[PATCH v1 net-next 03/16] af_unix: Link struct unix_edge when queuing skb.
From: Kuniyuki Iwashima <hidden>
Date: 2024-02-03 03:02:29
Subsystem:
networking [general], networking [sockets], networking [unix sockets], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Kuniyuki Iwashima, Willem de Bruijn, Linus Torvalds
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 <redacted>
---
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 | 56 ++++++++++++++++++++++++++++++++++++++++++-
5 files changed, 66 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 8661524ed6e5..d141c00eb116 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c@@ -87,6 +87,7 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp) *fplp = fpl; fpl->count = 0; fpl->count_unix = 0; + fpl->inflight = false; fpl->edges = NULL; fpl->max = SCM_MAX_FD; fpl->user = NULL;
@@ -378,6 +379,7 @@ struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl) for (i = 0; i < fpl->count; i++) get_file(fpl->fp[i]); + new_fpl->inflight = false; new_fpl->edges = NULL; new_fpl->max = new_fpl->count; new_fpl->user = get_uid(fpl->user);
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 6a3572e43b9f..572ac0994c69 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c@@ -110,6 +110,58 @@ void unix_init_vertex(struct unix_sock *u) INIT_LIST_HEAD(&vertex->entry); } +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); + + INIT_LIST_HEAD(&edge->entry); + 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)
@@ -125,10 +177,12 @@ 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