Messages in this thread | | | Subject | Re: [PATCH RFC v2 5/6] staging: r8188eu: add error handling of rtw_read32 | From | Pavel Skripkin <> | Date | Tue, 24 Aug 2021 09:53:37 +0300 |
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On 8/24/21 2:33 AM, Phillip Potter wrote: > On Sun, 22 Aug 2021 at 15:36, Pavel Skripkin <paskripkin@gmail.com> 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
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