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.
v2:
1. break one patch up into two separate patches.
2. use "fail:" to clear all members.
v3:
fix a mistake in [PATCH v3 2/2]
Hangyu Hua (2):
usb: gadget: don't release an existing dev->buf
usb: gadget: clear related members when goto fail
drivers/usb/gadget/legacy/inode.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
--
2.25.1
dev->buf does not need to be released if it already exists before
executing dev_config.
Acked-by: Alan Stern <[email protected]>
Signed-off-by: Hangyu Hua <[email protected]>
---
drivers/usb/gadget/legacy/inode.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/gadget/legacy/inode.c b/drivers/usb/gadget/legacy/inode.c
index 3b58f4fc0a80..eaad03c0252f 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;
--
2.25.1
dev->config and dev->hs_config and dev->dev need to be cleaned if
dev_config fails to avoid UAF.
Acked-by: Alan Stern <[email protected]>
Signed-off-by: Hangyu Hua <[email protected]>
---
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;
} 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;
fail:
+ dev->config = NULL;
spin_unlock_irq (&dev->lock);
pr_debug ("%s: %s fail %zd, %p\n", shortname, __func__, value, dev);
kfree (dev->buf);
--
2.25.1
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 <[email protected]>
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 <[email protected]>
> ---
> 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
On Thu, Dec 30, 2021 at 02:46:00PM -0500, Alan Stern wrote:
> 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.
> > @@ -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?
Wrong word: I meant to write "grab", not "grep".
Alan Stern
On 2021/12/31 上午3:46, Alan Stern wrote:
> You must not do this. I never sent you an Acked-by for this patch; you
> shouldn't claim that I did.
I am sorry about this. I should read the linux kernel community rules
more carefully.
>> 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?
You are right. I will modify my patch later.
>> } 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
>
I don't think so. It is not necessary to clean all three pointers if
some of them aren't kbuf. I think it may be better to keep their own
pointers.
Thanks. Happy new year.
On Fri, Dec 31, 2021 at 10:31:51AM +0800, Hangyu Hua wrote:
> On 2021/12/31 上午3:46, Alan Stern wrote:
> >> @@ -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.
> I don't think so. It is not necessary to clean all three pointers if
> some of them aren't kbuf. I think it may be better to keep their own
> pointers.
If the pointers aren't set to a region inside kbuf then they are
meaningless. There is no reason to keep the old values. It is better
to avoid multiple unnecessary statement labels.
Alan Stern
I get that. I will fix and resubmit my patch.
Thanks again.
On 2021/12/31 下午11:57, Alan Stern wrote:
> On Fri, Dec 31, 2021 at 10:31:51AM +0800, Hangyu Hua wrote:
>> On 2021/12/31 上午3:46, Alan Stern wrote:
>
>>>> @@ -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.
>
>> I don't think so. It is not necessary to clean all three pointers if
>> some of them aren't kbuf. I think it may be better to keep their own
>> pointers.
>
> If the pointers aren't set to a region inside kbuf then they are
> meaningless. There is no reason to keep the old values. It is better
> to avoid multiple unnecessary statement labels.
>
> Alan Stern
>