On Thu, 2020-10-29 at 01:55 +0800, Macpaul Lin wrote:

From: Eddie Hung eddie.hung@mediatek.com

There is a use-after-free issue, if access udc_name in function gadget_dev_desc_UDC_store after another context free udc_name in function unregister_gadget.

Context 1: gadget_dev_desc_UDC_store()->unregister_gadget()-> free udc_name->set udc_name to NULL

Context 2: gadget_dev_desc_UDC_show()-> access udc_name

Call trace: dump_backtrace+0x0/0x340 show_stack+0x14/0x1c dump_stack+0xe4/0x134 print_address_description+0x78/0x478 __kasan_report+0x270/0x2ec kasan_report+0x10/0x18 __asan_report_load1_noabort+0x18/0x20 string+0xf4/0x138 vsnprintf+0x428/0x14d0 sprintf+0xe4/0x12c gadget_dev_desc_UDC_show+0x54/0x64 configfs_read_file+0x210/0x3a0 __vfs_read+0xf0/0x49c vfs_read+0x130/0x2b4 SyS_read+0x114/0x208 el0_svc_naked+0x34/0x38

Add mutex_lock to protect this kind of scenario.

Signed-off-by: Eddie Hung eddie.hung@mediatek.com Signed-off-by: Macpaul Lin macpaul.lin@mediatek.com Reviewed-by: Peter Chen peter.chen@nxp.com Cc: stable@vger.kernel.org

---

Changes for v2:

• Fix typo %s/contex/context, Thanks Peter.

drivers/usb/gadget/configfs.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c index 56051bb..d9743f4 100644 --- a/drivers/usb/gadget/configfs.c +++ b/drivers/usb/gadget/configfs.c @@ -221,9 +221,16 @@ static ssize_t gadget_dev_desc_bcdUSB_store(struct config_item *item, static ssize_t gadget_dev_desc_UDC_show(struct config_item *item, char *page) {

• char *udc_name = to_gadget_info(item)->composite.gadget_driver.udc_name;

• struct gadget_info *gi = to_gadget_info(item);
• char *udc_name;
• int ret;
• mutex_lock(&gi->lock);
• udc_name = gi->composite.gadget_driver.udc_name;
• ret = sprintf(page, "%s\n", udc_name ?: "");
• mutex_unlock(&gi->lock);

• return sprintf(page, "%s\n", udc_name ?: "");

• return ret;

} static int unregister_gadget(struct gadget_info *gi)

Sorry, it looks like still a base64 encoded mail. I'll feedback to our IT department again. Please ignore this mail.

Thanks Macpaul Lin