• Xin Long's avatar
    sctp: avoid running the sctp state machine recursively · a5d00345
    Xin Long authored
    [ Upstream commit fbd019737d71e405f86549fd738f81e2ff3dd073 ]
    
    Ying triggered a call trace when doing an asconf testing:
    
      BUG: scheduling while atomic: swapper/12/0/0x10000100
      Call Trace:
       <IRQ>  [<ffffffffa4375904>] dump_stack+0x19/0x1b
       [<ffffffffa436fcaf>] __schedule_bug+0x64/0x72
       [<ffffffffa437b93a>] __schedule+0x9ba/0xa00
       [<ffffffffa3cd5326>] __cond_resched+0x26/0x30
       [<ffffffffa437bc4a>] _cond_resched+0x3a/0x50
       [<ffffffffa3e22be8>] kmem_cache_alloc_node+0x38/0x200
       [<ffffffffa423512d>] __alloc_skb+0x5d/0x2d0
       [<ffffffffc0995320>] sctp_packet_transmit+0x610/0xa20 [sctp]
       [<ffffffffc098510e>] sctp_outq_flush+0x2ce/0xc00 [sctp]
       [<ffffffffc098646c>] sctp_outq_uncork+0x1c/0x20 [sctp]
       [<ffffffffc0977338>] sctp_cmd_interpreter.isra.22+0xc8/0x1460 [sctp]
       [<ffffffffc0976ad1>] sctp_do_sm+0xe1/0x350 [sctp]
       [<ffffffffc099443d>] sctp_primitive_ASCONF+0x3d/0x50 [sctp]
       [<ffffffffc0977384>] sctp_cmd_interpreter.isra.22+0x114/0x1460 [sctp]
       [<ffffffffc0976ad1>] sctp_do_sm+0xe1/0x350 [sctp]
       [<ffffffffc097b3a4>] sctp_assoc_bh_rcv+0xf4/0x1b0 [sctp]
       [<ffffffffc09840f1>] sctp_inq_push+0x51/0x70 [sctp]
       [<ffffffffc099732b>] sctp_rcv+0xa8b/0xbd0 [sctp]
    
    As it shows, the first sctp_do_sm() running under atomic context (NET_RX
    softirq) invoked sctp_primitive_ASCONF() that uses GFP_KERNEL flag later,
    and this flag is supposed to be used in non-atomic context only. Besides,
    sctp_do_sm() was called recursively, which is not expected.
    
    Vlad tried to fix this recursive call in Commit c0786693 ("sctp: Fix
    oops when sending queued ASCONF chunks") by introducing a new command
    SCTP_CMD_SEND_NEXT_ASCONF. But it didn't work as this command is still
    used in the first sctp_do_sm() call, and sctp_primitive_ASCONF() will
    be called in this command again.
    
    To avoid calling sctp_do_sm() recursively, we send the next queued ASCONF
    not by sctp_primitive_ASCONF(), but by sctp_sf_do_prm_asconf() in the 1st
    sctp_do_sm() directly.
    Reported-by: default avatarYing Xu <yinxu@redhat.com>
    Signed-off-by: default avatarXin Long <lucien.xin@gmail.com>
    Acked-by: default avatarNeil Horman <nhorman@tuxdriver.com>
    Acked-by: default avatarMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    a5d00345