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HID: roccat: Fix use-after-free in roccat_read()
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>
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