Hi Greg, Thanks for the reply--what you said makes sense. If we find a case where this happens in a normal execution, we will file another bug. Thanks! Anthony On Tue, Jun 23, 2020 at 7:51 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Tue, Jun 23, 2020 at 05:27:33AM -0400, Anthony Canino wrote: > > Hi all, > > > > I hope this is the right place to ask about a potential bug in the TTY > > that I may have found in the TTY layer in the linux kernel. I have > > failed a bug report > > (https://bugzilla.kernel.org/show_bug.cgi?id=208293) but wanted to > > email the list for the TTY layer directly. In summary, in the con_init > > function of drivers/tty/vt/vt.c, I think this code is possibly buggy > > is kzalloc fails to allocate: > > > > 3391 for (currcons = 0; currcons < MIN_NR_CONSOLES; currcons++) { > > 3392 vc_cons[currcons].d = vc = kzalloc(sizeof(struct vc_data), > > GFP_NOWAIT); > > 3393 INIT_WORK(&vc_cons[currcons].SAK_work, vc_SAK); > > 3394 tty_port_init(&vc->port); > > 3395 visual_init(vc, currcons, 1); > > 3396 vc->vc_screenbuf = kzalloc(vc->vc_screenbuf_size, GFP_NOWAIT); > > 3397 vc_init(vc, vc->vc_rows, vc->vc_cols, > > 3398 currcons || !vc->vc_sw->con_save_screen); > > 3399 } > > 3400 currcons = fg_console = 0; > > 3401 master_display_fg = vc = vc_cons[currcons].d; > > 3402 set_origin(vc); > > > > If kzalloc returns null on 3396, I think during set_origin(vc) it is > > possible vc_screenbuf will be dereferenced. I'd be happy to discuss > > further if needed. > > Yes, horrible and bad things will happen if kzalloc fails at that point > in time. > > Luckily, it is impossible for that to happen, so we really do not need > to worry about it at all. This comes up every other year or so, and the > gyrations that people have gone through to try to fix this up, for > something that is impossible to ever hit, always end up breaking the > codebase or doing other horrible things. > > In short, don't worry about it, unless you can show me how that can ever > happen in a normal (i.e. not instrumented) system? > > thanks, > > greg k-h -- Anthony
