Current main event loop (event_loop()) of tgtd has a possibility of
segmentation fault. The problem is caused by the below sequence:
1. Event A, B are ready so epoll_wait(2) returns.
2. The handler of the event A is called. In the event handler, the
event B is deleted with tgt_event_del()
3. event_loop() tries to call the handler of the event B. It causes
segfault because the event struct is already removed and freed.
For avoid this problem, this patch adds a new global variable
event_need_refresh. If the value of this variable is 1, event_loop()
calls epoll_wait(2) again for refreshing ready fd list. This patch
also lets tgt_event_del() to turn on the flag in its tail. With this
modification, the above segfault is avoided.
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@xxxxxxxxxxxxx>
---
usr/tgtd.c | 10 ++++++++++
usr/tgtd.h | 2 ++
2 files changed, 12 insertions(+)
diff --git a/usr/tgtd.c b/usr/tgtd.c
index 09c1442..c758458 100644
--- a/usr/tgtd.c
+++ b/usr/tgtd.c
@@ -215,6 +215,8 @@ static struct event_data *tgt_event_lookup(int fd)
return NULL;
}
+int event_need_refresh;
+
void tgt_event_del(int fd)
{
struct event_data *tev;
@@ -232,6 +234,8 @@ void tgt_event_del(int fd)
list_del(&tev->e_list);
free(tev);
+
+ event_need_refresh = 1;
}
int tgt_event_modify(int fd, int events)
@@ -419,6 +423,7 @@ retry:
sched_remains = tgt_exec_scheduled();
timeout = sched_remains ? 0 : -1;
+refresh:
nevent = epoll_wait(ep_fd, events, ARRAY_SIZE(events), timeout);
if (nevent < 0) {
if (errno != EINTR) {
@@ -429,6 +434,11 @@ retry:
for (i = 0; i < nevent; i++) {
tev = (struct event_data *) events[i].data.ptr;
tev->handler(tev->fd, events[i].events, tev->data);
+
+ if (event_need_refresh) {
+ event_need_refresh = 0;
+ goto refresh;
+ }
}
}
diff --git a/usr/tgtd.h b/usr/tgtd.h
index a708f13..91dd7b4 100644
--- a/usr/tgtd.h
+++ b/usr/tgtd.h
@@ -406,4 +406,6 @@ struct service_action *
find_service_action(struct service_action *service_action,
uint32_t action);
+extern int event_need_refresh;
+
#endif
--
1.7.10.4
--
To unsubscribe from this list: send the line "unsubscribe stgt" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
