6.6-stable review patch. If anyone has any objections, please let me know.
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From: Kuniyuki Iwashima kuniyu@amazon.com
commit 7172dc93d621d5dc302d007e95ddd1311ec64283 upstream.
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 need another marker for 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().
Fixes: 1af2dface5d2 ("af_unix: Don't access successor in unix_del_edges() during GC.") Signed-off-by: Kuniyuki Iwashima kuniyu@amazon.com Acked-by: Paolo Abeni pabeni@redhat.com Link: https://lore.kernel.org/r/20240508171150.50601-1-kuniyu@amazon.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Lee Jones lee@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- include/net/scm.h | 1 + net/core/scm.c | 1 + net/unix/garbage.c | 14 ++++++++++---- 3 files changed, 12 insertions(+), 4 deletions(-)
--- a/include/net/scm.h +++ b/include/net/scm.h @@ -32,6 +32,7 @@ struct scm_fp_list { short max; #ifdef CONFIG_UNIX bool inflight; + bool dead; struct list_head vertices; struct unix_edge *edges; #endif --- a/net/core/scm.c +++ b/net/core/scm.c @@ -91,6 +91,7 @@ static int scm_fp_copy(struct cmsghdr *c fpl->user = NULL; #if IS_ENABLED(CONFIG_UNIX) fpl->inflight = false; + fpl->dead = false; fpl->edges = NULL; INIT_LIST_HEAD(&fpl->vertices); #endif --- a/net/unix/garbage.c +++ b/net/unix/garbage.c @@ -158,13 +158,11 @@ static void unix_add_edge(struct scm_fp_ 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 * 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 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
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);