Re: [Qemu-devel] [PATCH 3/6] gdbstub: Reject invalid RLE repeat counts

[Philippe Mathieu-Daudé]

On 4/18/19 4:53 PM, Markus Armbruster wrote:
> "Debugging with GDB / Appendix E GDB Remote Serial Protocol /
> Overview" specifies "The printable characters '#' and '$' or with a
> numeric value greater than 126 must not be used."  gdb_read_byte()
> only rejects values < 32.  This is wrong.  Impact depends on the caller:
> 
> * gdb_handlesig() passes a char.  Incorrectly accepts '#', '$' and
>   '\127'.
> 
> * gdb_chr_receive() passes an uint8_t.  Additionally accepts
>   characters with the most-significant bit set.
> 
> Correct the validity check to match the specification.
> 
> Signed-off-by: Markus Armbruster <address@hidden>
> ---
>  gdbstub.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/gdbstub.c b/gdbstub.c
> index d54abd17cc..a6dce1b027 100644
> --- a/gdbstub.c
> +++ b/gdbstub.c
> @@ -2064,7 +2064,7 @@ static void gdb_read_byte(GDBState *s, int ch)
>              }
>              break;
>          case RS_GETLINE_RLE:
> -            if (ch < ' ') {

Can you add a comment referring to the ""Debugging with GDB / Appendix E
GDB Remote Serial Protocol / Overview" here?

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

> +            if (ch < ' ' || ch == '#' || ch == '$' || ch > 126) {
>                  /* invalid RLE count encoding */
>                  trace_gdbstub_err_invalid_repeat((uint8_t)ch);
>                  s->state = RS_GETLINE;
>