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

Phillip Potter
2021-08-23T00:12:57Z

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.

Regards,
Phil