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Message-ID: <20240216210556.65913-4-kuniyu@amazon.com>
Date: Fri, 16 Feb 2024 13:05:45 -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 v2 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_edge
in UNIXCB(skb).fp->edges.
Then, we call unix_add_edges() and construct the directed graph
as follows:
1. Set the inflight socket's unix_vertex to unix_edge.predecessor
2. Set the receiver's unix_vertex to unix_edge.successor
3. Link unix_edge.entry to the inflight socket's unix_vertex.edges
4. Link inflight socket's unix_vertex.entry to unix_unvisited_vertices.
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 |
| +-------------+ +-------------+ | +-------------+
| | unix_vertex | <----. .----> | unix_vertex | <-|--. .----> | unix_vertex |
| | +-----------+ | | | +-----------+ | | | | +-----------+
`-> | | entry | +------------> | | entry | +-' | | | | entry |
| |-----------| | | | |-----------| | | | |-----------|
| | edges | <-. | | | | edges | <-. | | | | edges |
+-+-----------+ | | | +-+-----------+ | | | +-+-----------+
| | | | | |
.---------------------' | | .---------------------' | |
| | | | | |
| +-------------+ | | | +-------------+ | |
| | unix_edge | | | | | unix_edge | | |
| +-------------+ | | | +-------------+ | |
`-> | entry | | | `-> | 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. The following two patches will support the
particular case.
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 | 55 ++++++++++++++++++++++++++++++++++++++++++-
5 files changed, 65 insertions(+), 3 deletions(-)
diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index cab9dfb666f3..54d62467a70b 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -23,6 +23,8 @@ 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_init_vertex(struct unix_sock *u);
+void unix_add_edges(struct scm_fp_list *fpl, struct unix_sock *receiver);
+void unix_del_edges(struct scm_fp_list *fpl);
int unix_alloc_edges(struct scm_fp_list *fpl);
void unix_free_edges(struct scm_fp_list *fpl);
void unix_gc(void);
diff --git a/include/net/scm.h b/include/net/scm.h
index a1142dee086c..7d807fe466a3 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 unix_edge *edges;
#endif
struct user_struct *user;
diff --git a/net/core/scm.c b/net/core/scm.c
index bc75b6927222..cad0c153ac93 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -88,6 +88,7 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
fpl->count = 0;
fpl->count_unix = 0;
#if IS_ENABLED(CONFIG_UNIX)
+ fpl->inflight = false;
fpl->edges = NULL;
#endif
fpl->max = SCM_MAX_FD;
@@ -381,6 +382,7 @@ struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
get_file(fpl->fp[i]);
#if IS_ENABLED(CONFIG_UNIX)
+ new_fpl->inflight = false;
new_fpl->edges = NULL;
#endif
new_fpl->max = new_fpl->count;
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 0391f66546a6..ea7bac18a781 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1956,8 +1956,10 @@ 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)
@@ -1965,8 +1967,10 @@ 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 ec998c7d6b4c..353416f38738 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -109,6 +109,57 @@ void unix_init_vertex(struct unix_sock *u)
INIT_LIST_HEAD(&vertex->edges);
}
+DEFINE_SPINLOCK(unix_gc_lock);
+static LIST_HEAD(unix_unvisited_vertices);
+
+void unix_add_edges(struct scm_fp_list *fpl, struct unix_sock *receiver)
+{
+ int i = 0, j = 0;
+
+ spin_lock(&unix_gc_lock);
+
+ while (i < fpl->count_unix) {
+ struct unix_sock *inflight = unix_get_socket(fpl->fp[j++]);
+ struct unix_edge *edge;
+
+ if (!inflight)
+ continue;
+
+ edge = fpl->edges + i++;
+ edge->predecessor = &inflight->vertex;
+ edge->successor = &receiver->vertex;
+
+ if (!edge->predecessor->out_degree++)
+ list_add_tail(&edge->predecessor->entry, &unix_unvisited_vertices);
+
+ list_add_tail(&edge->entry, &edge->predecessor->edges);
+ }
+
+ spin_unlock(&unix_gc_lock);
+
+ fpl->inflight = true;
+}
+
+void unix_del_edges(struct scm_fp_list *fpl)
+{
+ int i = 0;
+
+ spin_lock(&unix_gc_lock);
+
+ while (i < fpl->count_unix) {
+ struct unix_edge *edge = fpl->edges + i++;
+
+ list_del(&edge->entry);
+
+ if (!--edge->predecessor->out_degree)
+ list_del_init(&edge->predecessor->entry);
+ }
+
+ spin_unlock(&unix_gc_lock);
+
+ fpl->inflight = false;
+}
+
int unix_alloc_edges(struct scm_fp_list *fpl)
{
if (!fpl->count_unix)
@@ -124,10 +175,12 @@ int unix_alloc_edges(struct scm_fp_list *fpl)
void unix_free_edges(struct scm_fp_list *fpl)
{
+ if (fpl->inflight)
+ unix_del_edges(fpl);
+
kvfree(fpl->edges);
}
-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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