Messages in this thread Patch in this message |  | | | Date | Sat, 30 Jun 2001 23:10:40 +0200 | | Subject | PATCH: drivers/char/vt.c allows virtually locking up nonnetworked machine | | From | Rudolf Polzer <> |
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There is a problem concerning chvt. A normal user can run a
bash$ while [ 1 ]; do chvt 11; done
which cannot be killed using the console (only remotely, virtually never on a nonnetworked multiuser machine). So I changed the kernel source code so that only the superuser may change terminals.
Since renaming/deleting chvt is no solution (chvt is a simple ioctl call), it seems to be the simplest way to prevent this. Console switching using Ctrl-Alt-Fkey still works, as well as X, so probably there are no implications in most cases.
But, since this may be too restrictive for some applications, I would recommend making this a configuration option. Unfortunately I do not know how to do this :(
--- drivers/char/vt.c.orig Mon Jun 25 09:00:28 2001 +++ drivers/char/vt.c Sat Jun 30 23:02:56 2001 @@ -435,10 +435,16 @@ /* * To have permissions to do most of the vt ioctls, we either have - * to be the owner of the tty, or super-user. + * to be the owner of the tty, or super-user. Only the superuser + * if you want added security. + */ + + /* + * disable a security hole, therefore the first check is commented + * out! */ perm = 0; - if (current->tty == tty || suser()) + if (/* current->tty == tty || */ suser()) perm = 1; kbd = kbd_table + console; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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