Re: UBSAN: Undefined behaviour in drivers/tty/vt/keyboard.c

[Greg KH]

On Sun, Mar 22, 2020 at 11:34:01PM -0400, Kyungtae Kim wrote:
> We report a bug (in linux-5.5.11) found by FuzzUSB (modified version
> of syzkaller)
> 
> Seems the variable "npadch" has a very large value (i.e., 333333333)
> as a result of multiple executions of the function "k_ascii" (keyboard.c:888)
> while the variable "base" has 10.
> So their multiplication at line 888 in "k_ascii" will become
> larger than the max of type int, causing such an integer overflow.
> 
> I believe this can be solved by checking for overflow ahead of operations
> e.g., using check_mul_overflow().
> 
> kernel config: https://kt0755.github.io/etc/config_v5.5.11

Great, can you send a patch for this?

thanks,

greg k-h