From d6934fa92ba225b941b2085fd480eefab9eca53c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?G=C3=BCnther=20Noack?= Date: Fri, 10 Jan 2025 14:21:22 +0000 Subject: [PATCH] tty: Permit some TIOCL_SETSEL modes without CAP_SYS_ADMIN MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit BugLink: https://bugs.launchpad.net/bugs/2114239 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 Link: https://lore.kernel.org/r/ee3ec63269b43b34e1c90dd8c9743bf8@finder.org Fixes: 8d1b43f6a6df ("tty: Restrict access to TIOCLINUX' copy-and-paste subcommands") Signed-off-by: Günther Noack Reviewed-by: Kees Cook Link: https://lore.kernel.org/r/20250110142122.1013222-1-gnoack@google.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Noah Wager Signed-off-by: Mehmet Basaran --- drivers/tty/vt/selection.c | 14 ++++++++++++++ drivers/tty/vt/vt.c | 2 -- 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/drivers/tty/vt/selection.c b/drivers/tty/vt/selection.c index e172ede235a0..a2afc3d35fd0 100644 --- a/drivers/tty/vt/selection.c +++ b/drivers/tty/vt/selection.c @@ -183,6 +183,20 @@ 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); } diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index 9bdbf2a4684f..3bec3381accf 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -3157,8 +3157,6 @@ 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))