On Thu, Dec 30, 2021 at 01:11:32PM +0800, Hangyu Hua wrote:
> dev->config and dev->hs_config and dev->dev need to be cleaned if
> dev_config fails to avoid UAF.
>
> Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
You must not do this. I never sent you an Acked-by for this patch; you
shouldn't claim that I did.
> Signed-off-by: Hangyu Hua <hbh25y@xxxxxxxxx>
> ---
> drivers/usb/gadget/legacy/inode.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
> index eaad03c0252f..d2e88f3b9131 100644
> --- a/drivers/usb/gadget/legacy/inode.c
> +++ b/drivers/usb/gadget/legacy/inode.c
> @@ -1847,7 +1847,7 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
> total = le16_to_cpu(dev->hs_config->wTotalLength);
> if (!is_valid_config(dev->hs_config, total) ||
> total > length - USB_DT_DEVICE_SIZE)
> - goto fail;
> + goto fail1;
> kbuf += total;
> length -= total;
> } else {
> @@ -1858,12 +1858,12 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
>
> /* device descriptor (tweaked for paranoia) */
> if (length != USB_DT_DEVICE_SIZE)
> - goto fail;
> + goto fail1;
> dev->dev = (void *)kbuf;
> if (dev->dev->bLength != USB_DT_DEVICE_SIZE
> || dev->dev->bDescriptorType != USB_DT_DEVICE
> || dev->dev->bNumConfigurations != 1)
> - goto fail;
> + goto fail2;
> dev->dev->bcdUSB = cpu_to_le16 (0x0200);
>
> /* triggers gadgetfs_bind(); then we can enumerate. */
> @@ -1875,6 +1875,9 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
>
> value = usb_gadget_probe_driver(&gadgetfs_driver);
> if (value != 0) {
> + dev->dev = NULL;
> + dev->hs_config = NULL;
> + dev->config = NULL;
> kfree (dev->buf);
> dev->buf = NULL;
Why not just grep the lock and goto fail?
> } else {
> @@ -1892,7 +1895,12 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
> }
> return value;
>
> +fail2:
> + dev->dev = NULL;
> +fail1:
> + dev->hs_config = NULL;
It is not necessary to have all these different statement labels. You
can simply have "fail:" clear all three pointers.
> fail:
> + dev->config = NULL;
> spin_unlock_irq (&dev->lock);
> pr_debug ("%s: %s fail %zd, %p\n", shortname, __func__, value, dev);
> kfree (dev->buf);
Alan Stern
