Re: [PATCH RFC v2 0/6] staging: r8188eu: avoid uninit value bugs

Pavel Skripkin
2021-08-23T06:44:31Z

On 8/23/21 3:12 AM, Phillip Potter wrote:
> On Sun, 22 Aug 2021 at 15:35, Pavel Skripkin <paskripkin@gmail.com> wrote:
>>
>> Hi, Greg, Larry and Phillip!
>>
>> I noticed, that new staging driver was added like 3 weeks ago and I decided
>> to look at the code, because drivers in staging directory are always buggy.
>>
>> The first thing I noticed is *no one* was checking read operations result, but
>> it can fail and driver may start writing random stack values into registers. It
>> can cause driver misbehavior or device misbehavior.
>>
>> To avoid this type of bugs, i've changed rtw_read* API. Now all rtw_read
>> funtions return an error, when something went wrong with usb transfer.
>>
>> It helps callers to break/return earlier and don't write random values to
>> registers or to rely on random values.
>>
>> Why is this pacth series RFC?
>> 1. I don't have this device and I cannot test these changes.
>> 2. I don't know how to handle errors in each particular case. For now, function
>> just returns or returns an error. That's all. I hope, driver maintainers will
>> help with these bits.
>> 3. I guess, I handled not all uninit value bugs here. I hope, I fixed
>> at least half of them
>>
>>
>> v1 -> v2:
>> 1. Make rtw_read*() return an error instead of initializing pointer to error
>> 2. Split one huge patch to smaller ones for each rtw_read{8,16,32} function
>> changes
>> 3. Add new macro for printing register values (It helps to not copy-paste error
>> handling)
>> 4. Removed {read,write}_macreg (Suggested by Phillip)
>> 5. Rebased on top of staging-next
>> 6. Cleaned checkpatch errors and warnings
>>
>> Only build-tested, since I don't have device with r8118eu chip
>>
>> Pavel Skripkin (6):
>> staging: r8188eu: remove {read,write}_macreg
>> staging: r8188eu: add helper macro for printing registers
>> staging: r8188eu: add error handling of rtw_read8
>> staging: r8188eu: add error handling of rtw_read16
>> staging: r8188eu: add error handling of rtw_read32
>> staging: r8188eu: make ReadEFuse return an int
>>
>> drivers/staging/r8188eu/core/rtw_debug.c | 79 +++-
>> drivers/staging/r8188eu/core/rtw_efuse.c | 125 +++--
>> drivers/staging/r8188eu/core/rtw_io.c | 27 +-
>> drivers/staging/r8188eu/core/rtw_mp.c | 70 ++-
>> drivers/staging/r8188eu/core/rtw_mp_ioctl.c | 13 +-
>> drivers/staging/r8188eu/core/rtw_pwrctrl.c | 5 +-
>> drivers/staging/r8188eu/core/rtw_sreset.c | 9 +-
>> .../r8188eu/hal/Hal8188ERateAdaptive.c | 8 +-
>> drivers/staging/r8188eu/hal/HalPhyRf_8188e.c | 21 +-
>> drivers/staging/r8188eu/hal/HalPwrSeqCmd.c | 9 +-
>> drivers/staging/r8188eu/hal/hal_com.c | 23 +-
>> drivers/staging/r8188eu/hal/hal_intf.c | 6 +-
>> drivers/staging/r8188eu/hal/odm_interface.c | 12 +-
>> drivers/staging/r8188eu/hal/rtl8188e_cmd.c | 33 +-
>> drivers/staging/r8188eu/hal/rtl8188e_dm.c | 6 +-
>> .../staging/r8188eu/hal/rtl8188e_hal_init.c | 285 +++++++++---
>> drivers/staging/r8188eu/hal/rtl8188e_phycfg.c | 27 +-
>> drivers/staging/r8188eu/hal/rtl8188e_sreset.c | 22 +-
>> drivers/staging/r8188eu/hal/rtl8188eu_led.c | 18 +-
>> drivers/staging/r8188eu/hal/usb_halinit.c | 439 +++++++++++++++---
>> drivers/staging/r8188eu/hal/usb_ops_linux.c | 57 ++-
>> drivers/staging/r8188eu/include/hal_intf.h | 6 +-
>> .../staging/r8188eu/include/odm_interface.h | 6 +-
>> .../staging/r8188eu/include/rtl8188e_hal.h | 2 +-
>> drivers/staging/r8188eu/include/rtw_debug.h | 13 +
>> drivers/staging/r8188eu/include/rtw_efuse.h | 4 +-
>> drivers/staging/r8188eu/include/rtw_io.h | 18 +-
>> drivers/staging/r8188eu/include/rtw_mp.h | 2 -
>> drivers/staging/r8188eu/os_dep/ioctl_linux.c | 179 +++++--
>> drivers/staging/r8188eu/os_dep/usb_intf.c | 3 +-
>> 30 files changed, 1138 insertions(+), 389 deletions(-)
>>
>> --
>> 2.32.0
>>
>
> Dear Pavel,
>
> Thanks for this. I like the code a lot. One thing I am conflicted on
> is the helper macro for the printing of register values though. Whilst
> I'm not necessarily opposed to the concept of the macro itself, I
> don't think it should rely on GlobalDebugLevel for one thing - if we
> are going to control printing of messages at runtime then in my mind
> this should be done via debugfs and pr_debug or similar - an in-kernel
> mechanism rather than something driver-provided. Also, the example you
> give of:
>
> u32 tmp;
> if (!rtw_read(&tmp))
> DBG("reg = %d\n", tmp);
>
> Doesn't seem overly unclear to me if DBG was a pr_debug or similar,
> but I get what you're saying about repetition. This is just a small
> thing though, would be interested to see what others think. Many
> thanks.
>

Btw, did you have a chance to test these changes? My r8188eu device
_should_ come in few days, so I am not able to test it right now :)

With regards,
Pavel Skripkin