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![Xin Long](/assets/img/avatar_default.png)
This patch is to delay the endpoint free by calling call_rcu() to fix
another use-after-free issue in sctp_sock_dump():
BUG: KASAN: use-after-free in __lock_acquire+0x36d9/0x4c20
Call Trace:
__lock_acquire+0x36d9/0x4c20 kernel/locking/lockdep.c:3218
lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
__raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
_raw_spin_lock_bh+0x31/0x40 kernel/locking/spinlock.c:168
spin_lock_bh include/linux/spinlock.h:334 [inline]
__lock_sock+0x203/0x350 net/core/sock.c:2253
lock_sock_nested+0xfe/0x120 net/core/sock.c:2774
lock_sock include/net/sock.h:1492 [inline]
sctp_sock_dump+0x122/0xb20 net/sctp/diag.c:324
sctp_for_each_transport+0x2b5/0x370 net/sctp/socket.c:5091
sctp_diag_dump+0x3ac/0x660 net/sctp/diag.c:527
__inet_diag_dump+0xa8/0x140 net/ipv4/inet_diag.c:1049
inet_diag_dump+0x9b/0x110 net/ipv4/inet_diag.c:1065
netlink_dump+0x606/0x1080 net/netlink/af_netlink.c:2244
__netlink_dump_start+0x59a/0x7c0 net/netlink/af_netlink.c:2352
netlink_dump_start include/linux/netlink.h:216 [inline]
inet_diag_handler_cmd+0x2ce/0x3f0 net/ipv4/inet_diag.c:1170
__sock_diag_cmd net/core/sock_diag.c:232 [inline]
sock_diag_rcv_msg+0x31d/0x410 net/core/sock_diag.c:263
netlink_rcv_skb+0x172/0x440 net/netlink/af_netlink.c:2477
sock_diag_rcv+0x2a/0x40 net/core/sock_diag.c:274
This issue occurs when asoc is peeled off and the old sk is freed after
getting it by asoc->base.sk and before calling lock_sock(sk).
To prevent the sk free, as a holder of the sk, ep should be alive when
calling lock_sock(). This patch uses call_rcu() and moves sock_put and
ep free into sctp_endpoint_destroy_rcu(), so that it's safe to try to
hold the ep under rcu_read_lock in sctp_transport_traverse_process().
If sctp_endpoint_hold() returns true, it means this ep is still alive
and we have held it and can continue to dump it; If it returns false,
it means this ep is dead and can be freed after rcu_read_unlock, and
we should skip it.
In sctp_sock_dump(), after locking the sk, if this ep is different from
tsp->asoc->ep, it means during this dumping, this asoc was peeled off
before calling lock_sock(), and the sk should be skipped; If this ep is
the same with tsp->asoc->ep, it means no peeloff happens on this asoc,
and due to lock_sock, no peeloff will happen either until release_sock.
Note that delaying endpoint free won't delay the port release, as the
port release happens in sctp_endpoint_destroy() before calling call_rcu().
Also, freeing endpoint by call_rcu() makes it safe to access the sk by
asoc->base.sk in sctp_assocs_seq_show() and sctp_rcv().
Thanks Jones to bring this issue up.
v1->v2:
- improve the changelog.
- add kfree(ep) into sctp_endpoint_destroy_rcu(), as Jakub noticed.
Reported-by: syzbot+9276d76e83e3bcde6c99@syzkaller.appspotmail.com
Reported-by: Lee Jones <lee.jones@linaro.org>
Fixes: d25adbeb0c
("sctp: fix an use-after-free issue in sctp_sock_dump")
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
417 lines
10 KiB
C
417 lines
10 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* SCTP kernel implementation
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* Copyright (c) 1999-2000 Cisco, Inc.
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* Copyright (c) 1999-2001 Motorola, Inc.
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* Copyright (c) 2001-2002 International Business Machines, Corp.
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* Copyright (c) 2001 Intel Corp.
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* Copyright (c) 2001 Nokia, Inc.
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* Copyright (c) 2001 La Monte H.P. Yarroll
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*
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* This file is part of the SCTP kernel implementation
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*
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* This abstraction represents an SCTP endpoint.
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*
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* Please send any bug reports or fixes you make to the
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* email address(es):
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* lksctp developers <linux-sctp@vger.kernel.org>
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*
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* Written or modified by:
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* La Monte H.P. Yarroll <piggy@acm.org>
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* Karl Knutson <karl@athena.chicago.il.us>
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* Jon Grimm <jgrimm@austin.ibm.com>
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* Daisy Chang <daisyc@us.ibm.com>
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* Dajiang Zhang <dajiang.zhang@nokia.com>
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*/
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#include <linux/types.h>
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#include <linux/slab.h>
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#include <linux/in.h>
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#include <linux/random.h> /* get_random_bytes() */
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#include <net/sock.h>
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#include <net/ipv6.h>
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#include <net/sctp/sctp.h>
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#include <net/sctp/sm.h>
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/* Forward declarations for internal helpers. */
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static void sctp_endpoint_bh_rcv(struct work_struct *work);
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/*
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* Initialize the base fields of the endpoint structure.
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*/
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static struct sctp_endpoint *sctp_endpoint_init(struct sctp_endpoint *ep,
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struct sock *sk,
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gfp_t gfp)
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{
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struct net *net = sock_net(sk);
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struct sctp_shared_key *null_key;
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ep->digest = kzalloc(SCTP_SIGNATURE_SIZE, gfp);
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if (!ep->digest)
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return NULL;
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ep->asconf_enable = net->sctp.addip_enable;
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ep->auth_enable = net->sctp.auth_enable;
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if (ep->auth_enable) {
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if (sctp_auth_init(ep, gfp))
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goto nomem;
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if (ep->asconf_enable) {
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sctp_auth_ep_add_chunkid(ep, SCTP_CID_ASCONF);
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sctp_auth_ep_add_chunkid(ep, SCTP_CID_ASCONF_ACK);
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}
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}
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/* Initialize the base structure. */
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/* What type of endpoint are we? */
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ep->base.type = SCTP_EP_TYPE_SOCKET;
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/* Initialize the basic object fields. */
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refcount_set(&ep->base.refcnt, 1);
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ep->base.dead = false;
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/* Create an input queue. */
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sctp_inq_init(&ep->base.inqueue);
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/* Set its top-half handler */
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sctp_inq_set_th_handler(&ep->base.inqueue, sctp_endpoint_bh_rcv);
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/* Initialize the bind addr area */
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sctp_bind_addr_init(&ep->base.bind_addr, 0);
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/* Create the lists of associations. */
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INIT_LIST_HEAD(&ep->asocs);
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/* Use SCTP specific send buffer space queues. */
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ep->sndbuf_policy = net->sctp.sndbuf_policy;
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sk->sk_data_ready = sctp_data_ready;
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sk->sk_write_space = sctp_write_space;
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sock_set_flag(sk, SOCK_USE_WRITE_QUEUE);
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/* Get the receive buffer policy for this endpoint */
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ep->rcvbuf_policy = net->sctp.rcvbuf_policy;
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/* Initialize the secret key used with cookie. */
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get_random_bytes(ep->secret_key, sizeof(ep->secret_key));
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/* SCTP-AUTH extensions*/
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INIT_LIST_HEAD(&ep->endpoint_shared_keys);
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null_key = sctp_auth_shkey_create(0, gfp);
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if (!null_key)
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goto nomem_shkey;
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list_add(&null_key->key_list, &ep->endpoint_shared_keys);
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/* Add the null key to the endpoint shared keys list and
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* set the hmcas and chunks pointers.
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*/
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ep->prsctp_enable = net->sctp.prsctp_enable;
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ep->reconf_enable = net->sctp.reconf_enable;
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ep->ecn_enable = net->sctp.ecn_enable;
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/* Remember who we are attached to. */
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ep->base.sk = sk;
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ep->base.net = sock_net(sk);
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sock_hold(ep->base.sk);
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return ep;
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nomem_shkey:
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sctp_auth_free(ep);
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nomem:
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kfree(ep->digest);
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return NULL;
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}
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/* Create a sctp_endpoint with all that boring stuff initialized.
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* Returns NULL if there isn't enough memory.
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*/
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struct sctp_endpoint *sctp_endpoint_new(struct sock *sk, gfp_t gfp)
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{
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struct sctp_endpoint *ep;
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/* Build a local endpoint. */
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ep = kzalloc(sizeof(*ep), gfp);
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if (!ep)
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goto fail;
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if (!sctp_endpoint_init(ep, sk, gfp))
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goto fail_init;
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SCTP_DBG_OBJCNT_INC(ep);
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return ep;
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fail_init:
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kfree(ep);
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fail:
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return NULL;
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}
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/* Add an association to an endpoint. */
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void sctp_endpoint_add_asoc(struct sctp_endpoint *ep,
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struct sctp_association *asoc)
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{
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struct sock *sk = ep->base.sk;
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/* If this is a temporary association, don't bother
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* since we'll be removing it shortly and don't
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* want anyone to find it anyway.
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*/
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if (asoc->temp)
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return;
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/* Now just add it to our list of asocs */
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list_add_tail(&asoc->asocs, &ep->asocs);
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/* Increment the backlog value for a TCP-style listening socket. */
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if (sctp_style(sk, TCP) && sctp_sstate(sk, LISTENING))
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sk_acceptq_added(sk);
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}
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/* Free the endpoint structure. Delay cleanup until
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* all users have released their reference count on this structure.
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*/
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void sctp_endpoint_free(struct sctp_endpoint *ep)
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{
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ep->base.dead = true;
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inet_sk_set_state(ep->base.sk, SCTP_SS_CLOSED);
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/* Unlink this endpoint, so we can't find it again! */
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sctp_unhash_endpoint(ep);
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sctp_endpoint_put(ep);
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}
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/* Final destructor for endpoint. */
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static void sctp_endpoint_destroy_rcu(struct rcu_head *head)
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{
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struct sctp_endpoint *ep = container_of(head, struct sctp_endpoint, rcu);
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struct sock *sk = ep->base.sk;
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sctp_sk(sk)->ep = NULL;
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sock_put(sk);
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kfree(ep);
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SCTP_DBG_OBJCNT_DEC(ep);
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}
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static void sctp_endpoint_destroy(struct sctp_endpoint *ep)
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{
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struct sock *sk;
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if (unlikely(!ep->base.dead)) {
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WARN(1, "Attempt to destroy undead endpoint %p!\n", ep);
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return;
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}
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/* Free the digest buffer */
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kfree(ep->digest);
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/* SCTP-AUTH: Free up AUTH releated data such as shared keys
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* chunks and hmacs arrays that were allocated
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*/
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sctp_auth_destroy_keys(&ep->endpoint_shared_keys);
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sctp_auth_free(ep);
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/* Cleanup. */
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sctp_inq_free(&ep->base.inqueue);
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sctp_bind_addr_free(&ep->base.bind_addr);
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memset(ep->secret_key, 0, sizeof(ep->secret_key));
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sk = ep->base.sk;
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/* Remove and free the port */
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if (sctp_sk(sk)->bind_hash)
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sctp_put_port(sk);
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call_rcu(&ep->rcu, sctp_endpoint_destroy_rcu);
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}
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/* Hold a reference to an endpoint. */
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int sctp_endpoint_hold(struct sctp_endpoint *ep)
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{
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return refcount_inc_not_zero(&ep->base.refcnt);
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}
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/* Release a reference to an endpoint and clean up if there are
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* no more references.
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*/
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void sctp_endpoint_put(struct sctp_endpoint *ep)
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{
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if (refcount_dec_and_test(&ep->base.refcnt))
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sctp_endpoint_destroy(ep);
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}
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/* Is this the endpoint we are looking for? */
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struct sctp_endpoint *sctp_endpoint_is_match(struct sctp_endpoint *ep,
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struct net *net,
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const union sctp_addr *laddr)
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{
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struct sctp_endpoint *retval = NULL;
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if ((htons(ep->base.bind_addr.port) == laddr->v4.sin_port) &&
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net_eq(ep->base.net, net)) {
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if (sctp_bind_addr_match(&ep->base.bind_addr, laddr,
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sctp_sk(ep->base.sk)))
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retval = ep;
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}
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return retval;
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}
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/* Find the association that goes with this chunk.
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* We lookup the transport from hashtable at first, then get association
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* through t->assoc.
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*/
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struct sctp_association *sctp_endpoint_lookup_assoc(
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const struct sctp_endpoint *ep,
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const union sctp_addr *paddr,
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struct sctp_transport **transport)
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{
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struct sctp_association *asoc = NULL;
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struct sctp_transport *t;
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*transport = NULL;
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/* If the local port is not set, there can't be any associations
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* on this endpoint.
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*/
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if (!ep->base.bind_addr.port)
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return NULL;
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rcu_read_lock();
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t = sctp_epaddr_lookup_transport(ep, paddr);
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if (!t)
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goto out;
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*transport = t;
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asoc = t->asoc;
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out:
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rcu_read_unlock();
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return asoc;
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}
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/* Look for any peeled off association from the endpoint that matches the
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* given peer address.
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*/
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bool sctp_endpoint_is_peeled_off(struct sctp_endpoint *ep,
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const union sctp_addr *paddr)
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{
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struct sctp_sockaddr_entry *addr;
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struct net *net = ep->base.net;
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struct sctp_bind_addr *bp;
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bp = &ep->base.bind_addr;
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/* This function is called with the socket lock held,
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* so the address_list can not change.
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*/
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list_for_each_entry(addr, &bp->address_list, list) {
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if (sctp_has_association(net, &addr->a, paddr))
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return true;
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}
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return false;
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}
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/* Do delayed input processing. This is scheduled by sctp_rcv().
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* This may be called on BH or task time.
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*/
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static void sctp_endpoint_bh_rcv(struct work_struct *work)
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{
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struct sctp_endpoint *ep =
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container_of(work, struct sctp_endpoint,
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base.inqueue.immediate);
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struct sctp_association *asoc;
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struct sock *sk;
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struct net *net;
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struct sctp_transport *transport;
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struct sctp_chunk *chunk;
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struct sctp_inq *inqueue;
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union sctp_subtype subtype;
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enum sctp_state state;
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int error = 0;
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int first_time = 1; /* is this the first time through the loop */
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if (ep->base.dead)
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return;
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asoc = NULL;
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inqueue = &ep->base.inqueue;
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sk = ep->base.sk;
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net = sock_net(sk);
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while (NULL != (chunk = sctp_inq_pop(inqueue))) {
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subtype = SCTP_ST_CHUNK(chunk->chunk_hdr->type);
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/* If the first chunk in the packet is AUTH, do special
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* processing specified in Section 6.3 of SCTP-AUTH spec
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*/
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if (first_time && (subtype.chunk == SCTP_CID_AUTH)) {
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struct sctp_chunkhdr *next_hdr;
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next_hdr = sctp_inq_peek(inqueue);
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if (!next_hdr)
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goto normal;
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/* If the next chunk is COOKIE-ECHO, skip the AUTH
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* chunk while saving a pointer to it so we can do
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* Authentication later (during cookie-echo
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* processing).
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*/
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if (next_hdr->type == SCTP_CID_COOKIE_ECHO) {
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chunk->auth_chunk = skb_clone(chunk->skb,
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GFP_ATOMIC);
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chunk->auth = 1;
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continue;
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}
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}
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normal:
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/* We might have grown an association since last we
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* looked, so try again.
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*
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* This happens when we've just processed our
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* COOKIE-ECHO chunk.
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*/
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if (NULL == chunk->asoc) {
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asoc = sctp_endpoint_lookup_assoc(ep,
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sctp_source(chunk),
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&transport);
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chunk->asoc = asoc;
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chunk->transport = transport;
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}
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state = asoc ? asoc->state : SCTP_STATE_CLOSED;
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if (sctp_auth_recv_cid(subtype.chunk, asoc) && !chunk->auth)
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continue;
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/* Remember where the last DATA chunk came from so we
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* know where to send the SACK.
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*/
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if (asoc && sctp_chunk_is_data(chunk))
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asoc->peer.last_data_from = chunk->transport;
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else {
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SCTP_INC_STATS(ep->base.net, SCTP_MIB_INCTRLCHUNKS);
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if (asoc)
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asoc->stats.ictrlchunks++;
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}
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if (chunk->transport)
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chunk->transport->last_time_heard = ktime_get();
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error = sctp_do_sm(net, SCTP_EVENT_T_CHUNK, subtype, state,
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ep, asoc, chunk, GFP_ATOMIC);
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if (error && chunk)
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chunk->pdiscard = 1;
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/* Check to see if the endpoint is freed in response to
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* the incoming chunk. If so, get out of the while loop.
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*/
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if (!sctp_sk(sk)->ep)
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break;
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if (first_time)
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first_time = 0;
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}
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}
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