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    Subject[v2.6.34-stable 65/77] SCTP: fix race between sctp_bind_addr_free() and sctp_bind_addr_conflict()
    From: Jacek Luczak <>

    This is a commit scheduled for the next v2.6.34 longterm release.
    If you see a problem with using this for longterm, please comment.

    commit c182f90bc1f22ce5039b8722e45621d5f96862c2 upstream.

    During the sctp_close() call, we do not use rcu primitives to
    destroy the address list attached to the endpoint. At the same
    time, we do the removal of addresses from this list before
    attempting to remove the socket from the port hash

    As a result, it is possible for another process to find the socket
    in the port hash that is in the process of being closed. It then
    proceeds to traverse the address list to find the conflict, only
    to have that address list suddenly disappear without rcu() critical

    Fix issue by closing address list removal inside RCU critical

    Race can result in a kernel crash with general protection fault or
    kernel NULL pointer dereference:

    kernel: general protection fault: 0000 [#1] SMP
    kernel: RIP: 0010:[<ffffffffa02f3dde>] [<ffffffffa02f3dde>] sctp_bind_addr_conflict+0x64/0x82 [sctp]
    kernel: Call Trace:
    kernel: [<ffffffffa02f415f>] ? sctp_get_port_local+0x17b/0x2a3 [sctp]
    kernel: [<ffffffffa02f3d45>] ? sctp_bind_addr_match+0x33/0x68 [sctp]
    kernel: [<ffffffffa02f4416>] ? sctp_do_bind+0xd3/0x141 [sctp]
    kernel: [<ffffffffa02f5030>] ? sctp_bindx_add+0x4d/0x8e [sctp]
    kernel: [<ffffffffa02f5183>] ? sctp_setsockopt_bindx+0x112/0x4a4 [sctp]
    kernel: [<ffffffff81089e82>] ? generic_file_aio_write+0x7f/0x9b
    kernel: [<ffffffffa02f763e>] ? sctp_setsockopt+0x14f/0xfee [sctp]
    kernel: [<ffffffff810c11fb>] ? do_sync_write+0xab/0xeb
    kernel: [<ffffffff810e82ab>] ? fsnotify+0x239/0x282
    kernel: [<ffffffff810c2462>] ? alloc_file+0x18/0xb1
    kernel: [<ffffffff8134a0b1>] ? compat_sys_setsockopt+0x1a5/0x1d9
    kernel: [<ffffffff8134aaf1>] ? compat_sys_socketcall+0x143/0x1a4
    kernel: [<ffffffff810467dc>] ? sysenter_dispatch+0x7/0x32

    Signed-off-by: Jacek Luczak <>
    Acked-by: Vlad Yasevich <>
    CC: Eric Dumazet <>
    Reviewed-by: Eric Dumazet <>
    Signed-off-by: David S. Miller <>
    Signed-off-by: Paul Gortmaker <>
    net/sctp/bind_addr.c | 10 ++++------
    1 file changed, 4 insertions(+), 6 deletions(-)

    diff --git a/net/sctp/bind_addr.c b/net/sctp/bind_addr.c
    index faf71d1..6150ac5 100644
    --- a/net/sctp/bind_addr.c
    +++ b/net/sctp/bind_addr.c
    @@ -140,14 +140,12 @@ void sctp_bind_addr_init(struct sctp_bind_addr *bp, __u16 port)
    /* Dispose of the address list. */
    static void sctp_bind_addr_clean(struct sctp_bind_addr *bp)
    - struct sctp_sockaddr_entry *addr;
    - struct list_head *pos, *temp;
    + struct sctp_sockaddr_entry *addr, *temp;

    /* Empty the bind address list. */
    - list_for_each_safe(pos, temp, &bp->address_list) {
    - addr = list_entry(pos, struct sctp_sockaddr_entry, list);
    - list_del(pos);
    - kfree(addr);
    + list_for_each_entry_safe(addr, temp, &bp->address_list, list) {
    + list_del_rcu(&addr->list);
    + call_rcu(&addr->rcu, sctp_local_addr_free);

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      Last update: 2013-01-09 03:41    [W:3.231 / U:1.788 seconds]
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