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wayland-server: fix socket ownership race condition

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Always unlink() the lock file before closing the file
descriptor for it. Otherwise, there is a race like this:

Process A closes fd, releasing the lock
Process B opens the same file, taking the lock
Process A unlinks the lock file
Process C opens the same file, which now no longer exists,
and takes the lock on the newly created lock file

Process B and C both 'own' the same display socket.

unlink()ing while holding the lock is effectively a better
way to release the lock atomically.
This commit is contained in:
Dylan Noblesmith 2012-06-30 19:50:09 +00:00
parent 9475257459
commit 30ff420ca9
1 changed files with 10 additions and 10 deletions
Download patch file Download diff file Expand all files Collapse all files

20
src/wayland-server.c
View file

@ -1001,10 +1001,10 @@ wl_display_destroy(struct wl_display *display)
wl_list_for_each_safe(s, next, &display->socket_list, link) { wl_list_for_each_safe(s, next, &display->socket_list, link) {
wl_event_source_remove(s->source); wl_event_source_remove(s->source);
close(s->fd);
unlink(s->addr.sun_path); unlink(s->addr.sun_path);
close(s->fd_lock); close(s->fd);
unlink(s->lock_addr); unlink(s->lock_addr);
close(s->fd_lock);
free(s); free(s);
} }
wl_event_loop_destroy(display->loop); wl_event_loop_destroy(display->loop);
@ -1196,18 +1196,18 @@ wl_display_add_socket(struct wl_display *display, const char *name)
size = offsetof (struct sockaddr_un, sun_path) + name_size; size = offsetof (struct sockaddr_un, sun_path) + name_size;
if (bind(s->fd, (struct sockaddr *) &s->addr, size) < 0) { if (bind(s->fd, (struct sockaddr *) &s->addr, size) < 0) {
close(s->fd_lock);
unlink(s->lock_addr);
close(s->fd); close(s->fd);
unlink(s->lock_addr);
close(s->fd_lock);
free(s); free(s);
return -1; return -1;
} }
if (listen(s->fd, 1) < 0) { if (listen(s->fd, 1) < 0) {
close(s->fd_lock);
unlink(s->lock_addr);
close(s->fd);
unlink(s->addr.sun_path); unlink(s->addr.sun_path);
close(s->fd);
unlink(s->lock_addr);
close(s->fd_lock);
free(s); free(s);
return -1; return -1;
} }
@ -1216,10 +1216,10 @@ wl_display_add_socket(struct wl_display *display, const char *name)
WL_EVENT_READABLE, WL_EVENT_READABLE,
socket_data, display); socket_data, display);
if (s->source == NULL) { if (s->source == NULL) {
close(s->fd_lock);
unlink(s->lock_addr);
close(s->fd);
unlink(s->addr.sun_path); unlink(s->addr.sun_path);
close(s->fd);
unlink(s->lock_addr);
close(s->fd_lock);
free(s); free(s);
return -1; return -1;
} }