[PATCH 4.14 20/42] usb: gadget: f_hid: fixed NULL pointer dereference

Greg Kroah-Hartman
2021-08-13T15:13:02Z

From: Phil Elwell <phil@raspberrypi.com>

commit 2867652e4766360adf14dfda3832455e04964f2a upstream.

Disconnecting and reconnecting the USB cable can lead to crashes
and a variety of kernel log spam.

The problem was found and reproduced on the Raspberry Pi [1]
and the original fix was created in Raspberry's own fork [2].

Link: https://github.com/raspberrypi/linux/issues/3870 [1]
Link: https://github.com/raspberrypi/linux/commit/a6e47d5f4efbd2ea6a0b6565cd2f9b7bb217ded5 [2]
Signed-off-by: Maxim Devaev <mdevaev@gmail.com>
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210723155928.210019-1-mdevaev@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/usb/gadget/function/f_hid.c | 26 ++++++++++++++++++++------
1 file changed, 20 insertions(+), 6 deletions(-)

--- a/drivers/usb/gadget/function/f_hid.c
+++ b/drivers/usb/gadget/function/f_hid.c
@@ -349,6 +349,11 @@ static ssize_t f_hidg_write(struct file

spin_lock_irqsave(&hidg->write_spinlock, flags);

+ if (!hidg->req) {
+ spin_unlock_irqrestore(&hidg->write_spinlock, flags);
+ return -ESHUTDOWN;
+ }
+
#define WRITE_COND (!hidg->write_pending)
try_again:
/* write queue */
@@ -369,8 +374,14 @@ try_again:
count = min_t(unsigned, count, hidg->report_length);

spin_unlock_irqrestore(&hidg->write_spinlock, flags);
- status = copy_from_user(req->buf, buffer, count);

+ if (!req) {
+ ERROR(hidg->func.config->cdev, "hidg->req is NULL\n");
+ status = -ESHUTDOWN;
+ goto release_write_pending;
+ }
+
+ status = copy_from_user(req->buf, buffer, count);
if (status != 0) {
ERROR(hidg->func.config->cdev,
"copy_from_user error\n");
@@ -398,14 +409,17 @@ try_again:

spin_unlock_irqrestore(&hidg->write_spinlock, flags);

+ if (!hidg->in_ep->enabled) {
+ ERROR(hidg->func.config->cdev, "in_ep is disabled\n");
+ status = -ESHUTDOWN;
+ goto release_write_pending;
+ }
+
status = usb_ep_queue(hidg->in_ep, req, GFP_ATOMIC);
- if (status < 0) {
- ERROR(hidg->func.config->cdev,
- "usb_ep_queue error on int endpoint %zd\n", status);
+ if (status < 0)
goto release_write_pending;
- } else {
+ else
status = count;
- }

return status;