Contributors: 21
| Author |
Tokens |
Token Proportion |
Commits |
Commit Proportion |
| Miklos Szeredi |
565 |
41.70% |
2 |
3.23% |
| Linus Torvalds (pre-git) |
283 |
20.89% |
19 |
30.65% |
| Kuniyuki Iwashima |
215 |
15.87% |
12 |
19.35% |
| Eric Dumazet |
90 |
6.64% |
4 |
6.45% |
| Jens Axboe |
61 |
4.50% |
1 |
1.61% |
| Michal Luczaj |
31 |
2.29% |
1 |
1.61% |
| Al Viro |
16 |
1.18% |
4 |
6.45% |
| Jason Eastman |
14 |
1.03% |
1 |
1.61% |
| Pavel Emelyanov |
13 |
0.96% |
2 |
3.23% |
| Arnaldo Carvalho de Melo |
12 |
0.89% |
3 |
4.84% |
| dann frazier |
12 |
0.89% |
1 |
1.61% |
| David S. Miller |
10 |
0.74% |
3 |
4.84% |
| Hannes Frederic Sowa |
10 |
0.74% |
1 |
1.61% |
| Ilpo Järvinen |
8 |
0.59% |
1 |
1.61% |
| Matthew Wilcox |
4 |
0.30% |
1 |
1.61% |
| Arjan van de Ven |
3 |
0.22% |
1 |
1.61% |
| Willy Tarreau |
2 |
0.15% |
1 |
1.61% |
| Thomas Gleixner |
2 |
0.15% |
1 |
1.61% |
| Pavel Begunkov |
2 |
0.15% |
1 |
1.61% |
| Linus Torvalds |
1 |
0.07% |
1 |
1.61% |
| Andrew Morton |
1 |
0.07% |
1 |
1.61% |
| Total |
1355 |
|
62 |
|
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* NET3: Garbage Collector For AF_UNIX sockets
*
* Garbage Collector:
* Copyright (C) Barak A. Pearlmutter.
*
* Chopped about by Alan Cox 22/3/96 to make it fit the AF_UNIX socket problem.
* If it doesn't work blame me, it worked when Barak sent it.
*
* Assumptions:
*
* - object w/ a bit
* - free list
*
* Current optimizations:
*
* - explicit stack instead of recursion
* - tail recurse on first born instead of immediate push/pop
* - we gather the stuff that should not be killed into tree
* and stack is just a path from root to the current pointer.
*
* Future optimizations:
*
* - don't just push entire root set; process in place
*
* Fixes:
* Alan Cox 07 Sept 1997 Vmalloc internal stack as needed.
* Cope with changing max_files.
* Al Viro 11 Oct 1998
* Graph may have cycles. That is, we can send the descriptor
* of foo to bar and vice versa. Current code chokes on that.
* Fix: move SCM_RIGHTS ones into the separate list and then
* skb_free() them all instead of doing explicit fput's.
* Another problem: since fput() may block somebody may
* create a new unix_socket when we are in the middle of sweep
* phase. Fix: revert the logic wrt MARKED. Mark everything
* upon the beginning and unmark non-junk ones.
*
* [12 Oct 1998] AAARGH! New code purges all SCM_RIGHTS
* sent to connect()'ed but still not accept()'ed sockets.
* Fixed. Old code had slightly different problem here:
* extra fput() in situation when we passed the descriptor via
* such socket and closed it (descriptor). That would happen on
* each unix_gc() until the accept(). Since the struct file in
* question would go to the free list and might be reused...
* That might be the reason of random oopses on filp_close()
* in unrelated processes.
*
* AV 28 Feb 1999
* Kill the explicit allocation of stack. Now we keep the tree
* with root in dummy + pointer (gc_current) to one of the nodes.
* Stack is represented as path from gc_current to dummy. Unmark
* now means "add to tree". Push == "make it a son of gc_current".
* Pop == "move gc_current to parent". We keep only pointers to
* parents (->gc_tree).
* AV 1 Mar 1999
* Damn. Added missing check for ->dead in listen queues scanning.
*
* Miklos Szeredi 25 Jun 2007
* Reimplement with a cycle collecting algorithm. This should
* solve several problems with the previous code, like being racy
* wrt receive and holding up unrelated socket operations.
*/
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/socket.h>
#include <linux/un.h>
#include <linux/net.h>
#include <linux/fs.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/file.h>
#include <linux/proc_fs.h>
#include <linux/mutex.h>
#include <linux/wait.h>
#include <net/sock.h>
#include <net/af_unix.h>
#include <net/scm.h>
#include <net/tcp_states.h>
struct unix_sock *unix_get_socket(struct file *filp)
{
struct inode *inode = file_inode(filp);
/* Socket ? */
if (S_ISSOCK(inode->i_mode) && !(filp->f_mode & FMODE_PATH)) {
struct socket *sock = SOCKET_I(inode);
const struct proto_ops *ops;
struct sock *sk = sock->sk;
ops = READ_ONCE(sock->ops);
/* PF_UNIX ? */
if (sk && ops && ops->family == PF_UNIX)
return unix_sk(sk);
}
return NULL;
}
DEFINE_SPINLOCK(unix_gc_lock);
unsigned int unix_tot_inflight;
static LIST_HEAD(gc_candidates);
static LIST_HEAD(gc_inflight_list);
/* Keep the number of times in flight count for the file
* descriptor if it is for an AF_UNIX socket.
*/
void unix_inflight(struct user_struct *user, struct file *filp)
{
struct unix_sock *u = unix_get_socket(filp);
spin_lock(&unix_gc_lock);
if (u) {
if (!u->inflight) {
WARN_ON_ONCE(!list_empty(&u->link));
list_add_tail(&u->link, &gc_inflight_list);
} else {
WARN_ON_ONCE(list_empty(&u->link));
}
u->inflight++;
/* Paired with READ_ONCE() in wait_for_unix_gc() */
WRITE_ONCE(unix_tot_inflight, unix_tot_inflight + 1);
}
WRITE_ONCE(user->unix_inflight, user->unix_inflight + 1);
spin_unlock(&unix_gc_lock);
}
void unix_notinflight(struct user_struct *user, struct file *filp)
{
struct unix_sock *u = unix_get_socket(filp);
spin_lock(&unix_gc_lock);
if (u) {
WARN_ON_ONCE(!u->inflight);
WARN_ON_ONCE(list_empty(&u->link));
u->inflight--;
if (!u->inflight)
list_del_init(&u->link);
/* Paired with READ_ONCE() in wait_for_unix_gc() */
WRITE_ONCE(unix_tot_inflight, unix_tot_inflight - 1);
}
WRITE_ONCE(user->unix_inflight, user->unix_inflight - 1);
spin_unlock(&unix_gc_lock);
}
static void scan_inflight(struct sock *x, void (*func)(struct unix_sock *),
struct sk_buff_head *hitlist)
{
struct sk_buff *skb;
struct sk_buff *next;
spin_lock(&x->sk_receive_queue.lock);
skb_queue_walk_safe(&x->sk_receive_queue, skb, next) {
/* Do we have file descriptors ? */
if (UNIXCB(skb).fp) {
bool hit = false;
/* Process the descriptors of this socket */
int nfd = UNIXCB(skb).fp->count;
struct file **fp = UNIXCB(skb).fp->fp;
while (nfd--) {
/* Get the socket the fd matches if it indeed does so */
struct unix_sock *u = unix_get_socket(*fp++);
/* Ignore non-candidates, they could have been added
* to the queues after starting the garbage collection
*/
if (u && test_bit(UNIX_GC_CANDIDATE, &u->gc_flags)) {
hit = true;
func(u);
}
}
if (hit && hitlist != NULL) {
__skb_unlink(skb, &x->sk_receive_queue);
__skb_queue_tail(hitlist, skb);
}
}
}
spin_unlock(&x->sk_receive_queue.lock);
}
static void scan_children(struct sock *x, void (*func)(struct unix_sock *),
struct sk_buff_head *hitlist)
{
if (x->sk_state != TCP_LISTEN) {
scan_inflight(x, func, hitlist);
} else {
struct sk_buff *skb;
struct sk_buff *next;
struct unix_sock *u;
LIST_HEAD(embryos);
/* For a listening socket collect the queued embryos
* and perform a scan on them as well.
*/
spin_lock(&x->sk_receive_queue.lock);
skb_queue_walk_safe(&x->sk_receive_queue, skb, next) {
u = unix_sk(skb->sk);
/* An embryo cannot be in-flight, so it's safe
* to use the list link.
*/
WARN_ON_ONCE(!list_empty(&u->link));
list_add_tail(&u->link, &embryos);
}
spin_unlock(&x->sk_receive_queue.lock);
while (!list_empty(&embryos)) {
u = list_entry(embryos.next, struct unix_sock, link);
scan_inflight(&u->sk, func, hitlist);
list_del_init(&u->link);
}
}
}
static void dec_inflight(struct unix_sock *usk)
{
usk->inflight--;
}
static void inc_inflight(struct unix_sock *usk)
{
usk->inflight++;
}
static void inc_inflight_move_tail(struct unix_sock *u)
{
u->inflight++;
/* If this still might be part of a cycle, move it to the end
* of the list, so that it's checked even if it was already
* passed over
*/
if (test_bit(UNIX_GC_MAYBE_CYCLE, &u->gc_flags))
list_move_tail(&u->link, &gc_candidates);
}
static bool gc_in_progress;
static void __unix_gc(struct work_struct *work)
{
struct sk_buff_head hitlist;
struct unix_sock *u, *next;
LIST_HEAD(not_cycle_list);
struct list_head cursor;
spin_lock(&unix_gc_lock);
/* First, select candidates for garbage collection. Only
* in-flight sockets are considered, and from those only ones
* which don't have any external reference.
*
* Holding unix_gc_lock will protect these candidates from
* being detached, and hence from gaining an external
* reference. Since there are no possible receivers, all
* buffers currently on the candidates' queues stay there
* during the garbage collection.
*
* We also know that no new candidate can be added onto the
* receive queues. Other, non candidate sockets _can_ be
* added to queue, so we must make sure only to touch
* candidates.
*
* Embryos, though never candidates themselves, affect which
* candidates are reachable by the garbage collector. Before
* being added to a listener's queue, an embryo may already
* receive data carrying SCM_RIGHTS, potentially making the
* passed socket a candidate that is not yet reachable by the
* collector. It becomes reachable once the embryo is
* enqueued. Therefore, we must ensure that no SCM-laden
* embryo appears in a (candidate) listener's queue between
* consecutive scan_children() calls.
*/
list_for_each_entry_safe(u, next, &gc_inflight_list, link) {
struct sock *sk = &u->sk;
long total_refs;
total_refs = file_count(sk->sk_socket->file);
WARN_ON_ONCE(!u->inflight);
WARN_ON_ONCE(total_refs < u->inflight);
if (total_refs == u->inflight) {
list_move_tail(&u->link, &gc_candidates);
__set_bit(UNIX_GC_CANDIDATE, &u->gc_flags);
__set_bit(UNIX_GC_MAYBE_CYCLE, &u->gc_flags);
if (sk->sk_state == TCP_LISTEN) {
unix_state_lock_nested(sk, U_LOCK_GC_LISTENER);
unix_state_unlock(sk);
}
}
}
/* Now remove all internal in-flight reference to children of
* the candidates.
*/
list_for_each_entry(u, &gc_candidates, link)
scan_children(&u->sk, dec_inflight, NULL);
/* Restore the references for children of all candidates,
* which have remaining references. Do this recursively, so
* only those remain, which form cyclic references.
*
* Use a "cursor" link, to make the list traversal safe, even
* though elements might be moved about.
*/
list_add(&cursor, &gc_candidates);
while (cursor.next != &gc_candidates) {
u = list_entry(cursor.next, struct unix_sock, link);
/* Move cursor to after the current position. */
list_move(&cursor, &u->link);
if (u->inflight) {
list_move_tail(&u->link, ¬_cycle_list);
__clear_bit(UNIX_GC_MAYBE_CYCLE, &u->gc_flags);
scan_children(&u->sk, inc_inflight_move_tail, NULL);
}
}
list_del(&cursor);
/* Now gc_candidates contains only garbage. Restore original
* inflight counters for these as well, and remove the skbuffs
* which are creating the cycle(s).
*/
skb_queue_head_init(&hitlist);
list_for_each_entry(u, &gc_candidates, link) {
scan_children(&u->sk, inc_inflight, &hitlist);
#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
if (u->oob_skb) {
kfree_skb(u->oob_skb);
u->oob_skb = NULL;
}
#endif
}
/* not_cycle_list contains those sockets which do not make up a
* cycle. Restore these to the inflight list.
*/
while (!list_empty(¬_cycle_list)) {
u = list_entry(not_cycle_list.next, struct unix_sock, link);
__clear_bit(UNIX_GC_CANDIDATE, &u->gc_flags);
list_move_tail(&u->link, &gc_inflight_list);
}
spin_unlock(&unix_gc_lock);
/* Here we are. Hitlist is filled. Die. */
__skb_queue_purge(&hitlist);
spin_lock(&unix_gc_lock);
/* All candidates should have been detached by now. */
WARN_ON_ONCE(!list_empty(&gc_candidates));
/* Paired with READ_ONCE() in wait_for_unix_gc(). */
WRITE_ONCE(gc_in_progress, false);
spin_unlock(&unix_gc_lock);
}
static DECLARE_WORK(unix_gc_work, __unix_gc);
void unix_gc(void)
{
WRITE_ONCE(gc_in_progress, true);
queue_work(system_unbound_wq, &unix_gc_work);
}
#define UNIX_INFLIGHT_TRIGGER_GC 16000
#define UNIX_INFLIGHT_SANE_USER (SCM_MAX_FD * 8)
void wait_for_unix_gc(struct scm_fp_list *fpl)
{
/* If number of inflight sockets is insane,
* force a garbage collect right now.
*
* Paired with the WRITE_ONCE() in unix_inflight(),
* unix_notinflight(), and __unix_gc().
*/
if (READ_ONCE(unix_tot_inflight) > UNIX_INFLIGHT_TRIGGER_GC &&
!READ_ONCE(gc_in_progress))
unix_gc();
/* Penalise users who want to send AF_UNIX sockets
* but whose sockets have not been received yet.
*/
if (!fpl || !fpl->count_unix ||
READ_ONCE(fpl->user->unix_inflight) < UNIX_INFLIGHT_SANE_USER)
return;
if (READ_ONCE(gc_in_progress))
flush_work(&unix_gc_work);
}