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8bd29dbe03
In as102_usb driver, the following race condition occurs:
```
CPU0 CPU1
as102_usb_probe()
kzalloc(); // alloc as102_dev_t
....
usb_register_dev();
fd = sys_open("/path/to/dev"); // open as102 fd
....
usb_deregister_dev();
....
kfree(); // free as102_dev_t
....
sys_close(fd);
as102_release() // UAF!!
as102_usb_release()
kfree(); // DFB!!
```
When a USB character device registered with usb_register_dev() is later
unregistered (via usb_deregister_dev() or disconnect), the device node is
removed so new open() calls fail. However, file descriptors that are
already open do not go away immediately: they remain valid until the last
reference is dropped and the driver's .release() is invoked.
In as102, as102_usb_probe() calls usb_register_dev() and then, on an
error path, does usb_deregister_dev() and frees as102_dev_t right away.
If userspace raced a successful open() before the deregistration, that
open FD will later hit as102_release() --> as102_usb_release() and access
or free as102_dev_t again, occur a race to use-after-free and
double-free vuln.
The fix is to never kfree(as102_dev_t) directly once usb_register_dev()
has succeeded. After deregistration, defer freeing memory to .release().
In other words, let release() perform the last kfree when the final open
FD is closed.
Cc: <stable@vger.kernel.org>
Reported-by: syzbot+47321e8fd5a4c84088db@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=47321e8fd5a4c84088db
Fixes:
|
||
|---|---|---|
| .. | ||
| as10x_cmd_cfg.c | ||
| as10x_cmd_stream.c | ||
| as10x_cmd.c | ||
| as10x_cmd.h | ||
| as10x_handle.h | ||
| as102_drv.c | ||
| as102_drv.h | ||
| as102_fw.c | ||
| as102_fw.h | ||
| as102_usb_drv.c | ||
| as102_usb_drv.h | ||
| Kconfig | ||
| Makefile | ||