af_unix: Allocate struct unix_edge for each inflight AF_UNIX fd.

As with the previous patch, we preallocate to skb's scm_fp_list an
array of struct unix_edge in the number of inflight AF_UNIX fds.

There we just preallocate memory and do not use immediately because
sendmsg() could fail after this point.  The actual use will be in
the next patch.

When we queue skb with inflight edges, we will set the inflight
socket's unix_sock as unix_edge->predecessor and the receiver's
unix_sock as successor, and then we will link the edge to the
inflight socket's unix_vertex.edges.

Note that we set NULL to cloned scm_fp_list.edges in scm_fp_dup()
so that MSG_PEEK does not change the shape of the directed graph.

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Link: https://lore.kernel.org/r/20240325202425.60930-3-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index c270877a5256dfd77e7775bd1e9bb2e9f8cbfd96..55c4abc26a71438d5e78bae09934ff817a37325a 100644 (file)
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -33,6 +33,12 @@ struct unix_vertex {
        unsigned long out_degree;
 };
 
+struct unix_edge {
+       struct unix_sock *predecessor;
+       struct unix_sock *successor;
+       struct list_head vertex_entry;
+};
+
 struct sock *unix_peer_get(struct sock *sk);
 
 #define UNIX_HASH_MOD  (256 - 1)

diff --git a/include/net/scm.h b/include/net/scm.h
index e34321b6e204ba8fb29fdd23d613f4361fd7116e..5f5154e5096dc5bf5339353de31925a57157310a 100644 (file)
--- a/include/net/scm.h
+++ b/include/net/scm.h
@@ -23,12 +23,17 @@ struct scm_creds {
        kgid_t  gid;
 };
 
+#ifdef CONFIG_UNIX
+struct unix_edge;
+#endif
+
 struct scm_fp_list {
        short                   count;
        short                   count_unix;
        short                   max;
 #ifdef CONFIG_UNIX
        struct list_head        vertices;
+       struct unix_edge        *edges;
 #endif
        struct user_struct      *user;
        struct file             *fp[SCM_MAX_FD];

diff --git a/net/core/scm.c b/net/core/scm.c
index 87dfec1c33787db12f6e859348943019def42046..1bcc8a2d65e3fa055ac2fc411ed6c5db41403356 100644 (file)
--- 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->edges = NULL;
                INIT_LIST_HEAD(&fpl->vertices);
 #endif
        }
@@ -383,6 +384,7 @@ 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->edges = NULL;
                INIT_LIST_HEAD(&new_fpl->vertices);
 #endif
        }

diff --git a/net/unix/garbage.c b/net/unix/garbage.c
index 75bdf66b81df7a5514c14db790ceed707e76d725..f31917683288b082141238c149675794a0e8f7a1 100644 (file)
--- a/net/unix/garbage.c
+++ b/net/unix/garbage.c
@@ -127,6 +127,11 @@ int unix_prepare_fpl(struct scm_fp_list *fpl)
                list_add(&vertex->entry, &fpl->vertices);
        }
 
+       fpl->edges = kvmalloc_array(fpl->count_unix, sizeof(*fpl->edges),
+                                   GFP_KERNEL_ACCOUNT);
+       if (!fpl->edges)
+               goto err;
+
        return 0;
 
 err:
@@ -136,6 +141,7 @@ err:
 
 void unix_destroy_fpl(struct scm_fp_list *fpl)
 {
+       kvfree(fpl->edges);
        unix_free_vertices(fpl);
 }