From: Günther Noack <gnoack@xxxxxxxxxx> commit 2f83e38a095f8bf7c6029883d894668b03b9bd93 upstream. 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@xxxxxxxxxx> Link: https://lore.kernel.org/r/ee3ec63269b43b34e1c90dd8c9743bf8@xxxxxxxxxx Fixes: 8d1b43f6a6df ("tty: Restrict access to TIOCLINUX' copy-and-paste subcommands") Signed-off-by: Günther Noack <gnoack@xxxxxxxxxx> Reviewed-by: Kees Cook <kees@xxxxxxxxxx> Link: https://lore.kernel.org/r/20250110142122.1013222-1-gnoack@xxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/tty/vt/selection.c | 14 ++++++++++++++ drivers/tty/vt/vt.c | 2 -- 2 files changed, 14 insertions(+), 2 deletions(-) --- a/drivers/tty/vt/selection.c +++ b/drivers/tty/vt/selection.c @@ -192,6 +192,20 @@ int set_selection_user(const struct tioc 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); } --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -3345,8 +3345,6 @@ int tioclinux(struct tty_struct *tty, un 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)) Patches currently in stable-queue which might be from gnoack@xxxxxxxxxx are queue-6.12/tty-permit-some-tiocl_setsel-modes-without-cap_sys_admin.patch
