On 8/24/21 2:33 AM, Phillip Potter wrote:
On Sun, 22 Aug 2021 at 15:36, Pavel Skripkin <paskripkin@xxxxxxxxx> wrote:-static u32 usb_read32(struct intf_hdl *pintfhdl, u32 addr) +static int usb_read32(struct intf_hdl *pintfhdl, u32 addr, u32 *data) { u8 requesttype; u16 wvalue; u16 len; - __le32 data; + int res; + __le32 tmp; + + if (WARN_ON(unlikely(!data))) + return -EINVAL; requesttype = 0x01;/* read_in */ wvalue = (u16)(addr & 0x0000ffff); len = 4; - usbctrl_vendorreq(pintfhdl, wvalue, &data, len, requesttype); + res = usbctrl_vendorreq(pintfhdl, wvalue, &data, len, requesttype); + if (res < 0) { + dev_err(dvobj_to_dev(pintfhdl->pintf_dev), "Failed to read 32 bytes: %d\n", res); + } else { + /* Noone cares about positive return value */ + *data = le32_to_cpu(tmp); + res = 0; + } - return le32_to_cpu(data); + return res; }Dear Pavel, OK, found the issue with decoded stack trace after reviewing this usb_read32 function. Your line: res = usbctrl_vendorreq(pintfhdl, wvalue, &data, len, requesttype); should read: res = usbctrl_vendorreq(pintfhdl, wvalue, &tmp, len, requesttype); With this change, the driver runs fine with no crashes/oopses. I will explain the issue but you can probably see already, so I hope I'm not coming across as patronising, just trying to be helpful :-) Essentially, you are taking the address of the data function parameter on this line with &data, a pointer to u32, which is giving you a pointer to a pointer to u32 (u32 **) for this function parameter variable. When passed to usbctrl_vendorreq, it is being passed to memcpy inside this function as a void *, meaning that memcpy subsequently overwrites the value of the memory address inside data to point to a different location, which is problem when it is later deferenced at: *data = le32_to_cpu(tmp); causing the OOPS
The most strange thing is why gcc didn't complain about different pointer types... I think, that gcc must complain about this type of not explicit casts, because 99% it's a bug.
Again big thanks for analysis :) With regards, Pavel Skripkin
