tcp/dccp: fix ireq->opt races

syzkaller found another bug in DCCP/TCP stacks [1]

For the reasons explained in commit ce1050089c96 ("tcp/dccp: fix
ireq->pktopts race"), we need to make sure we do not access
ireq->opt unless we own the request sock.

Note the opt field is renamed to ireq_opt to ease grep games.

[1]
BUG: KASAN: use-after-free in ip_queue_xmit+0x1687/0x18e0 net/ipv4/ip_output.c:474
Read of size 1 at addr ffff8801c951039c by task syz-executor5/3295

CPU: 1 PID: 3295 Comm: syz-executor5 Not tainted 4.14.0-rc4+ #80
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:52
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:427
 ip_queue_xmit+0x1687/0x18e0 net/ipv4/ip_output.c:474
 tcp_transmit_skb+0x1ab7/0x3840 net/ipv4/tcp_output.c:1135
 tcp_send_ack.part.37+0x3bb/0x650 net/ipv4/tcp_output.c:3587
 tcp_send_ack+0x49/0x60 net/ipv4/tcp_output.c:3557
 __tcp_ack_snd_check+0x2c6/0x4b0 net/ipv4/tcp_input.c:5072
 tcp_ack_snd_check net/ipv4/tcp_input.c:5085 [inline]
 tcp_rcv_state_process+0x2eff/0x4850 net/ipv4/tcp_input.c:6071
 tcp_child_process+0x342/0x990 net/ipv4/tcp_minisocks.c:816
 tcp_v4_rcv+0x1827/0x2f80 net/ipv4/tcp_ipv4.c:1682
 ip_local_deliver_finish+0x2e2/0xba0 net/ipv4/ip_input.c:216
 NF_HOOK include/linux/netfilter.h:249 [inline]
 ip_local_deliver+0x1ce/0x6e0 net/ipv4/ip_input.c:257
 dst_input include/net/dst.h:464 [inline]
 ip_rcv_finish+0x887/0x19a0 net/ipv4/ip_input.c:397
 NF_HOOK include/linux/netfilter.h:249 [inline]
 ip_rcv+0xc3f/0x1820 net/ipv4/ip_input.c:493
 __netif_receive_skb_core+0x1a3e/0x34b0 net/core/dev.c:4476
 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4514
 netif_receive_skb_internal+0x10b/0x670 net/core/dev.c:4587
 netif_receive_skb+0xae/0x390 net/core/dev.c:4611
 tun_rx_batched.isra.50+0x5ed/0x860 drivers/net/tun.c:1372
 tun_get_user+0x249c/0x36d0 drivers/net/tun.c:1766
 tun_chr_write_iter+0xbf/0x160 drivers/net/tun.c:1792
 call_write_iter include/linux/fs.h:1770 [inline]
 new_sync_write fs/read_write.c:468 [inline]
 __vfs_write+0x68a/0x970 fs/read_write.c:481
 vfs_write+0x18f/0x510 fs/read_write.c:543
 SYSC_write fs/read_write.c:588 [inline]
 SyS_write+0xef/0x220 fs/read_write.c:580
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x40c341
RSP: 002b:00007f469523ec10 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000718000 RCX: 000000000040c341
RDX: 0000000000000037 RSI: 0000000020004000 RDI: 0000000000000015
RBP: 0000000000000086 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000000f4240 R11: 0000000000000293 R12: 00000000004b7fd1
R13: 00000000ffffffff R14: 0000000020000000 R15: 0000000000025000

Allocated by task 3295:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
 __do_kmalloc mm/slab.c:3725 [inline]
 __kmalloc+0x162/0x760 mm/slab.c:3734
 kmalloc include/linux/slab.h:498 [inline]
 tcp_v4_save_options include/net/tcp.h:1962 [inline]
 tcp_v4_init_req+0x2d3/0x3e0 net/ipv4/tcp_ipv4.c:1271
 tcp_conn_request+0xf6d/0x3410 net/ipv4/tcp_input.c:6283
 tcp_v4_conn_request+0x157/0x210 net/ipv4/tcp_ipv4.c:1313
 tcp_rcv_state_process+0x8ea/0x4850 net/ipv4/tcp_input.c:5857
 tcp_v4_do_rcv+0x55c/0x7d0 net/ipv4/tcp_ipv4.c:1482
 tcp_v4_rcv+0x2d10/0x2f80 net/ipv4/tcp_ipv4.c:1711
 ip_local_deliver_finish+0x2e2/0xba0 net/ipv4/ip_input.c:216
 NF_HOOK include/linux/netfilter.h:249 [inline]
 ip_local_deliver+0x1ce/0x6e0 net/ipv4/ip_input.c:257
 dst_input include/net/dst.h:464 [inline]
 ip_rcv_finish+0x887/0x19a0 net/ipv4/ip_input.c:397
 NF_HOOK include/linux/netfilter.h:249 [inline]
 ip_rcv+0xc3f/0x1820 net/ipv4/ip_input.c:493
 __netif_receive_skb_core+0x1a3e/0x34b0 net/core/dev.c:4476
 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4514
 netif_receive_skb_internal+0x10b/0x670 net/core/dev.c:4587
 netif_receive_skb+0xae/0x390 net/core/dev.c:4611
 tun_rx_batched.isra.50+0x5ed/0x860 drivers/net/tun.c:1372
 tun_get_user+0x249c/0x36d0 drivers/net/tun.c:1766
 tun_chr_write_iter+0xbf/0x160 drivers/net/tun.c:1792
 call_write_iter include/linux/fs.h:1770 [inline]
 new_sync_write fs/read_write.c:468 [inline]
 __vfs_write+0x68a/0x970 fs/read_write.c:481
 vfs_write+0x18f/0x510 fs/read_write.c:543
 SYSC_write fs/read_write.c:588 [inline]
 SyS_write+0xef/0x220 fs/read_write.c:580
 entry_SYSCALL_64_fastpath+0x1f/0xbe

Freed by task 3306:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3503 [inline]
 kfree+0xca/0x250 mm/slab.c:3820
 inet_sock_destruct+0x59d/0x950 net/ipv4/af_inet.c:157
 __sk_destruct+0xfd/0x910 net/core/sock.c:1560
 sk_destruct+0x47/0x80 net/core/sock.c:1595
 __sk_free+0x57/0x230 net/core/sock.c:1603
 sk_free+0x2a/0x40 net/core/sock.c:1614
 sock_put include/net/sock.h:1652 [inline]
 inet_csk_complete_hashdance+0xd5/0xf0 net/ipv4/inet_connection_sock.c:959
 tcp_check_req+0xf4d/0x1620 net/ipv4/tcp_minisocks.c:765
 tcp_v4_rcv+0x17f6/0x2f80 net/ipv4/tcp_ipv4.c:1675
 ip_local_deliver_finish+0x2e2/0xba0 net/ipv4/ip_input.c:216
 NF_HOOK include/linux/netfilter.h:249 [inline]
 ip_local_deliver+0x1ce/0x6e0 net/ipv4/ip_input.c:257
 dst_input include/net/dst.h:464 [inline]
 ip_rcv_finish+0x887/0x19a0 net/ipv4/ip_input.c:397
 NF_HOOK include/linux/netfilter.h:249 [inline]
 ip_rcv+0xc3f/0x1820 net/ipv4/ip_input.c:493
 __netif_receive_skb_core+0x1a3e/0x34b0 net/core/dev.c:4476
 __netif_receive_skb+0x2c/0x1b0 net/core/dev.c:4514
 netif_receive_skb_internal+0x10b/0x670 net/core/dev.c:4587
 netif_receive_skb+0xae/0x390 net/core/dev.c:4611
 tun_rx_batched.isra.50+0x5ed/0x860 drivers/net/tun.c:1372
 tun_get_user+0x249c/0x36d0 drivers/net/tun.c:1766
 tun_chr_write_iter+0xbf/0x160 drivers/net/tun.c:1792
 call_write_iter include/linux/fs.h:1770 [inline]
 new_sync_write fs/read_write.c:468 [inline]
 __vfs_write+0x68a/0x970 fs/read_write.c:481
 vfs_write+0x18f/0x510 fs/read_write.c:543
 SYSC_write fs/read_write.c:588 [inline]
 SyS_write+0xef/0x220 fs/read_write.c:580
 entry_SYSCALL_64_fastpath+0x1f/0xbe

Fixes: e994b2f0fb92 ("tcp: do not lock listener to process SYN packets")
Fixes: 079096f103fa ("tcp/dccp: install syn_recv requests into ehash table")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
index aa95053dfc78d35d04aef276e2a5dce7343f72a0..425752f768d2f1a0efb13964204e07f27609e9db 100644 (file)
--- a/include/net/inet_sock.h
+++ b/include/net/inet_sock.h
@@ -96,7 +96,7 @@ struct inet_request_sock {
        kmemcheck_bitfield_end(flags);
        u32                     ir_mark;
        union {
-               struct ip_options_rcu   *opt;
+               struct ip_options_rcu __rcu     *ireq_opt;
 #if IS_ENABLED(CONFIG_IPV6)
                struct {
                        struct ipv6_txoptions   *ipv6_opt;

diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 001c08696334bba0ceb896c116e595b814af0667..0490916864f93d5466e87f5b97dc524b3ee57a2e 100644 (file)
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -414,8 +414,7 @@ struct sock *dccp_v4_request_recv_sock(const struct sock *sk,
        sk_daddr_set(newsk, ireq->ir_rmt_addr);
        sk_rcv_saddr_set(newsk, ireq->ir_loc_addr);
        newinet->inet_saddr     = ireq->ir_loc_addr;
-       newinet->inet_opt       = ireq->opt;
-       ireq->opt          = NULL;
+       RCU_INIT_POINTER(newinet->inet_opt, rcu_dereference(ireq->ireq_opt));
        newinet->mc_index  = inet_iif(skb);
        newinet->mc_ttl    = ip_hdr(skb)->ttl;
        newinet->inet_id   = jiffies;
@@ -430,7 +429,10 @@ struct sock *dccp_v4_request_recv_sock(const struct sock *sk,
        if (__inet_inherit_port(sk, newsk) < 0)
                goto put_and_exit;
        *own_req = inet_ehash_nolisten(newsk, req_to_sk(req_unhash));
-
+       if (*own_req)
+               ireq->ireq_opt = NULL;
+       else
+               newinet->inet_opt = NULL;
        return newsk;
 
 exit_overflow:
@@ -441,6 +443,7 @@ exit:
        __NET_INC_STATS(sock_net(sk), LINUX_MIB_LISTENDROPS);
        return NULL;
 put_and_exit:
+       newinet->inet_opt = NULL;
        inet_csk_prepare_forced_close(newsk);
        dccp_done(newsk);
        goto exit;
@@ -492,7 +495,7 @@ static int dccp_v4_send_response(const struct sock *sk, struct request_sock *req
                                                              ireq->ir_rmt_addr);
                err = ip_build_and_send_pkt(skb, sk, ireq->ir_loc_addr,
                                            ireq->ir_rmt_addr,
-                                           ireq->opt);
+                                           rcu_dereference(ireq->ireq_opt));
                err = net_xmit_eval(err);
        }
 
@@ -548,7 +551,7 @@ out:
 static void dccp_v4_reqsk_destructor(struct request_sock *req)
 {
        dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
-       kfree(inet_rsk(req)->opt);
+       kfree(rcu_dereference_protected(inet_rsk(req)->ireq_opt, 1));
 }
 
 void dccp_syn_ack_timeout(const struct request_sock *req)

diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
index 2ae8f54cb32148f2499f78ecbf29259db36bd207..82178cc69c9618bae69c096290a7a96a8b8bade0 100644 (file)
--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -1951,7 +1951,7 @@ int cipso_v4_req_setattr(struct request_sock *req,
        buf = NULL;
 
        req_inet = inet_rsk(req);
-       opt = xchg(&req_inet->opt, opt);
+       opt = xchg((__force struct ip_options_rcu **)&req_inet->ireq_opt, opt);
        if (opt)
                kfree_rcu(opt, rcu);
 
@@ -1973,11 +1973,13 @@ req_setattr_failure:
  * values on failure.
  *
  */
-static int cipso_v4_delopt(struct ip_options_rcu **opt_ptr)
+static int cipso_v4_delopt(struct ip_options_rcu __rcu **opt_ptr)
 {
+       struct ip_options_rcu *opt = rcu_dereference_protected(*opt_ptr, 1);
        int hdr_delta = 0;
-       struct ip_options_rcu *opt = *opt_ptr;
 
+       if (!opt || opt->opt.cipso == 0)
+               return 0;
        if (opt->opt.srr || opt->opt.rr || opt->opt.ts || opt->opt.router_alert) {
                u8 cipso_len;
                u8 cipso_off;
@@ -2039,14 +2041,10 @@ static int cipso_v4_delopt(struct ip_options_rcu **opt_ptr)
  */
 void cipso_v4_sock_delattr(struct sock *sk)
 {
-       int hdr_delta;
-       struct ip_options_rcu *opt;
        struct inet_sock *sk_inet;
+       int hdr_delta;
 
        sk_inet = inet_sk(sk);
-       opt = rcu_dereference_protected(sk_inet->inet_opt, 1);
-       if (!opt || opt->opt.cipso == 0)
-               return;
 
        hdr_delta = cipso_v4_delopt(&sk_inet->inet_opt);
        if (sk_inet->is_icsk && hdr_delta > 0) {
@@ -2066,15 +2064,7 @@ void cipso_v4_sock_delattr(struct sock *sk)
  */
 void cipso_v4_req_delattr(struct request_sock *req)
 {
-       struct ip_options_rcu *opt;
-       struct inet_request_sock *req_inet;
-
-       req_inet = inet_rsk(req);
-       opt = req_inet->opt;
-       if (!opt || opt->opt.cipso == 0)
-               return;
-
-       cipso_v4_delopt(&req_inet->opt);
+       cipso_v4_delopt(&inet_rsk(req)->ireq_opt);
 }
 
 /**

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 67aec7a106860b26c929fea1624d652c87972f04..5ec9136a7c36933cb36e5cd50058eb6cf189a7c3 100644 (file)
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -540,9 +540,10 @@ struct dst_entry *inet_csk_route_req(const struct sock *sk,
 {
        const struct inet_request_sock *ireq = inet_rsk(req);
        struct net *net = read_pnet(&ireq->ireq_net);
-       struct ip_options_rcu *opt = ireq->opt;
+       struct ip_options_rcu *opt;
        struct rtable *rt;
 
+       opt = rcu_dereference(ireq->ireq_opt);
        flowi4_init_output(fl4, ireq->ir_iif, ireq->ir_mark,
                           RT_CONN_FLAGS(sk), RT_SCOPE_UNIVERSE,
                           sk->sk_protocol, inet_sk_flowi_flags(sk),
@@ -576,10 +577,9 @@ struct dst_entry *inet_csk_route_child_sock(const struct sock *sk,
        struct flowi4 *fl4;
        struct rtable *rt;
 
+       opt = rcu_dereference(ireq->ireq_opt);
        fl4 = &newinet->cork.fl.u.ip4;
 
-       rcu_read_lock();
-       opt = rcu_dereference(newinet->inet_opt);
        flowi4_init_output(fl4, ireq->ir_iif, ireq->ir_mark,
                           RT_CONN_FLAGS(sk), RT_SCOPE_UNIVERSE,
                           sk->sk_protocol, inet_sk_flowi_flags(sk),
@@ -592,13 +592,11 @@ struct dst_entry *inet_csk_route_child_sock(const struct sock *sk,
                goto no_route;
        if (opt && opt->opt.is_strictroute && rt->rt_uses_gateway)
                goto route_err;
-       rcu_read_unlock();
        return &rt->dst;
 
 route_err:
        ip_rt_put(rt);
 no_route:
-       rcu_read_unlock();
        __IP_INC_STATS(net, IPSTATS_MIB_OUTNOROUTES);
        return NULL;
 }

diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index b1bb1b3a108232d56aa82383422d68b5ff9da3ed..77cf32a80952fcf3ceff4ada946cc2d0df2411d9 100644 (file)
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -355,7 +355,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
        /* We throwed the options of the initial SYN away, so we hope
         * the ACK carries the same options again (see RFC1122 4.2.3.8)
         */
-       ireq->opt = tcp_v4_save_options(sock_net(sk), skb);
+       RCU_INIT_POINTER(ireq->ireq_opt, tcp_v4_save_options(sock_net(sk), skb));
 
        if (security_inet_conn_request(sk, skb, req)) {
                reqsk_free(req);

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index c5d7656beeee29b3c92e1c8824dbf00d3fa32d28..7eec3383702bbab497a12095b55d255532ad5f60 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6196,7 +6196,7 @@ struct request_sock *inet_reqsk_alloc(const struct request_sock_ops *ops,
                struct inet_request_sock *ireq = inet_rsk(req);
 
                kmemcheck_annotate_bitfield(ireq, flags);
-               ireq->opt = NULL;
+               ireq->ireq_opt = NULL;
 #if IS_ENABLED(CONFIG_IPV6)
                ireq->pktopts = NULL;
 #endif

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 85164d4d3e537537c87d74c00172592c860d4dfb..4c43365c374c8bf868fc0b862333244ca26d5016 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -877,7 +877,7 @@ static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst,
 
                err = ip_build_and_send_pkt(skb, sk, ireq->ir_loc_addr,
                                            ireq->ir_rmt_addr,
-                                           ireq->opt);
+                                           rcu_dereference(ireq->ireq_opt));
                err = net_xmit_eval(err);
        }
 
@@ -889,7 +889,7 @@ static int tcp_v4_send_synack(const struct sock *sk, struct dst_entry *dst,
  */
 static void tcp_v4_reqsk_destructor(struct request_sock *req)
 {
-       kfree(inet_rsk(req)->opt);
+       kfree(rcu_dereference_protected(inet_rsk(req)->ireq_opt, 1));
 }
 
 #ifdef CONFIG_TCP_MD5SIG
@@ -1265,10 +1265,11 @@ static void tcp_v4_init_req(struct request_sock *req,
                            struct sk_buff *skb)
 {
        struct inet_request_sock *ireq = inet_rsk(req);
+       struct net *net = sock_net(sk_listener);
 
        sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
        sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
-       ireq->opt = tcp_v4_save_options(sock_net(sk_listener), skb);
+       RCU_INIT_POINTER(ireq->ireq_opt, tcp_v4_save_options(net, skb));
 }
 
 static struct dst_entry *tcp_v4_route_req(const struct sock *sk,
@@ -1355,10 +1356,9 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
        sk_daddr_set(newsk, ireq->ir_rmt_addr);
        sk_rcv_saddr_set(newsk, ireq->ir_loc_addr);
        newsk->sk_bound_dev_if = ireq->ir_iif;
-       newinet->inet_saddr           = ireq->ir_loc_addr;
-       inet_opt              = ireq->opt;
-       rcu_assign_pointer(newinet->inet_opt, inet_opt);
-       ireq->opt             = NULL;
+       newinet->inet_saddr   = ireq->ir_loc_addr;
+       inet_opt              = rcu_dereference(ireq->ireq_opt);
+       RCU_INIT_POINTER(newinet->inet_opt, inet_opt);
        newinet->mc_index     = inet_iif(skb);
        newinet->mc_ttl       = ip_hdr(skb)->ttl;
        newinet->rcv_tos      = ip_hdr(skb)->tos;
@@ -1403,9 +1403,12 @@ struct sock *tcp_v4_syn_recv_sock(const struct sock *sk, struct sk_buff *skb,
        if (__inet_inherit_port(sk, newsk) < 0)
                goto put_and_exit;
        *own_req = inet_ehash_nolisten(newsk, req_to_sk(req_unhash));
-       if (*own_req)
+       if (likely(*own_req)) {
                tcp_move_syn(newtp, req);
-
+               ireq->ireq_opt = NULL;
+       } else {
+               newinet->inet_opt = NULL;
+       }
        return newsk;
 
 exit_overflow:
@@ -1416,6 +1419,7 @@ exit:
        tcp_listendrop(sk);
        return NULL;
 put_and_exit:
+       newinet->inet_opt = NULL;
        inet_csk_prepare_forced_close(newsk);
        tcp_done(newsk);
        goto exit;