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    Subject[PATCH AUTOSEL 5.6 228/606] tipc: block BH before using dst_cache
    Date
    From: Eric Dumazet <edumazet@google.com>

    [ Upstream commit 1378817486d6860f6a927f573491afe65287abf1 ]

    dst_cache_get() documents it must be used with BH disabled.

    sysbot reported :

    BUG: using smp_processor_id() in preemptible [00000000] code: /21697
    caller is dst_cache_get+0x3a/0xb0 net/core/dst_cache.c:68
    CPU: 0 PID: 21697 Comm: Not tainted 5.7.0-rc6-syzkaller #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    Call Trace:
    __dump_stack lib/dump_stack.c:77 [inline]
    dump_stack+0x188/0x20d lib/dump_stack.c:118
    check_preemption_disabled lib/smp_processor_id.c:47 [inline]
    debug_smp_processor_id.cold+0x88/0x9b lib/smp_processor_id.c:57
    dst_cache_get+0x3a/0xb0 net/core/dst_cache.c:68
    tipc_udp_xmit.isra.0+0xb9/0xad0 net/tipc/udp_media.c:164
    tipc_udp_send_msg+0x3e6/0x490 net/tipc/udp_media.c:244
    tipc_bearer_xmit_skb+0x1de/0x3f0 net/tipc/bearer.c:526
    tipc_enable_bearer+0xb2f/0xd60 net/tipc/bearer.c:331
    __tipc_nl_bearer_enable+0x2bf/0x390 net/tipc/bearer.c:995
    tipc_nl_bearer_enable+0x1e/0x30 net/tipc/bearer.c:1003
    genl_family_rcv_msg_doit net/netlink/genetlink.c:673 [inline]
    genl_family_rcv_msg net/netlink/genetlink.c:718 [inline]
    genl_rcv_msg+0x627/0xdf0 net/netlink/genetlink.c:735
    netlink_rcv_skb+0x15a/0x410 net/netlink/af_netlink.c:2469
    genl_rcv+0x24/0x40 net/netlink/genetlink.c:746
    netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
    netlink_unicast+0x537/0x740 net/netlink/af_netlink.c:1329
    netlink_sendmsg+0x882/0xe10 net/netlink/af_netlink.c:1918
    sock_sendmsg_nosec net/socket.c:652 [inline]
    sock_sendmsg+0xcf/0x120 net/socket.c:672
    ____sys_sendmsg+0x6bf/0x7e0 net/socket.c:2362
    ___sys_sendmsg+0x100/0x170 net/socket.c:2416
    __sys_sendmsg+0xec/0x1b0 net/socket.c:2449
    do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
    entry_SYSCALL_64_after_hwframe+0x49/0xb3
    RIP: 0033:0x45ca29

    Fixes: e9c1a793210f ("tipc: add dst_cache support for udp media")
    Cc: Xin Long <lucien.xin@gmail.com>
    Cc: Jon Maloy <jon.maloy@ericsson.com>
    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/tipc/udp_media.c | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    diff --git a/net/tipc/udp_media.c b/net/tipc/udp_media.c
    index d6620ad53546..28a283f26a8d 100644
    --- a/net/tipc/udp_media.c
    +++ b/net/tipc/udp_media.c
    @@ -161,9 +161,11 @@ static int tipc_udp_xmit(struct net *net, struct sk_buff *skb,
    struct udp_bearer *ub, struct udp_media_addr *src,
    struct udp_media_addr *dst, struct dst_cache *cache)
    {
    - struct dst_entry *ndst = dst_cache_get(cache);
    + struct dst_entry *ndst;
    int ttl, err = 0;

    + local_bh_disable();
    + ndst = dst_cache_get(cache);
    if (dst->proto == htons(ETH_P_IP)) {
    struct rtable *rt = (struct rtable *)ndst;

    @@ -210,9 +212,11 @@ static int tipc_udp_xmit(struct net *net, struct sk_buff *skb,
    src->port, dst->port, false);
    #endif
    }
    + local_bh_enable();
    return err;

    tx_error:
    + local_bh_enable();
    kfree_skb(skb);
    return err;
    }
    --
    2.25.1
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