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-rw-r--r--net/unix/garbage.c35
1 files changed, 25 insertions, 10 deletions
diff --git a/net/unix/garbage.c b/net/unix/garbage.c
index 027c86e804..2a758531e1 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -166,17 +166,18 @@ static void scan_children(struct sock *x, void (*func)(struct unix_sock *),
static void dec_inflight(struct unix_sock *usk)
{
- atomic_long_dec(&usk->inflight);
+ usk->inflight--;
}
static void inc_inflight(struct unix_sock *usk)
{
- atomic_long_inc(&usk->inflight);
+ usk->inflight++;
}
static void inc_inflight_move_tail(struct unix_sock *u)
{
- atomic_long_inc(&u->inflight);
+ u->inflight++;
+
/* If this still might be part of a cycle, move it to the end
* of the list, so that it's checked even if it was already
* passed over
@@ -234,20 +235,34 @@ void unix_gc(void)
* receive queues. Other, non candidate sockets _can_ be
* added to queue, so we must make sure only to touch
* candidates.
+ *
+ * Embryos, though never candidates themselves, affect which
+ * candidates are reachable by the garbage collector. Before
+ * being added to a listener's queue, an embryo may already
+ * receive data carrying SCM_RIGHTS, potentially making the
+ * passed socket a candidate that is not yet reachable by the
+ * collector. It becomes reachable once the embryo is
+ * enqueued. Therefore, we must ensure that no SCM-laden
+ * embryo appears in a (candidate) listener's queue between
+ * consecutive scan_children() calls.
*/
list_for_each_entry_safe(u, next, &gc_inflight_list, link) {
+ struct sock *sk = &u->sk;
long total_refs;
- long inflight_refs;
- total_refs = file_count(u->sk.sk_socket->file);
- inflight_refs = atomic_long_read(&u->inflight);
+ total_refs = file_count(sk->sk_socket->file);
- BUG_ON(inflight_refs < 1);
- BUG_ON(total_refs < inflight_refs);
- if (total_refs == inflight_refs) {
+ BUG_ON(!u->inflight);
+ BUG_ON(total_refs < u->inflight);
+ if (total_refs == u->inflight) {
list_move_tail(&u->link, &gc_candidates);
__set_bit(UNIX_GC_CANDIDATE, &u->gc_flags);
__set_bit(UNIX_GC_MAYBE_CYCLE, &u->gc_flags);
+
+ if (sk->sk_state == TCP_LISTEN) {
+ unix_state_lock_nested(sk, U_LOCK_GC_LISTENER);
+ unix_state_unlock(sk);
+ }
}
}
@@ -271,7 +286,7 @@ void unix_gc(void)
/* Move cursor to after the current position. */
list_move(&cursor, &u->link);
- if (atomic_long_read(&u->inflight) > 0) {
+ if (u->inflight) {
list_move_tail(&u->link, &not_cycle_list);
__clear_bit(UNIX_GC_MAYBE_CYCLE, &u->gc_flags);
scan_children(&u->sk, inc_inflight_move_tail, NULL);