@@ -33,6 +33,7 @@ struct scm_fp_list {
short max;
#ifdef CONFIG_UNIX
bool inflight;
+ bool dead;
struct list_head vertices;
struct unix_edge *edges;
#endif
@@ -91,6 +91,7 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
fpl->user = NULL;
#if IS_ENABLED(CONFIG_UNIX)
fpl->inflight = false;
+ fpl->dead = false;
fpl->edges = NULL;
INIT_LIST_HEAD(&fpl->vertices);
#endif
@@ -158,13 +158,11 @@ static void unix_add_edge(struct scm_fp_list *fpl, struct unix_edge *edge)
unix_update_graph(unix_edge_successor(edge));
}
-static bool gc_in_progress;
-
static void unix_del_edge(struct scm_fp_list *fpl, struct unix_edge *edge)
{
struct unix_vertex *vertex = edge->predecessor->vertex;
- if (!gc_in_progress)
+ if (!fpl->dead)
unix_update_graph(unix_edge_successor(edge));
list_del(&edge->vertex_entry);
@@ -240,7 +238,7 @@ void unix_del_edges(struct scm_fp_list *fpl)
unix_del_edge(fpl, edge);
} while (i < fpl->count_unix);
- if (!gc_in_progress) {
+ if (!fpl->dead) {
receiver = fpl->edges[0].successor;
receiver->scm_stat.nr_unix_fds -= fpl->count_unix;
}
@@ -559,9 +557,12 @@ static void unix_walk_scc_fast(struct sk_buff_head *hitlist)
list_replace_init(&unix_visited_vertices, &unix_unvisited_vertices);
}
+static bool gc_in_progress;
+
static void __unix_gc(struct work_struct *work)
{
struct sk_buff_head hitlist;
+ struct sk_buff *skb;
spin_lock(&unix_gc_lock);
@@ -579,6 +580,11 @@ static void __unix_gc(struct work_struct *work)
spin_unlock(&unix_gc_lock);
+ skb_queue_walk(&hitlist, skb) {
+ if (UNIXCB(skb).fp)
+ UNIXCB(skb).fp->dead = true;
+ }
+
__skb_queue_purge(&hitlist);
skip_gc:
WRITE_ONCE(gc_in_progress, false);
Commit 1af2dface5d2 ("af_unix: Don't access successor in unix_del_edges() during GC.") fixed use-after-free by avoid accessing edge->successor while GC is in progress. However, there could be a small race window where another process could call unix_del_edges() while gc_in_progress is true and __skb_queue_purge() is on the way. So, we cannot rely on gc_in_progress and need another marker per struct scm_fp_list which indicates if the skb is garbage-collected. This patch adds dead flag in struct scm_fp_list and set it true before calling __skb_queue_purge() in __unix_gc(). Fixes: 1af2dface5d2 ("af_unix: Don't access successor in unix_del_edges() during GC.") Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> --- include/net/scm.h | 1 + net/core/scm.c | 1 + net/unix/garbage.c | 14 ++++++++++---- 3 files changed, 12 insertions(+), 4 deletions(-)