x40/0x94
[27635.234005]   __driver_attach+0x60/0x304
[27635.234018]   bus_for_each_dev+0x154/0x1b4
[27635.234027]   driver_attach+0x34/0x48
[27635.234036]   bus_add_driver+0x1ec/0x310
[27635.234045]   driver_register+0xc8/0x1b4
[27635.234055]   usb_gadget_register_driver_owner+0x7c/0x140
[27635.234066]   gadget_dev_desc_UDC_store+0x148/0x19c
[27635.234075]   configfs_write_iter+0x180/0x1e0
[27635.234087]   vfs_write+0x298/0x3e4
[27635.234105]   ksys_write+0x88/0x100
[27635.234115]   __arm64_sys_write+0x44/0x5c
[27635.234126]   invoke_syscall+0x6c/0x17c
[27635.234143]   el0_svc_common+0xf8/0x138
[27635.234154]   do_el0_svc+0x30/0x40
[27635.234164]   el0_svc+0x38/0x68
[27635.234174]   el0t_64_sync_handler+0x68/0xbc
[27635.234184]   el0t_64_sync+0x19c/0x1a0

Fixes: fc274c1e9973 ("USB: gadget: Add a new bus for gadgets")
Cc: stable <stable@kernel.org>
Signed-off-by: Selvarasu Ganesan <selvarasu.g@samsung.com>
---
 drivers/usb/gadget/udc/core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index cf6478f97f4a..77dc0f28ff01 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -1338,6 +1338,7 @@ static void usb_udc_release(struct device *dev)
 	udc = container_of(dev, struct usb_udc, dev);
 	dev_dbg(dev, "releasing '%s'\n", dev_name(dev));
 	kfree(udc);
+	udc = NULL;
 }
 
 static const struct attribute_group *usb_udc_attr_groups[];
@@ -1574,7 +1575,7 @@ static int gadget_match_driver(struct device *dev, const struct device_driver *d
 			struct usb_gadget_driver, driver);
 
 	/* If the driver specifies a udc_name, it must match the UDC's name */
-	if (driver->udc_name &&
+	if (driver->udc_name && udc &&
 			strcmp(driver->udc_name, dev_name(&udc->dev)) != 0)
 		return 0;
 
-- 
2.17.1