net/packet: annotate accesses to po->ifindex

Like prior patch, we need to annotate lockless accesses to po->ifindex
For instance, packet_getname() is reading po->ifindex (twice) while
another thread is able to change po->ifindex.

KCSAN reported:

BUG: KCSAN: data-race in packet_do_bind / packet_getname

write to 0xffff888143ce3cbc of 4 bytes by task 25573 on cpu 1:
 packet_do_bind+0x420/0x7e0 net/packet/af_packet.c:3191
 packet_bind+0xc3/0xd0 net/packet/af_packet.c:3255
 __sys_bind+0x200/0x290 net/socket.c:1637
 __do_sys_bind net/socket.c:1648 [inline]
 __se_sys_bind net/socket.c:1646 [inline]
 __x64_sys_bind+0x3d/0x50 net/socket.c:1646
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888143ce3cbc of 4 bytes by task 25578 on cpu 0:
 packet_getname+0x5b/0x1a0 net/packet/af_packet.c:3525
 __sys_getsockname+0x10e/0x1a0 net/socket.c:1887
 __do_sys_getsockname net/socket.c:1902 [inline]
 __se_sys_getsockname net/socket.c:1899 [inline]
 __x64_sys_getsockname+0x3e/0x50 net/socket.c:1899
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 25578 Comm: syz-executor.5 Not tainted 5.13.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index e91a36bdd1abaf18a679b914ae0d722d42c9369b..330ba68828e7dbabf4d4d6b76e7cb664253c432e 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -3187,11 +3187,11 @@ static int packet_do_bind(struct sock *sk, const char *name, int ifindex,
                if (unlikely(unlisted)) {
                        dev_put(dev);
                        po->prot_hook.dev = NULL;
-                       po->ifindex = -1;
+                       WRITE_ONCE(po->ifindex, -1);
                        packet_cached_dev_reset(po);
                } else {
                        po->prot_hook.dev = dev;
-                       po->ifindex = dev ? dev->ifindex : 0;
+                       WRITE_ONCE(po->ifindex, dev ? dev->ifindex : 0);
                        packet_cached_dev_assign(po, dev);
                }
        }
@@ -3505,7 +3505,7 @@ static int packet_getname_spkt(struct socket *sock, struct sockaddr *uaddr,
        uaddr->sa_family = AF_PACKET;
        memset(uaddr->sa_data, 0, sizeof(uaddr->sa_data));
        rcu_read_lock();
-       dev = dev_get_by_index_rcu(sock_net(sk), pkt_sk(sk)->ifindex);
+       dev = dev_get_by_index_rcu(sock_net(sk), READ_ONCE(pkt_sk(sk)->ifindex));
        if (dev)
                strlcpy(uaddr->sa_data, dev->name, sizeof(uaddr->sa_data));
        rcu_read_unlock();
@@ -3520,16 +3520,18 @@ static int packet_getname(struct socket *sock, struct sockaddr *uaddr,
        struct sock *sk = sock->sk;
        struct packet_sock *po = pkt_sk(sk);
        DECLARE_SOCKADDR(struct sockaddr_ll *, sll, uaddr);
+       int ifindex;
 
        if (peer)
                return -EOPNOTSUPP;
 
+       ifindex = READ_ONCE(po->ifindex);
        sll->sll_family = AF_PACKET;
-       sll->sll_ifindex = po->ifindex;
+       sll->sll_ifindex = ifindex;
        sll->sll_protocol = READ_ONCE(po->num);
        sll->sll_pkttype = 0;
        rcu_read_lock();
-       dev = dev_get_by_index_rcu(sock_net(sk), po->ifindex);
+       dev = dev_get_by_index_rcu(sock_net(sk), ifindex);
        if (dev) {
                sll->sll_hatype = dev->type;
                sll->sll_halen = dev->addr_len;
@@ -4108,7 +4110,7 @@ static int packet_notifier(struct notifier_block *this,
                                }
                                if (msg == NETDEV_UNREGISTER) {
                                        packet_cached_dev_reset(po);
-                                       po->ifindex = -1;
+                                       WRITE_ONCE(po->ifindex, -1);
                                        if (po->prot_hook.dev)
                                                dev_put(po->prot_hook.dev);
                                        po->prot_hook.dev = NULL;
@@ -4620,7 +4622,7 @@ static int packet_seq_show(struct seq_file *seq, void *v)
                           refcount_read(&s->sk_refcnt),
                           s->sk_type,
                           ntohs(READ_ONCE(po->num)),
-                          po->ifindex,
+                          READ_ONCE(po->ifindex),
                           po->running,
                           atomic_read(&s->sk_rmem_alloc),
                           from_kuid_munged(seq_user_ns(seq), sock_i_uid(s)),