[0/4] USB: sisusbvga: cleaning up char buffers to u8 buffer

Message

Changming June 26, 2020, 7:34 p.m. UTC

The purpose of this patch series is to prevent
undefined behavior caused by arithemetic operations on
the content of the char buffer.This is achieved through
converting all char buffers to u8 when there is 
no need for the content to be negative value(which is the 
case for all touched buffer in this patch series).

Converting these char buffers to u8 buffers will make 
certain types of UB from producing undefined result to 
well-defined intended (modular) result, and will not 
introduce any unintended side effect.

As an example, changing the local char buf[4] in sisusb_write_mem_bulk
to u8 fixes an UB: since buf is filled with data from user space,
thus can be negative. Left-shifting this negative value produces
undefined result, this can be fixed by changing it from char 
to u8.

This however doesn't apply to ioctl interfaces functions, since the 
types for buffer of ioctl-like functions need to be 
char* instead of u8* for compatibility reason.
In these cases, the buffer declared as char* will be force cast
to u8* when being used.


Changming Liu (4):
  USB: sisusbvga: change sisusb_write_mem_bulk
  USB: sisusbvga: change the buffers of sisusb from char to u8
  USB: sisusbvga: change userbuffer for sisusb_recv_bulk_msg to u8
  USB: sisusbvga: change sisusb_read_mem_bulk

 drivers/usb/misc/sisusbvga/sisusb.c | 34 +++++++++++++++++-----------------
 drivers/usb/misc/sisusbvga/sisusb.h |  4 ++--
 2 files changed, 19 insertions(+), 19 deletions(-)