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Message-ID: <20240223214003.17369-4-kuniyu@amazon.com>
Date: Fri, 23 Feb 2024 13:39:52 -0800
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
<pabeni@...hat.com>
CC: Kuniyuki Iwashima <kuniyu@...zon.com>, Kuniyuki Iwashima
<kuni1840@...il.com>, <netdev@...r.kernel.org>
Subject: [PATCH v3 net-next 03/14] af_unix: Link struct unix_edge when queuing skb.
Just before queuing skb with inflight fds, we call scm_stat_add(),
which is a good place to set up the preallocated struct unix_vertex
and struct unix_edge in UNIXCB(skb).fp.
Then, we call unix_add_edges() and construct the directed graph
as follows:
1. Set the inflight socket's unix_sock to unix_edge.predecessor.
2. Set the receiver's unix_sock to unix_edge.successor.
3. Set the preallocated vertex to inflight socket's unix_sock.vertex.
4. Link inflight socket's unix_vertex.entry to unix_unvisited_vertices.
5. Link unix_edge.vertex_entry to the inflight socket's unix_vertex.edges.
Let's say we pass the fd of AF_UNIX socket A to B and the fd of B
to C. The graph looks like this:
+-------------------------+
| unix_unvisited_vertices | <-------------------------.
+-------------------------+ |
+ |
| +--------------+ +--------------+ | +--------------+
| | unix_sock A | <---. .---> | unix_sock B | <-|-. .---> | unix_sock C |
| +--------------+ | | +--------------+ | | | +--------------+
| .-+ | vertex | | | .-+ | vertex | | | | | vertex |
| | +--------------+ | | | +--------------+ | | | +--------------+
| | | | | | | |
| | +--------------+ | | | +--------------+ | | |
| '-> | unix_vertex | | | '-> | unix_vertex | | | |
| +--------------+ | | +--------------+ | | |
`---> | entry | +---------> | entry | +-' | |
|--------------| | | |--------------| | |
| edges | <-. | | | edges | <-. | |
+--------------+ | | | +--------------+ | | |
| | | | | |
.----------------------' | | .----------------------' | |
| | | | | |
| +--------------+ | | | +--------------+ | |
| | unix_edge | | | | | unix_edge | | |
| +--------------+ | | | +--------------+ | |
`-> | vertex_entry | | | `-> | vertex_entry | | |
|--------------| | | |--------------| | |
| predecessor | +---' | | predecessor | +---' |
|--------------| | |--------------| |
| successor | +-----' | successor | +-----'
+--------------+ +--------------+
Henceforth, we denote such a graph as A -> B (-> C).
Now, we can express all inflight fd graphs that do not contain
embryo sockets. We will support the particular case later.
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
include/net/af_unix.h | 2 +
include/net/scm.h | 1 +
net/core/scm.c | 2 +
net/unix/af_unix.c | 8 +++-
net/unix/garbage.c | 94 ++++++++++++++++++++++++++++++++++++++++++-
5 files changed, 104 insertions(+), 3 deletions(-)
diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index 55c4abc26a71..f31ad1166346 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -22,6 +22,8 @@ extern unsigned int unix_tot_inflight;
void unix_inflight(struct user_struct *user, struct file *fp);
void unix_notinflight(struct user_struct *user, struct file *fp);
+void unix_add_edges(struct scm_fp_list *fpl, struct unix_sock *receiver);
+void unix_del_edges(struct scm_fp_list *fpl);
int unix_prepare_fpl(struct scm_fp_list *fpl);
void unix_destroy_fpl(struct scm_fp_list *fpl);
void unix_gc(void);
diff --git a/include/net/scm.h b/include/net/scm.h
index 5f5154e5096d..bbc5527809d1 100644
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -32,6 +32,7 @@ struct scm_fp_list {
short count_unix;
short max;
#ifdef CONFIG_UNIX
+ bool inflight;
struct list_head vertices;
struct unix_edge *edges;
#endif
diff --git a/net/core/scm.c b/net/core/scm.c
index 1bcc8a2d65e3..5763f3320358 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -90,6 +90,7 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
fpl->max = SCM_MAX_FD;
fpl->user = NULL;
#if IS_ENABLED(CONFIG_UNIX)
+ fpl->inflight = false;
fpl->edges = NULL;
INIT_LIST_HEAD(&fpl->vertices);
#endif
@@ -384,6 +385,7 @@ struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
new_fpl->max = new_fpl->count;
new_fpl->user = get_uid(fpl->user);
#if IS_ENABLED(CONFIG_UNIX)
+ new_fpl->inflight = false;
new_fpl->edges = NULL;
INIT_LIST_HEAD(&new_fpl->vertices);
#endif
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index a3b25d311560..24adbc4d5188 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1943,8 +1943,10 @@ static void scm_stat_add(struct sock *sk, struct sk_buff *skb)
struct scm_fp_list *fp = UNIXCB(skb).fp;
struct unix_sock *u = unix_sk(sk);
- if (unlikely(fp && fp->count))
+ if (unlikely(fp && fp->count)) {
atomic_add(fp->count, &u->scm_stat.nr_fds);
+ unix_add_edges(fp, u);
+ }
}
static void scm_stat_del(struct sock *sk, struct sk_buff *skb)
@@ -1952,8 +1954,10 @@ static void scm_stat_del(struct sock *sk, struct sk_buff *skb)
struct scm_fp_list *fp = UNIXCB(skb).fp;
struct unix_sock *u = unix_sk(sk);
- if (unlikely(fp && fp->count))
+ if (unlikely(fp && fp->count)) {
atomic_sub(fp->count, &u->scm_stat.nr_fds);
+ unix_del_edges(fp);
+ }
}
/*
diff --git a/net/unix/garbage.c b/net/unix/garbage.c
index f31917683288..96d0b1db3638 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -101,6 +101,42 @@ struct unix_sock *unix_get_socket(struct file *filp)
return NULL;
}
+static LIST_HEAD(unix_unvisited_vertices);
+
+static void unix_add_edge(struct scm_fp_list *fpl, struct unix_edge *edge)
+{
+ struct unix_vertex *vertex = edge->predecessor->vertex;
+
+ if (!vertex) {
+ vertex = list_first_entry(&fpl->vertices, typeof(*vertex), entry);
+ vertex->out_degree = 0;
+ INIT_LIST_HEAD(&vertex->edges);
+
+ list_move_tail(&vertex->entry, &unix_unvisited_vertices);
+
+ edge->predecessor->vertex = vertex;
+ }
+
+ vertex->out_degree++;
+
+ list_add_tail(&edge->vertex_entry, &vertex->edges);
+}
+
+static void unix_del_edge(struct scm_fp_list *fpl, struct unix_edge *edge)
+{
+ struct unix_vertex *vertex = edge->predecessor->vertex;
+
+ list_del(&edge->vertex_entry);
+
+ vertex->out_degree--;
+
+ if (!vertex->out_degree) {
+ edge->predecessor->vertex = NULL;
+
+ list_move_tail(&vertex->entry, &fpl->vertices);
+ }
+}
+
static void unix_free_vertices(struct scm_fp_list *fpl)
{
struct unix_vertex *vertex, *next_vertex;
@@ -111,6 +147,60 @@ static void unix_free_vertices(struct scm_fp_list *fpl)
}
}
+DEFINE_SPINLOCK(unix_gc_lock);
+
+void unix_add_edges(struct scm_fp_list *fpl, struct unix_sock *receiver)
+{
+ int i = 0, j = 0;
+
+ spin_lock(&unix_gc_lock);
+
+ if (!fpl->count_unix)
+ goto out;
+
+ do {
+ struct unix_sock *inflight = unix_get_socket(fpl->fp[j++]);
+ struct unix_edge *edge;
+
+ if (!inflight)
+ continue;
+
+ edge = fpl->edges + i++;
+ edge->predecessor = inflight;
+ edge->successor = receiver;
+
+ unix_add_edge(fpl, edge);
+ } while (i < fpl->count_unix);
+
+out:
+ spin_unlock(&unix_gc_lock);
+
+ fpl->inflight = true;
+
+ unix_free_vertices(fpl);
+}
+
+void unix_del_edges(struct scm_fp_list *fpl)
+{
+ int i = 0;
+
+ spin_lock(&unix_gc_lock);
+
+ if (!fpl->count_unix)
+ goto out;
+
+ do {
+ struct unix_edge *edge = fpl->edges + i++;
+
+ unix_del_edge(fpl, edge);
+ } while (i < fpl->count_unix);
+
+out:
+ spin_unlock(&unix_gc_lock);
+
+ fpl->inflight = false;
+}
+
int unix_prepare_fpl(struct scm_fp_list *fpl)
{
struct unix_vertex *vertex;
@@ -141,11 +231,13 @@ int unix_prepare_fpl(struct scm_fp_list *fpl)
void unix_destroy_fpl(struct scm_fp_list *fpl)
{
+ if (fpl->inflight)
+ unix_del_edges(fpl);
+
kvfree(fpl->edges);
unix_free_vertices(fpl);
}
-DEFINE_SPINLOCK(unix_gc_lock);
unsigned int unix_tot_inflight;
static LIST_HEAD(gc_candidates);
static LIST_HEAD(gc_inflight_list);
--
2.30.2
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