[PATCH v1 net] af_unix: Convert unsigned long to u64 for GC.

[Kuniyuki Iwashima <kuniyu@google.com>]

Lim Chanyoun reported that unix_vertex_max_scc_index could
wrap around on 32-bit kernels, which confuses GC into purging
a live socket receive queue.

I apparently designed GC with u64 in mind to avoid wraparound. [0]

Let's make it true on 32-bit kernels.

Note that unix_vertex.{out_degree,index} are converted for
consistency; they are bounded by the number of allocated
objects and do not exceed UINT_MAX on 32-bit kernels.

Fixes: 4090fa373f0e ("af_unix: Replace garbage collection algorithm.")
Link: https://lore.kernel.org/netdev/20240228030508.31297-1-kuniyu@amazon.com/ #[0]
Reported-by: Lim Chanyoun <onleaf322@gmail.com>
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
 net/unix/garbage.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/net/unix/garbage.c b/net/unix/garbage.c
index da774f56ca64..a0b515354e8b 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -78,9 +78,9 @@ struct unix_vertex {
 	struct list_head edges;
 	struct list_head entry;
 	struct list_head scc_entry;
-	unsigned long out_degree;
-	unsigned long index;
-	unsigned long scc_index;
+	u64 out_degree;
+	u64 index;
+	u64 scc_index;
 };
 
 struct unix_edge {
@@ -148,8 +148,8 @@ enum unix_vertex_index {
 	UNIX_VERTEX_INDEX_START,
 };
 
-static unsigned long unix_vertex_unvisited_index = UNIX_VERTEX_INDEX_MARK1;
-static unsigned long unix_vertex_max_scc_index = UNIX_VERTEX_INDEX_START;
+static u64 unix_vertex_unvisited_index = UNIX_VERTEX_INDEX_MARK1;
+static u64 unix_vertex_max_scc_index = UNIX_VERTEX_INDEX_START;
 
 static void unix_add_edge(struct scm_fp_list *fpl, struct unix_edge *edge)
 {
@@ -372,7 +372,7 @@ static bool unix_vertex_dead(struct unix_vertex *vertex)
 }
 
 static LIST_HEAD(unix_visited_vertices);
-static unsigned long unix_vertex_grouped_index = UNIX_VERTEX_INDEX_MARK2;
+static u64 unix_vertex_grouped_index = UNIX_VERTEX_INDEX_MARK2;
 
 static bool unix_scc_dead(struct list_head *scc)
 {
@@ -450,14 +450,14 @@ static bool unix_scc_cyclic(struct list_head *scc)
 	return false;
 }
 
-static unsigned long __unix_walk_scc(struct unix_vertex *vertex,
-				     unsigned long *last_index,
-				     struct sk_buff_head *hitlist)
+static u64 __unix_walk_scc(struct unix_vertex *vertex,
+			   u64 *last_index,
+			   struct sk_buff_head *hitlist)
 {
-	unsigned long cyclic_sccs = 0;
 	LIST_HEAD(vertex_stack);
 	struct unix_edge *edge;
 	LIST_HEAD(edge_stack);
+	u64 cyclic_sccs = 0;
 
 next_vertex:
 	/* Push vertex to vertex_stack and mark it as on-stack
@@ -553,12 +553,12 @@ static unsigned long __unix_walk_scc(struct unix_vertex *vertex,
 	return cyclic_sccs;
 }
 
-static unsigned long unix_graph_cyclic_sccs;
+static u64 unix_graph_cyclic_sccs;
 
 static void unix_walk_scc(struct sk_buff_head *hitlist)
 {
-	unsigned long last_index = UNIX_VERTEX_INDEX_START;
-	unsigned long cyclic_sccs = 0;
+	u64 last_index = UNIX_VERTEX_INDEX_START;
+	u64 cyclic_sccs = 0;
 
 	unix_vertex_max_scc_index = UNIX_VERTEX_INDEX_START;
 
@@ -582,7 +582,7 @@ static void unix_walk_scc(struct sk_buff_head *hitlist)
 
 static void unix_walk_scc_fast(struct sk_buff_head *hitlist)
 {
-	unsigned long cyclic_sccs = unix_graph_cyclic_sccs;
+	u64 cyclic_sccs = unix_graph_cyclic_sccs;
 
 	while (!list_empty(&unix_unvisited_vertices)) {
 		struct unix_vertex *vertex;
-- 
2.56.0.385.gac671c819a-goog