On June 17, 2025 3:10:52 PM PDT, "Pádraig Brady" <p...@draigbrady.com> wrote: >On 17/06/2025 20:07, H. Peter Anvin wrote: >> On June 17, 2025 5:58:48 AM PDT, "Pádraig Brady" <p...@draigbrady.com> wrote: >>> We'll need to adjust tests a bit. >>> Currently we check that `stty ispeed 420` fails, >>> though I'm guessing that this may now succeed with glibc >= 2.42? >>> Do you have any ideas on how to test this?Note we can distinguish the >>> TERMIOS_SPEED_T_SANE valuethough `stty ispeed 420` returning "invalid >>> ispeed". >>> >>> cheers, >>> Pádraig >> >> Yes, that will succeed with glibc 2.42+, as will split speed. >> >> The most straightforward way to test would of course be to have a test >> program that does an explicit tcgetattr, but otherwise I think the answer is >> you should either get back what you set or get an error. > >Given that the system can now potentially accept any value, >I think what I'll do is create a follow up patch to LD_PRELOAD a cfsetispeed >that always returns -1, to verify we error for that. >> If you think it would be useful, it would not be hard to add an option to >> list the enumerated speeds or show the range of speeds that can be >> represented in a speed_t. >That would probably be overkill, given potentially anything is accepted. > >Talking about range though, >I'm thinking we should explicitly disallow negative values? >Currently (on 64 bit) the following is equivalent to 9600 which is just >confusing I think: > > stty ispeed '-18446744073709542016' > >Note the current code clamps overflow values to ULONG_MAX, >passing that down for the lower layers to validate. >That's probably OK to leave as is. > >I'll make that negative check adjustment also before pushing unless I hear >otherwise. > >cheers, >Pádraig >
It's a bit odd that it is accepted if speed_t is unsigned int, though. I did put in a check for that, but perhaps I got the casting rules wrong. One more thing: *if* the macro __MAX_BAUD is defined, it normally should contain the maximum permitted value of speed_t. I just don't know how universal that is...
