Re: [PATCH v3 2/2] usb: gadget: clear related members when goto fail
From: Alan Stern <stern@rowland.harvard.edu>
Date: 2021-12-30 19:46:07
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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@rowland.harvard.edu>
You must not do this. I never sent you an Acked-by for this patch; you shouldn't claim that I did.
quoted hunk ↗ jump to hunk
Signed-off-by: Hangyu Hua <redacted> --- 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?
quoted hunk ↗ jump to hunk
} 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