Commit 2f83e38a authored by Günther Noack's avatar Günther Noack Committed by Greg Kroah-Hartman
Browse files

tty: Permit some TIOCL_SETSEL modes without CAP_SYS_ADMIN 

With this, processes without CAP_SYS_ADMIN are able to use TIOCLINUX with
subcode TIOCL_SETSEL, in the selection modes TIOCL_SETPOINTER,
TIOCL_SELCLEAR and TIOCL_SELMOUSEREPORT.

TIOCL_SETSEL was previously changed to require CAP_SYS_ADMIN, as this IOCTL
let callers change the selection buffer and could be used to simulate
keypresses.  These three TIOCL_SETSEL selection modes, however, are safe to
use, as they do not modify the selection buffer.

This fixes a mouse support regression that affected Emacs (invisible mouse
cursor).

Cc: stable <stable@kernel.org>
Link: https://lore.kernel.org/r/ee3ec63269b43b34e1c90dd8c9743bf8@finder.org


Fixes: 8d1b43f6 ("tty: Restrict access to TIOCLINUX' copy-and-paste subcommands")
Signed-off-by: default avatarGünther Noack <gnoack@google.com>
Reviewed-by: default avatarKees Cook <kees@kernel.org>
Link: https://lore.kernel.org/r/20250110142122.1013222-1-gnoack@google.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b06f3889

drivers/tty/vt/selection.c

+14 −0
Original line number Diff line number Diff line
@@ -192,6 +192,20 @@ int set_selection_user(const struct tiocl_selection __user *sel, 
	if (copy_from_user(&v, sel, sizeof(*sel)))

		return -EFAULT;



	/*

	 * TIOCL_SELCLEAR, TIOCL_SELPOINTER and TIOCL_SELMOUSEREPORT are OK to

	 * use without CAP_SYS_ADMIN as they do not modify the selection.

	 */

	switch (v.sel_mode) {

	case TIOCL_SELCLEAR:

	case TIOCL_SELPOINTER:

	case TIOCL_SELMOUSEREPORT:

		break;

	default:

		if (!capable(CAP_SYS_ADMIN))

			return -EPERM;

	}



	return set_selection_kernel(&v, tty);

}

drivers/tty/vt/vt.c

+0 −2
Original line number Diff line number Diff line
@@ -3345,8 +3345,6 @@ int tioclinux(struct tty_struct *tty, unsigned long arg) 


	switch (type) {

	case TIOCL_SETSEL:

		if (!capable(CAP_SYS_ADMIN))

			return -EPERM;

		return set_selection_user(param, tty);

	case TIOCL_PASTESEL:

		if (!capable(CAP_SYS_ADMIN))