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To garbage collect inflight AF_UNIX sockets, we must define the
cyclic reference appropriately. This is a bit tricky if the loop
consists of embryo sockets.
Suppose that the fd of AF_UNIX socket A is passed to D and the fd B
to C and that C and D are embryo sockets of A and B, respectively.
It may appear that there are two separate graphs, A (-> D) and
B (-> C), but this is not correct.
A --. .-- B
X
C <-' `-> D
Now, D holds A's refcount, and C has B's refcount, so unix_release()
will never be called for A and B when we close() them. However, no
one can call close() for D and C to free skbs holding refcounts of A
and B because C/D is in A/B's receive queue, which should have been
purged by unix_release() for A and B.
So, here's another type of cyclic reference. When a fd of an AF_UNIX
socket is passed to an embryo socket, the reference is indirectly held
by its parent listening socket.
.-> A .-> B
| `- sk_receive_queue | `- sk_receive_queue
| `- skb | `- skb
| `- sk == C | `- sk == D
| `- sk_receive_queue | `- sk_receive_queue
| `- skb +---------' `- skb +-.
| |
`---------------------------------------------------------'
Technically, the graph must be denoted as A <-> B instead of A (-> D)
and B (-> C) to find such a cyclic reference without touching each
socket's receive queue.
.-> A --. .-- B <-.
| X | == A <-> B
`-- C <-' `-> D --'
We apply this fixup during GC by fetching the real successor by
unix_edge_successor().
When we call accept(), we clear unix_sock.listener under unix_gc_lock
not to confuse GC.
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Link: https://lore.kernel.org/r/20240325202425.60930-9-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
148 lines
3.9 KiB
C
148 lines
3.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __LINUX_NET_AFUNIX_H
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#define __LINUX_NET_AFUNIX_H
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#include <linux/socket.h>
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#include <linux/un.h>
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#include <linux/mutex.h>
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#include <linux/refcount.h>
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#include <net/sock.h>
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#if IS_ENABLED(CONFIG_UNIX)
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struct unix_sock *unix_get_socket(struct file *filp);
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#else
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static inline struct unix_sock *unix_get_socket(struct file *filp)
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{
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return NULL;
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}
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#endif
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extern spinlock_t unix_gc_lock;
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extern unsigned int unix_tot_inflight;
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void unix_inflight(struct user_struct *user, struct file *fp);
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void unix_notinflight(struct user_struct *user, struct file *fp);
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void unix_add_edges(struct scm_fp_list *fpl, struct unix_sock *receiver);
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void unix_del_edges(struct scm_fp_list *fpl);
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void unix_update_edges(struct unix_sock *receiver);
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int unix_prepare_fpl(struct scm_fp_list *fpl);
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void unix_destroy_fpl(struct scm_fp_list *fpl);
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void unix_gc(void);
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void wait_for_unix_gc(struct scm_fp_list *fpl);
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struct unix_vertex {
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struct list_head edges;
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struct list_head entry;
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struct list_head scc_entry;
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unsigned long out_degree;
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unsigned long index;
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unsigned long lowlink;
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bool on_stack;
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};
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struct unix_edge {
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struct unix_sock *predecessor;
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struct unix_sock *successor;
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struct list_head vertex_entry;
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struct list_head stack_entry;
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};
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struct sock *unix_peer_get(struct sock *sk);
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#define UNIX_HASH_MOD (256 - 1)
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#define UNIX_HASH_SIZE (256 * 2)
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#define UNIX_HASH_BITS 8
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struct unix_address {
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refcount_t refcnt;
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int len;
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struct sockaddr_un name[];
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};
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struct unix_skb_parms {
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struct pid *pid; /* Skb credentials */
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kuid_t uid;
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kgid_t gid;
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struct scm_fp_list *fp; /* Passed files */
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#ifdef CONFIG_SECURITY_NETWORK
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u32 secid; /* Security ID */
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#endif
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u32 consumed;
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} __randomize_layout;
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struct scm_stat {
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atomic_t nr_fds;
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};
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#define UNIXCB(skb) (*(struct unix_skb_parms *)&((skb)->cb))
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/* The AF_UNIX socket */
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struct unix_sock {
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/* WARNING: sk has to be the first member */
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struct sock sk;
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struct unix_address *addr;
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struct path path;
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struct mutex iolock, bindlock;
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struct sock *peer;
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struct sock *listener;
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struct unix_vertex *vertex;
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struct list_head link;
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unsigned long inflight;
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spinlock_t lock;
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unsigned long gc_flags;
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#define UNIX_GC_CANDIDATE 0
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#define UNIX_GC_MAYBE_CYCLE 1
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struct socket_wq peer_wq;
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wait_queue_entry_t peer_wake;
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struct scm_stat scm_stat;
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#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
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struct sk_buff *oob_skb;
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#endif
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};
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#define unix_sk(ptr) container_of_const(ptr, struct unix_sock, sk)
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#define unix_peer(sk) (unix_sk(sk)->peer)
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#define unix_state_lock(s) spin_lock(&unix_sk(s)->lock)
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#define unix_state_unlock(s) spin_unlock(&unix_sk(s)->lock)
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enum unix_socket_lock_class {
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U_LOCK_NORMAL,
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U_LOCK_SECOND, /* for double locking, see unix_state_double_lock(). */
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U_LOCK_DIAG, /* used while dumping icons, see sk_diag_dump_icons(). */
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};
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static inline void unix_state_lock_nested(struct sock *sk,
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enum unix_socket_lock_class subclass)
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{
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spin_lock_nested(&unix_sk(sk)->lock, subclass);
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}
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#define peer_wait peer_wq.wait
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long unix_inq_len(struct sock *sk);
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long unix_outq_len(struct sock *sk);
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int __unix_dgram_recvmsg(struct sock *sk, struct msghdr *msg, size_t size,
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int flags);
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int __unix_stream_recvmsg(struct sock *sk, struct msghdr *msg, size_t size,
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int flags);
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#ifdef CONFIG_SYSCTL
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int unix_sysctl_register(struct net *net);
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void unix_sysctl_unregister(struct net *net);
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#else
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static inline int unix_sysctl_register(struct net *net) { return 0; }
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static inline void unix_sysctl_unregister(struct net *net) {}
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#endif
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#ifdef CONFIG_BPF_SYSCALL
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extern struct proto unix_dgram_proto;
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extern struct proto unix_stream_proto;
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int unix_dgram_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore);
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int unix_stream_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore);
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void __init unix_bpf_build_proto(void);
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#else
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static inline void __init unix_bpf_build_proto(void)
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{}
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#endif
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#endif
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