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    Subject[PATCH 4.4 065/266] tipc: handle the err returned from cmd header function
    Date
    From: Xin Long <lucien.xin@gmail.com>

    commit 2ac695d1d602ce00b12170242f58c3d3a8e36d04 upstream.

    Syzbot found a crash:

    BUG: KMSAN: uninit-value in tipc_nl_compat_name_table_dump+0x54f/0xcd0 net/tipc/netlink_compat.c:872
    Call Trace:
    tipc_nl_compat_name_table_dump+0x54f/0xcd0 net/tipc/netlink_compat.c:872
    __tipc_nl_compat_dumpit+0x59e/0xda0 net/tipc/netlink_compat.c:215
    tipc_nl_compat_dumpit+0x63a/0x820 net/tipc/netlink_compat.c:280
    tipc_nl_compat_handle net/tipc/netlink_compat.c:1226 [inline]
    tipc_nl_compat_recv+0x1b5f/0x2750 net/tipc/netlink_compat.c:1265
    genl_family_rcv_msg net/netlink/genetlink.c:601 [inline]
    genl_rcv_msg+0x185f/0x1a60 net/netlink/genetlink.c:626
    netlink_rcv_skb+0x431/0x620 net/netlink/af_netlink.c:2477
    genl_rcv+0x63/0x80 net/netlink/genetlink.c:637
    netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
    netlink_unicast+0xf3e/0x1020 net/netlink/af_netlink.c:1336
    netlink_sendmsg+0x127f/0x1300 net/netlink/af_netlink.c:1917
    sock_sendmsg_nosec net/socket.c:622 [inline]
    sock_sendmsg net/socket.c:632 [inline]

    Uninit was created at:
    __alloc_skb+0x309/0xa20 net/core/skbuff.c:208
    alloc_skb include/linux/skbuff.h:1012 [inline]
    netlink_alloc_large_skb net/netlink/af_netlink.c:1182 [inline]
    netlink_sendmsg+0xb82/0x1300 net/netlink/af_netlink.c:1892
    sock_sendmsg_nosec net/socket.c:622 [inline]
    sock_sendmsg net/socket.c:632 [inline]

    It was supposed to be fixed on commit 974cb0e3e7c9 ("tipc: fix uninit-value
    in tipc_nl_compat_name_table_dump") by checking TLV_GET_DATA_LEN(msg->req)
    in cmd->header()/tipc_nl_compat_name_table_dump_header(), which is called
    ahead of tipc_nl_compat_name_table_dump().

    However, tipc_nl_compat_dumpit() doesn't handle the error returned from cmd
    header function. It means even when the check added in that fix fails, it
    won't stop calling tipc_nl_compat_name_table_dump(), and the issue will be
    triggered again.

    So this patch is to add the process for the err returned from cmd header
    function in tipc_nl_compat_dumpit().

    Reported-by: syzbot+3ce8520484b0d4e260a5@syzkaller.appspotmail.com
    Signed-off-by: Xin Long <lucien.xin@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    net/tipc/netlink_compat.c | 10 ++++++++--
    1 file changed, 8 insertions(+), 2 deletions(-)

    --- a/net/tipc/netlink_compat.c
    +++ b/net/tipc/netlink_compat.c
    @@ -262,8 +262,14 @@ static int tipc_nl_compat_dumpit(struct
    if (msg->rep_type)
    tipc_tlv_init(msg->rep, msg->rep_type);

    - if (cmd->header)
    - (*cmd->header)(msg);
    + if (cmd->header) {
    + err = (*cmd->header)(msg);
    + if (err) {
    + kfree_skb(msg->rep);
    + msg->rep = NULL;
    + return err;
    + }
    + }

    arg = nlmsg_new(0, GFP_KERNEL);
    if (!arg) {

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