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    Subject[PATCH 4.4 18/75] net: add READ_ONCE() annotation in __skb_wait_for_more_packets()
    Date
    From: Eric Dumazet <edumazet@google.com>

    [ Upstream commit 7c422d0ce97552dde4a97e6290de70ec6efb0fc6 ]

    __skb_wait_for_more_packets() can be called while other cpus
    can feed packets to the socket receive queue.

    KCSAN reported :

    BUG: KCSAN: data-race in __skb_wait_for_more_packets / __udp_enqueue_schedule_skb

    write to 0xffff888102e40b58 of 8 bytes by interrupt on cpu 0:
    __skb_insert include/linux/skbuff.h:1852 [inline]
    __skb_queue_before include/linux/skbuff.h:1958 [inline]
    __skb_queue_tail include/linux/skbuff.h:1991 [inline]
    __udp_enqueue_schedule_skb+0x2d7/0x410 net/ipv4/udp.c:1470
    __udp_queue_rcv_skb net/ipv4/udp.c:1940 [inline]
    udp_queue_rcv_one_skb+0x7bd/0xc70 net/ipv4/udp.c:2057
    udp_queue_rcv_skb+0xb5/0x400 net/ipv4/udp.c:2074
    udp_unicast_rcv_skb.isra.0+0x7e/0x1c0 net/ipv4/udp.c:2233
    __udp4_lib_rcv+0xa44/0x17c0 net/ipv4/udp.c:2300
    udp_rcv+0x2b/0x40 net/ipv4/udp.c:2470
    ip_protocol_deliver_rcu+0x4d/0x420 net/ipv4/ip_input.c:204
    ip_local_deliver_finish+0x110/0x140 net/ipv4/ip_input.c:231
    NF_HOOK include/linux/netfilter.h:305 [inline]
    NF_HOOK include/linux/netfilter.h:299 [inline]
    ip_local_deliver+0x133/0x210 net/ipv4/ip_input.c:252
    dst_input include/net/dst.h:442 [inline]
    ip_rcv_finish+0x121/0x160 net/ipv4/ip_input.c:413
    NF_HOOK include/linux/netfilter.h:305 [inline]
    NF_HOOK include/linux/netfilter.h:299 [inline]
    ip_rcv+0x18f/0x1a0 net/ipv4/ip_input.c:523
    __netif_receive_skb_one_core+0xa7/0xe0 net/core/dev.c:5010
    __netif_receive_skb+0x37/0xf0 net/core/dev.c:5124
    process_backlog+0x1d3/0x420 net/core/dev.c:5955

    read to 0xffff888102e40b58 of 8 bytes by task 13035 on cpu 1:
    __skb_wait_for_more_packets+0xfa/0x320 net/core/datagram.c:100
    __skb_recv_udp+0x374/0x500 net/ipv4/udp.c:1683
    udp_recvmsg+0xe1/0xb10 net/ipv4/udp.c:1712
    inet_recvmsg+0xbb/0x250 net/ipv4/af_inet.c:838
    sock_recvmsg_nosec+0x5c/0x70 net/socket.c:871
    ___sys_recvmsg+0x1a0/0x3e0 net/socket.c:2480
    do_recvmmsg+0x19a/0x5c0 net/socket.c:2601
    __sys_recvmmsg+0x1ef/0x200 net/socket.c:2680
    __do_sys_recvmmsg net/socket.c:2703 [inline]
    __se_sys_recvmmsg net/socket.c:2696 [inline]
    __x64_sys_recvmmsg+0x89/0xb0 net/socket.c:2696
    do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
    entry_SYSCALL_64_after_hwframe+0x44/0xa9

    Reported by Kernel Concurrency Sanitizer on:
    CPU: 1 PID: 13035 Comm: syz-executor.3 Not tainted 5.4.0-rc3+ #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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/core/datagram.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/net/core/datagram.c
    +++ b/net/core/datagram.c
    @@ -96,7 +96,7 @@ static int wait_for_more_packets(struct
    if (error)
    goto out_err;

    - if (sk->sk_receive_queue.prev != skb)
    + if (READ_ONCE(sk->sk_receive_queue.prev) != skb)
    goto out;

    /* Socket shut down? */

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