This is a note to let you know that I've just added the patch titled
af_unix: Allocate struct unix_vertex for each inflight AF_UNIX fd.
to the 6.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
af_unix-allocate-struct-unix_vertex-for-each-infligh.patch
and it can be found in the queue-6.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 2c81612444e1e204161559f10885b1e9de76e20c
Author: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Date: Mon Mar 25 13:24:11 2024 -0700
af_unix: Allocate struct unix_vertex for each inflight AF_UNIX fd.
[ Upstream commit 1fbfdfaa590248c1d86407f578e40e5c65136330 ]
We will replace the garbage collection algorithm for AF_UNIX, where
we will consider each inflight AF_UNIX socket as a vertex and its file
descriptor as an edge in a directed graph.
This patch introduces a new struct unix_vertex representing a vertex
in the graph and adds its pointer to struct unix_sock.
When we send a fd using the SCM_RIGHTS message, we allocate struct
scm_fp_list to struct scm_cookie in scm_fp_copy(). Then, we bump
each refcount of the inflight fds' struct file and save them in
scm_fp_list.fp.
After that, unix_attach_fds() inexplicably clones scm_fp_list of
scm_cookie and sets it to skb. (We will remove this part after
replacing GC.)
Here, we add a new function call in unix_attach_fds() to preallocate
struct unix_vertex per inflight AF_UNIX fd and link each vertex to
skb's scm_fp_list.vertices.
When sendmsg() succeeds later, if the socket of the inflight fd is
still not inflight yet, we will set the preallocated vertex to struct
unix_sock.vertex and link it to a global list unix_unvisited_vertices
under spin_lock(&unix_gc_lock).
If the socket is already inflight, we free the preallocated vertex.
This is to avoid taking the lock unnecessarily when sendmsg() could
fail later.
In the following patch, we will similarly allocate another struct
per edge, which will finally be linked to the inflight socket's
unix_vertex.edges.
And then, we will count the number of edges as unix_vertex.out_degree.
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Acked-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240325202425.60930-2-kuniyu@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Stable-dep-of: 1b536948e805 ("af_unix: Annotate data-race of sk->sk_state in unix_accept().")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index 3dee0b2721aa4..07f0f698c9490 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -22,9 +22,17 @@ 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);
+int unix_prepare_fpl(struct scm_fp_list *fpl);
+void unix_destroy_fpl(struct scm_fp_list *fpl);
void unix_gc(void);
void wait_for_unix_gc(struct scm_fp_list *fpl);
+struct unix_vertex {
+ struct list_head edges;
+ struct list_head entry;
+ unsigned long out_degree;
+};
+
struct sock *unix_peer_get(struct sock *sk);
#define UNIX_HASH_MOD (256 - 1)
@@ -62,6 +70,7 @@ struct unix_sock {
struct path path;
struct mutex iolock, bindlock;
struct sock *peer;
+ struct unix_vertex *vertex;
struct list_head link;
unsigned long inflight;
spinlock_t lock;
diff --git a/include/net/scm.h b/include/net/scm.h
index 92276a2c55436..e34321b6e204b 100644
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -27,6 +27,9 @@ struct scm_fp_list {
short count;
short count_unix;
short max;
+#ifdef CONFIG_UNIX
+ struct list_head vertices;
+#endif
struct user_struct *user;
struct file *fp[SCM_MAX_FD];
};
diff --git a/net/core/scm.c b/net/core/scm.c
index 9cd4b0a01cd60..87dfec1c33787 100644
--- a/net/core/scm.c
+++ b/net/core/scm.c
@@ -89,6 +89,9 @@ static int scm_fp_copy(struct cmsghdr *cmsg, struct scm_fp_list **fplp)
fpl->count_unix = 0;
fpl->max = SCM_MAX_FD;
fpl->user = NULL;
+#if IS_ENABLED(CONFIG_UNIX)
+ INIT_LIST_HEAD(&fpl->vertices);
+#endif
}
fpp = &fpl->fp[fpl->count];
@@ -376,8 +379,12 @@ struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl)
if (new_fpl) {
for (i = 0; i < fpl->count; i++)
get_file(fpl->fp[i]);
+
new_fpl->max = new_fpl->count;
new_fpl->user = get_uid(fpl->user);
+#if IS_ENABLED(CONFIG_UNIX)
+ INIT_LIST_HEAD(&new_fpl->vertices);
+#endif
}
return new_fpl;
}
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index cbc011ceb89b4..4100541c8c00f 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -974,6 +974,7 @@ static struct sock *unix_create1(struct net *net, struct socket *sock, int kern,
sk->sk_destruct = unix_sock_destructor;
u = unix_sk(sk);
u->inflight = 0;
+ u->vertex = NULL;
u->path.dentry = NULL;
u->path.mnt = NULL;
spin_lock_init(&u->lock);
@@ -1808,6 +1809,9 @@ static int unix_attach_fds(struct scm_cookie *scm, struct sk_buff *skb)
for (i = scm->fp->count - 1; i >= 0; i--)
unix_inflight(scm->fp->user, scm->fp->fp[i]);
+ if (unix_prepare_fpl(UNIXCB(skb).fp))
+ return -ENOMEM;
+
return 0;
}
@@ -1818,6 +1822,8 @@ static void unix_detach_fds(struct scm_cookie *scm, struct sk_buff *skb)
scm->fp = UNIXCB(skb).fp;
UNIXCB(skb).fp = NULL;
+ unix_destroy_fpl(scm->fp);
+
for (i = scm->fp->count - 1; i >= 0; i--)
unix_notinflight(scm->fp->user, scm->fp->fp[i]);
}
diff --git a/net/unix/garbage.c b/net/unix/garbage.c
index 0104be9d47045..8ea7640e032e8 100644
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -101,6 +101,44 @@ struct unix_sock *unix_get_socket(struct file *filp)
return NULL;
}
+static void unix_free_vertices(struct scm_fp_list *fpl)
+{
+ struct unix_vertex *vertex, *next_vertex;
+
+ list_for_each_entry_safe(vertex, next_vertex, &fpl->vertices, entry) {
+ list_del(&vertex->entry);
+ kfree(vertex);
+ }
+}
+
+int unix_prepare_fpl(struct scm_fp_list *fpl)
+{
+ struct unix_vertex *vertex;
+ int i;
+
+ if (!fpl->count_unix)
+ return 0;
+
+ for (i = 0; i < fpl->count_unix; i++) {
+ vertex = kmalloc(sizeof(*vertex), GFP_KERNEL);
+ if (!vertex)
+ goto err;
+
+ list_add(&vertex->entry, &fpl->vertices);
+ }
+
+ return 0;
+
+err:
+ unix_free_vertices(fpl);
+ return -ENOMEM;
+}
+
+void unix_destroy_fpl(struct scm_fp_list *fpl)
+{
+ unix_free_vertices(fpl);
+}
+
DEFINE_SPINLOCK(unix_gc_lock);
unsigned int unix_tot_inflight;
static LIST_HEAD(gc_candidates);
