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    Subject[PATCH 5.10 125/125] udp: annotate data races around unix_sk(sk)->gso_size
    Date
    From: Eric Dumazet <edumazet@google.com>

    commit 18a419bad63b7f68a1979e28459782518e7b6bbe upstream.

    Accesses to unix_sk(sk)->gso_size are lockless.
    Add READ_ONCE()/WRITE_ONCE() around them.

    BUG: KCSAN: data-race in udp_lib_setsockopt / udpv6_sendmsg

    write to 0xffff88812d78f47c of 2 bytes by task 10849 on cpu 1:
    udp_lib_setsockopt+0x3b3/0x710 net/ipv4/udp.c:2696
    udpv6_setsockopt+0x63/0x90 net/ipv6/udp.c:1630
    sock_common_setsockopt+0x5d/0x70 net/core/sock.c:3265
    __sys_setsockopt+0x18f/0x200 net/socket.c:2104
    __do_sys_setsockopt net/socket.c:2115 [inline]
    __se_sys_setsockopt net/socket.c:2112 [inline]
    __x64_sys_setsockopt+0x62/0x70 net/socket.c:2112
    do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
    entry_SYSCALL_64_after_hwframe+0x44/0xae

    read to 0xffff88812d78f47c of 2 bytes by task 10852 on cpu 0:
    udpv6_sendmsg+0x161/0x16b0 net/ipv6/udp.c:1299
    inet6_sendmsg+0x5f/0x80 net/ipv6/af_inet6.c:642
    sock_sendmsg_nosec net/socket.c:654 [inline]
    sock_sendmsg net/socket.c:674 [inline]
    ____sys_sendmsg+0x360/0x4d0 net/socket.c:2337
    ___sys_sendmsg net/socket.c:2391 [inline]
    __sys_sendmmsg+0x315/0x4b0 net/socket.c:2477
    __do_sys_sendmmsg net/socket.c:2506 [inline]
    __se_sys_sendmmsg net/socket.c:2503 [inline]
    __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2503
    do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
    entry_SYSCALL_64_after_hwframe+0x44/0xae

    value changed: 0x0000 -> 0x0005

    Reported by Kernel Concurrency Sanitizer on:
    CPU: 0 PID: 10852 Comm: syz-executor.0 Not tainted 5.13.0-syzkaller #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

    Fixes: bec1f6f69736 ("udp: generate gso with UDP_SEGMENT")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Cc: Willem de Bruijn <willemb@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/ipv4/udp.c | 6 +++---
    net/ipv6/udp.c | 2 +-
    2 files changed, 4 insertions(+), 4 deletions(-)

    --- a/net/ipv4/udp.c
    +++ b/net/ipv4/udp.c
    @@ -1097,7 +1097,7 @@ int udp_sendmsg(struct sock *sk, struct
    }

    ipcm_init_sk(&ipc, inet);
    - ipc.gso_size = up->gso_size;
    + ipc.gso_size = READ_ONCE(up->gso_size);

    if (msg->msg_controllen) {
    err = udp_cmsg_send(sk, msg, &ipc.gso_size);
    @@ -2655,7 +2655,7 @@ int udp_lib_setsockopt(struct sock *sk,
    case UDP_SEGMENT:
    if (val < 0 || val > USHRT_MAX)
    return -EINVAL;
    - up->gso_size = val;
    + WRITE_ONCE(up->gso_size, val);
    break;

    case UDP_GRO:
    @@ -2750,7 +2750,7 @@ int udp_lib_getsockopt(struct sock *sk,
    break;

    case UDP_SEGMENT:
    - val = up->gso_size;
    + val = READ_ONCE(up->gso_size);
    break;

    case UDP_GRO:
    --- a/net/ipv6/udp.c
    +++ b/net/ipv6/udp.c
    @@ -1294,7 +1294,7 @@ int udpv6_sendmsg(struct sock *sk, struc
    int (*getfrag)(void *, char *, int, int, int, struct sk_buff *);

    ipcm6_init(&ipc6);
    - ipc6.gso_size = up->gso_size;
    + ipc6.gso_size = READ_ONCE(up->gso_size);
    ipc6.sockc.tsflags = sk->sk_tsflags;
    ipc6.sockc.mark = sk->sk_mark;


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