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kmscon: add --session-max parameter

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This parameter allows to limit the maximum number of sessions to a sane
limit. Otherwise, a user could DOS a systemd by opening as many session as
they want.
This can be set to 0 to drop that limit, however, this is not recommended.
Instead, if you want an ability to add more sessions than that limit, you
should implement a flag to register_session() that overwrites the limit.
This can then be used by a safe way to register new sessions.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
This commit is contained in:
David Herrmann 2012-10-18 13:28:10 +02:00
parent ebce60a86a
commit 18b0011d55
3 changed files with 17 additions and 0 deletions
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4
src/kmscon_conf.c
View File

@ -120,6 +120,9 @@ static void print_help()
"\t --grab-terminal-new <grab> [<Ctrl><Alt>Return]\n"
"\t Create new terminal session\n"
"\n"
"Session Options:\n"
"\t --session-max <max> [50] Maximum number of sessions\n"
"\n"
"Font Options:\n"
"\t --font-engine <engine> [pango]\n"
"\t Font engine\n"
@ -298,6 +301,7 @@ struct conf_option options[] = {
CONF_OPTION_UINT(0, "font-size", NULL, &kmscon_conf.font_size, 12),
CONF_OPTION_STRING(0, "font-name", NULL, &kmscon_conf.font_name, "monospace"),
CONF_OPTION_UINT(0, "font-dpi", NULL, &kmscon_conf.font_ppi, 96),
CONF_OPTION_UINT(0, "session-max", NULL, &kmscon_conf.session_max, 50),
CONF_OPTION_STRING_LIST(0, "seats", aftercheck_seats, &kmscon_conf.seats, def_seats),
};

3
src/kmscon_conf.h
View File

@ -94,6 +94,9 @@ struct kmscon_conf_t {
char **seats;
bool all_seats;
/* sessions */
unsigned int session_max;
/* font engine */
char *font_engine;
/* font size */

10
src/kmscon_seat.c
View File

@ -73,6 +73,7 @@ struct kmscon_seat {
struct uterm_vt *vt;
struct shl_dlist displays;
size_t session_count;
struct shl_dlist sessions;
struct kmscon_session *cur_sess;
struct kmscon_session *dummy;
@ -560,6 +561,13 @@ int kmscon_seat_register_session(struct kmscon_seat *seat,
if (!seat || !out)
return -EINVAL;
if (kmscon_conf.session_max &&
seat->session_count >= kmscon_conf.session_max) {
log_warning("maximum number of sessions reached (%d), dropping new session",
kmscon_conf.session_max);
return -EOVERFLOW;
}
sess = malloc(sizeof(*sess));
if (!sess) {
log_error("cannot allocate memory for new session on seat %s",
@ -576,6 +584,7 @@ int kmscon_seat_register_session(struct kmscon_seat *seat,
sess->data = data;
shl_dlist_link_tail(&seat->sessions, &sess->list);
++seat->session_count;
*out = sess;
shl_dlist_for_each(iter, &seat->displays) {
@ -612,6 +621,7 @@ void kmscon_session_unregister(struct kmscon_session *sess)
session_deactivate(sess);
shl_dlist_unlink(&sess->list);
--sess->seat->session_count;
sess->seat = NULL;
session_call(sess, KMSCON_SESSION_UNREGISTER, NULL);
}