Messages in this thread Patch in this message | | | Date | Wed, 23 Sep 2020 13:39:14 +0200 | From | Pavel Machek <> | Subject | fbcon scrollback broken was Re: Linux 5.9-rc6 |
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Hi!
> The one thing that does show up in the diffstat is the softscroll > removal (both fbcon and vgacon), and there are people who want to save > that, but we'll see if some maintainer steps up. I'm not willing to > resurrect it in the broken form it was in, so I doubt that will happen > in 5.9, but we'll see what happens.
Could you... like try not to make the job harder by merging miriad of "let's kill the documentation" patches?
I needed the feature twice already this month, once during fsck, and then five minutes ago, when oops scrolled by me during system shutdown. Unfortunately, shift-pageup was not available to take a look what is going on there.
Unfortunately, Greg backported your "fix" to all the stable releases, so resulting damage will not be easy to repair.
For the record, making the security problem unexploitable should be as simple as patch below.
Unfortunately, Linus' changelog does not exactly tell me what all the known problems are. Willy Tarreau pointed me to https://www.openwall.com/lists/oss-security/2020/09/15/2 , which has some information, but all I can reproduce are transient screen artefacts. If someone has more detailed information, that would be helpful.
Best regards, Pavel
diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index 19cd4a4b1939..cb2d3e7eeac8 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -3211,6 +3212,9 @@ int tioclinux(struct tty_struct *tty, unsigned long arg) ret = fg_console; break; case TIOCL_SCROLLCONSOLE: + ret = -EPERM; + break; + if (get_user(lines, (s32 __user *)(p+4))) { ret = -EFAULT; } else { -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html [unhandled content-type:application/pgp-signature] | |