diff options
| author | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-01-21 17:26:42 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-04-17 08:37:45 +0200 |
| commit | ad2548c9462f1aa41ddb8b7f61afeb418e64cec7 (patch) | |
| tree | 8ec0ef9b04b7f953c15cd4d2f7ddfae955c2a9ea /drivers/tty/tty_ldisc.c | |
| parent | 429977fd9f7153607230a6040ee12510a525e930 (diff) | |
tty: ldisc: add sysctl to prevent autoloading of ldiscs
commit 7c0cca7c847e6e019d67b7d793efbbe3b947d004 upstream.
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>
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty/tty_ldisc.c')
| -rw-r--r-- | drivers/tty/tty_ldisc.c | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c index ca656ef8de64..01fcdc7ff077 100644 --- a/drivers/tty/tty_ldisc.c +++ b/drivers/tty/tty_ldisc.c @@ -155,6 +155,13 @@ static void put_ldops(struct tty_ldisc_ops *ldops) * 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; @@ -169,6 +176,8 @@ static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) */ 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)) @@ -841,3 +850,41 @@ void tty_ldisc_deinit(struct tty_struct *tty) 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); +} |