diff options
Diffstat (limited to '0009-tty-ldisc-add-sysctl-to-prevent-autoloading-of-ldisc.patch')
| -rw-r--r-- | 0009-tty-ldisc-add-sysctl-to-prevent-autoloading-of-ldisc.patch | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/0009-tty-ldisc-add-sysctl-to-prevent-autoloading-of-ldisc.patch b/0009-tty-ldisc-add-sysctl-to-prevent-autoloading-of-ldisc.patch new file mode 100644 index 00000000000000..e5039346d971e6 --- /dev/null +++ b/0009-tty-ldisc-add-sysctl-to-prevent-autoloading-of-ldisc.patch @@ -0,0 +1,137 @@ +From 813613139b98f5c811441d1292ffd1760b55defa Mon Sep 17 00:00:00 2001 +From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> +Date: Mon, 21 Jan 2019 09:45:58 +0100 +Subject: [PATCH 09/11] tty: ldisc: add sysctl to prevent autoloading of ldiscs + +By default, the kernel will automatically load the module of any line +dicipline that is asked for. As this sometimes isn't the safest thing +to do, provide a sysctl to disable this feature. + +By default, we set this to 'y' as that is the historical way that Linux +has worked, and we do not want to break working systems. But in the +future, perhaps this can default to 'n' to prevent this functionality. + +Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> +--- + drivers/tty/Kconfig | 24 ++++++++++++++++++++++++ + drivers/tty/tty_io.c | 3 +++ + drivers/tty/tty_ldisc.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++ + 3 files changed, 74 insertions(+) + +--- a/drivers/tty/Kconfig ++++ b/drivers/tty/Kconfig +@@ -441,4 +441,28 @@ config VCC + depends on SUN_LDOMS + help + Support for Sun logical domain consoles. ++ ++config LDISC_AUTOLOAD ++ bool "Automatically load TTY Line Disciplines" ++ default y ++ help ++ Historically the kernel has always automatically loaded any ++ line discipline that is in a kernel module when a user asks ++ for it to be loaded with the TIOCSETD ioctl, or through other ++ means. This is not always the best thing to do on systems ++ where you know you will not be using some of the more ++ "ancient" line disciplines, so prevent the kernel from doing ++ this unless the request is coming from a process with the ++ CAP_SYS_MODULE permissions. ++ ++ Say 'Y' here if you trust your userspace users to do the right ++ thing, or if you have only provided the line disciplines that ++ you know you will be using, or if you wish to continue to use ++ the traditional method of on-demand loading of these modules ++ by any user. ++ ++ This functionality can be changed at runtime with the ++ dev.tty.ldisc_autoload sysctl, this configuration option will ++ only set the default value of this functionality. ++ + endif # TTY +--- a/drivers/tty/tty_io.c ++++ b/drivers/tty/tty_io.c +@@ -513,6 +513,8 @@ static const struct file_operations hung + static DEFINE_SPINLOCK(redirect_lock); + static struct file *redirect; + ++extern void tty_sysctl_init(void); ++ + /** + * tty_wakeup - request more data + * @tty: terminal +@@ -3483,6 +3485,7 @@ void console_sysfs_notify(void) + */ + int __init tty_init(void) + { ++ tty_sysctl_init(); + cdev_init(&tty_cdev, &tty_fops); + if (cdev_add(&tty_cdev, MKDEV(TTYAUX_MAJOR, 0), 1) || + register_chrdev_region(MKDEV(TTYAUX_MAJOR, 0), 1, "/dev/tty") < 0) +--- a/drivers/tty/tty_ldisc.c ++++ b/drivers/tty/tty_ldisc.c +@@ -156,6 +156,13 @@ static void put_ldops(struct tty_ldisc_o + * takes tty_ldiscs_lock to guard against ldisc races + */ + ++#if defined(CONFIG_LDISC_AUTOLOAD) ++ #define INITIAL_AUTOLOAD_STATE 1 ++#else ++ #define INITIAL_AUTOLOAD_STATE 0 ++#endif ++static int tty_ldisc_autoload = INITIAL_AUTOLOAD_STATE; ++ + static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) + { + struct tty_ldisc *ld; +@@ -170,6 +177,8 @@ static struct tty_ldisc *tty_ldisc_get(s + */ + ldops = get_ldops(disc); + if (IS_ERR(ldops)) { ++ if (!capable(CAP_SYS_MODULE) && !tty_ldisc_autoload) ++ return ERR_PTR(-EPERM); + request_module("tty-ldisc-%d", disc); + ldops = get_ldops(disc); + if (IS_ERR(ldops)) +@@ -845,3 +854,41 @@ void tty_ldisc_deinit(struct tty_struct + tty_ldisc_put(tty->ldisc); + tty->ldisc = NULL; + } ++ ++static int zero; ++static int one = 1; ++static struct ctl_table tty_table[] = { ++ { ++ .procname = "ldisc_autoload", ++ .data = &tty_ldisc_autoload, ++ .maxlen = sizeof(tty_ldisc_autoload), ++ .mode = 0644, ++ .proc_handler = proc_dointvec, ++ .extra1 = &zero, ++ .extra2 = &one, ++ }, ++ { } ++}; ++ ++static struct ctl_table tty_dir_table[] = { ++ { ++ .procname = "tty", ++ .mode = 0555, ++ .child = tty_table, ++ }, ++ { } ++}; ++ ++static struct ctl_table tty_root_table[] = { ++ { ++ .procname = "dev", ++ .mode = 0555, ++ .child = tty_dir_table, ++ }, ++ { } ++}; ++ ++void tty_sysctl_init(void) ++{ ++ register_sysctl_table(tty_root_table); ++} |