Hi Samuel, On Wed, Nov 04, 2020 at 09:13:23PM +0100, Samuel Thibault wrote: > Hello, > > Matthias Reichl, le mer. 04 nov. 2020 15:57:37 +0100, a ecrit: > > I initially noticed this oops on x86_64 running kernel 5.4.59 when > > I accidentally mistyped "ttyS0" as "ttyS9": > > > > modprobe speakup_dummy dev=ttyS9 > > > [ 49.978481] tty_init_dev: ttyS driver does not set tty->port. This would crash the kernel. Fix the driver! > > This looks like only a warning, did it actually crash? Yes, scroll down a bit, the null pointer oops followed almost immediately after that [ 49.979043] BUG: kernel NULL pointer dereference, address: 0000000000000090 > > the missing tty->port is quite fatal. > > It is fatal for module insertion yes (EINVAL) but IIRC that should be > getting handled properly, making modprobe return the error? When I did that on my desktop the tty system was pretty screwed. Mouse still worked in X but no keyboard input possible. > > It looks like spk_ttyio or tty_dev_name_to_number() / tty_kopen() > > should perform some additional validation, > > spk_ttyio_initialise_ldisc only has a dev_t so can't do much beyond > calling tty_kopen. > > tty_kopen is getting the index from the tty_lookup_driver call (actually > get_tty_driver which uses p->minor_start and p->num) and passes it to > tty_driver_lookup_tty. Perhaps in addition of p->num the driver should > have another field to set, that tty_init_dev could use to reject with > ENODEV indexes beyond what the driver actually provides? It might be a bit more involved than a simple max port check, think about hotplug (I have 16C950 ExpressCard devices I occansionally use on one of my laptops) so there may be holes in the allocation numbers. Not sure how/where to best solve this. > > I couldn't make the kernel warn/crash yet by specifying non-existent > > ttyUSB ports yet though. > > That's probably because in the ttyUSB case the device allocation is > dynamic and made exactly according to the number of actual devices, > while for ttyS* there is a large overcommit of minor values. Yes, that sounds reasonable (haven't looked at ttyUSB details, only checked serial core devices yet). so long, Hias
