buf->length is first copied in from user space and security-checked. The second copy issued by copy_from_user copies it again. The data in user space may have been modified by malicious users. filter_callback() further uses the potentially modified data. The fix avoids the double-fetch that overwrites buf->length.
Signed-off-by: Kangjie Lu <[email protected]> --- drivers/platform/x86/wmi.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c index bea35be68706..93cab9a70ad7 100644 --- a/drivers/platform/x86/wmi.c +++ b/drivers/platform/x86/wmi.c @@ -850,7 +850,8 @@ static long wmi_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) buf->length, wblock->req_buf_size); /* copy the structure from userspace */ - if (copy_from_user(buf, input, wblock->req_buf_size)) { + if (copy_from_user(buf->data, input->data, + wblock->req_buf_size - sizeof(buf->length))) { dev_dbg(&wblock->dev.dev, "Copy %llu from user failed\n", wblock->req_buf_size); ret = -EFAULT; -- 2.17.2 (Apple Git-113)
