mherrb/seatd
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seat: Avoid holding a tty fd

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The kernel Secure Attention Key killer, triggered by SysRq+k, kills all
processes that hold an fd referencing the tty.

To avoid its attention, we stop storing the fd for the currently active
VT in seat state. This has the added benefit of simplifying state a bit.
This commit is contained in:
Kenny Levinsen 2021-04-23 00:17:19 +02:00
parent 15b0972bd3
commit df3f307b8e
2 changed files with 16 additions and 36 deletions
Download patch file Download diff file Expand all files Collapse all files

1
include/seat.h
View file

@ -33,7 +33,6 @@ struct seat {
struct client *next_client; struct client *next_client;
bool vt_bound; bool vt_bound;
int cur_ttyfd;
int cur_vt; int cur_vt;
int session_cnt; int session_cnt;
}; };

51
seatd/seat.c
View file

@ -19,7 +19,7 @@
#include "terminal.h" #include "terminal.h"
static int seat_close_client(struct client *client); static int seat_close_client(struct client *client);
static void vt_close(struct seat *seat); static int vt_close(int vt);
struct seat *seat_create(const char *seat_name, bool vt_bound) { struct seat *seat_create(const char *seat_name, bool vt_bound) {
struct seat *seat = calloc(1, sizeof(struct seat)); struct seat *seat = calloc(1, sizeof(struct seat));
@ -30,7 +30,6 @@ struct seat *seat_create(const char *seat_name, bool vt_bound) {
seat->vt_bound = vt_bound; seat->vt_bound = vt_bound;
seat->seat_name = strdup(seat_name); seat->seat_name = strdup(seat_name);
seat->cur_vt = 0; seat->cur_vt = 0;
seat->cur_ttyfd = -1;
if (seat->seat_name == NULL) { if (seat->seat_name == NULL) {
free(seat); free(seat);
return NULL; return NULL;
@ -50,7 +49,6 @@ void seat_destroy(struct seat *seat) {
assert(client->seat == seat); assert(client->seat == seat);
client_destroy(client); client_destroy(client);
} }
vt_close(seat);
linked_list_remove(&seat->link); linked_list_remove(&seat->link);
free(seat->seat_name); free(seat->seat_name);
free(seat); free(seat);
@ -66,47 +64,30 @@ static void seat_update_vt(struct seat *seat) {
close(tty0fd); close(tty0fd);
} }
static int vt_open(struct seat *seat, int vt) { static int vt_open(int vt) {
assert(vt != -1); assert(vt != -1);
if (seat->cur_ttyfd != -1) { int ttyfd = terminal_open(vt);
terminal_set_process_switching(seat->cur_ttyfd, true); if (ttyfd == -1) {
close(seat->cur_ttyfd);
}
seat->cur_ttyfd = terminal_open(vt);
if (seat->cur_ttyfd == -1) {
log_errorf("Could not open terminal for VT %d: %s", vt, strerror(errno)); log_errorf("Could not open terminal for VT %d: %s", vt, strerror(errno));
return -1; return -1;
} }
terminal_set_process_switching(seat->cur_ttyfd, true); terminal_set_process_switching(ttyfd, true);
terminal_set_keyboard(seat->cur_ttyfd, false); terminal_set_keyboard(ttyfd, false);
terminal_set_graphics(seat->cur_ttyfd, true); terminal_set_graphics(ttyfd, true);
close(ttyfd);
return 0; return 0;
} }
static void vt_close_fd(int fd) { static int vt_close(int vt) {
terminal_set_process_switching(fd, true);
terminal_set_keyboard(fd, true);
terminal_set_graphics(fd, false);
}
static void vt_close(struct seat *seat) {
if (seat->cur_ttyfd == -1) {
return;
}
vt_close_fd(seat->cur_ttyfd);
close(seat->cur_ttyfd);
seat->cur_ttyfd = -1;
}
static int vt_close_num(int vt) {
int ttyfd = terminal_open(vt); int ttyfd = terminal_open(vt);
if (ttyfd == -1) { if (ttyfd == -1) {
log_errorf("Could not open terminal to clean up VT %d: %s", vt, strerror(errno)); log_errorf("Could not open terminal to clean up VT %d: %s", vt, strerror(errno));
return -1; return -1;
} }
vt_close_fd(ttyfd); terminal_set_process_switching(ttyfd, true);
terminal_set_keyboard(ttyfd, true);
terminal_set_graphics(ttyfd, false);
close(ttyfd); close(ttyfd);
return 0; return 0;
} }
@ -452,7 +433,7 @@ int seat_open_client(struct seat *seat, struct client *client) {
return -1; return -1;
} }
if (seat->vt_bound && vt_open(seat, client->session) == -1) { if (seat->vt_bound && vt_open(client->session) == -1) {
log_error("Could not open VT for client"); log_error("Could not open VT for client");
goto error; goto error;
} }
@ -477,7 +458,7 @@ int seat_open_client(struct seat *seat, struct client *client) {
error: error:
if (seat->vt_bound) { if (seat->vt_bound) {
vt_close(seat); vt_close(seat->cur_vt);
} }
return -1; return -1;
} }
@ -506,12 +487,12 @@ static int seat_close_client(struct client *client) {
// This client was current, but there were no clients // This client was current, but there were no clients
// waiting to take this VT, so clean it up. // waiting to take this VT, so clean it up.
log_debug("Closing active VT"); log_debug("Closing active VT");
vt_close(seat); vt_close(seat->cur_vt);
} else if (!was_current && client->state != CLIENT_CLOSED) { } else if (!was_current && client->state != CLIENT_CLOSED) {
// This client was not current, but as the client was // This client was not current, but as the client was
// running, we need to clean up the VT. // running, we need to clean up the VT.
log_debug("Closing inactive VT"); log_debug("Closing inactive VT");
vt_close_num(client->session); vt_close(client->session);
} }
} }