From: Hyunwoo Kim imv4bel@gmail.com
[ Upstream commit cacdb14b1c8d3804a3a7d31773bc7569837b71a4 ]
roccat_report_event() is responsible for registering roccat-related reports in struct roccat_device.
int roccat_report_event(int minor, u8 const *data) { struct roccat_device *device; struct roccat_reader *reader; struct roccat_report *report; uint8_t *new_value;
device = devices[minor];
new_value = kmemdup(data, device->report_size, GFP_ATOMIC); if (!new_value) return -ENOMEM;
report = &device->cbuf[device->cbuf_end];
/* passing NULL is safe */ kfree(report->value); ...
The registered report is stored in the struct roccat_device member "struct roccat_report cbuf[ROCCAT_CBUF_SIZE];". If more reports are received than the "ROCCAT_CBUF_SIZE" value, kfree() the saved report from cbuf[0] and allocates a new reprot. Since there is no lock when this kfree() is performed, kfree() can be performed even while reading the saved report.
static ssize_t roccat_read(struct file *file, char __user *buffer, size_t count, loff_t *ppos) { struct roccat_reader *reader = file->private_data; struct roccat_device *device = reader->device; struct roccat_report *report; ssize_t retval = 0, len; DECLARE_WAITQUEUE(wait, current);
mutex_lock(&device->cbuf_lock);
...
report = &device->cbuf[reader->cbuf_start]; /* * If report is larger than requested amount of data, rest of report * is lost! */ len = device->report_size > count ? count : device->report_size;
if (copy_to_user(buffer, report->value, len)) { retval = -EFAULT; goto exit_unlock; } ...
The roccat_read() function receives the device->cbuf report and delivers it to the user through copy_to_user(). If the N+ROCCAT_CBUF_SIZE th report is received while copying of the Nth report->value is in progress, the pointer that copy_to_user() is working on is kfree()ed and UAF read may occur. (race condition)
Since the device node of this driver does not set separate permissions, this is not a security vulnerability, but because it is used for requesting screen display of profile or dpi settings, a user using the roccat device can apply udev to this device node or There is a possibility to use it by giving.
Signed-off-by: Hyunwoo Kim imv4bel@gmail.com Signed-off-by: Jiri Kosina jkosina@suse.cz Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/hid/hid-roccat.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/drivers/hid/hid-roccat.c b/drivers/hid/hid-roccat.c index 26373b82fe81..6da80e442fdd 100644 --- a/drivers/hid/hid-roccat.c +++ b/drivers/hid/hid-roccat.c @@ -257,6 +257,8 @@ int roccat_report_event(int minor, u8 const *data) if (!new_value) return -ENOMEM;
+ mutex_lock(&device->cbuf_lock); + report = &device->cbuf[device->cbuf_end];
/* passing NULL is safe */ @@ -276,6 +278,8 @@ int roccat_report_event(int minor, u8 const *data) reader->cbuf_start = (reader->cbuf_start + 1) % ROCCAT_CBUF_SIZE; }
+ mutex_unlock(&device->cbuf_lock); + wake_up_interruptible(&device->wait); return 0; }