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Subject[PATCH] usb: gadget: use after free in dev_config
Date
There are two bugs:
dev->buf does not need to be released if it already exists before
executing dev_config.
dev->config and dev->hs_config and dev->dev need to be cleaned if
dev_config fails to avoid UAF.

Signed-off-by: Hangyu Hua <hbh25y@gmail.com>
---
drivers/usb/gadget/legacy/inode.c | 23 ++++++++++++++++++-----
1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
index 3b58f4fc0a80..2ea02887025b 100644
--- a/drivers/usb/gadget/legacy/inode.c
+++ b/drivers/usb/gadget/legacy/inode.c
@@ -1826,8 +1826,9 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
spin_lock_irq (&dev->lock);
value = -EINVAL;
if (dev->buf) {
+ spin_unlock_irq(&dev->lock);
kfree(kbuf);
- goto fail;
+ return value;
}
dev->buf = kbuf;

@@ -1835,8 +1836,10 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
dev->config = (void *) kbuf;
total = le16_to_cpu(dev->config->wTotalLength);
if (!is_valid_config(dev->config, total) ||
- total > length - USB_DT_DEVICE_SIZE)
+ total > length - USB_DT_DEVICE_SIZE) {
+ dev->config = NULL;
goto fail;
+ }
kbuf += total;
length -= total;

@@ -1845,8 +1848,11 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
dev->hs_config = (void *) kbuf;
total = le16_to_cpu(dev->hs_config->wTotalLength);
if (!is_valid_config(dev->hs_config, total) ||
- total > length - USB_DT_DEVICE_SIZE)
+ total > length - USB_DT_DEVICE_SIZE) {
+ dev->config = NULL;
+ dev->hs_config = NULL;
goto fail;
+ }
kbuf += total;
length -= total;
} else {
@@ -1856,13 +1862,20 @@ dev_config (struct file *fd, const char __user *buf, size_t len, loff_t *ptr)
/* could support multiple configs, using another encoding! */

/* device descriptor (tweaked for paranoia) */
- if (length != USB_DT_DEVICE_SIZE)
+ if (length != USB_DT_DEVICE_SIZE) {
+ dev->config = NULL;
+ dev->hs_config = NULL;
goto fail;
+ }
dev->dev = (void *)kbuf;
if (dev->dev->bLength != USB_DT_DEVICE_SIZE
|| dev->dev->bDescriptorType != USB_DT_DEVICE
- || dev->dev->bNumConfigurations != 1)
+ || dev->dev->bNumConfigurations != 1) {
+ dev->config = NULL;
+ dev->hs_config = NULL;
+ dev->dev = NULL;
goto fail;
+ }
dev->dev->bcdUSB = cpu_to_le16 (0x0200);

/* triggers gadgetfs_bind(); then we can enumerate. */
--
2.25.1
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