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PI38211: LOAD BALANCER FOR IPV4 AND IPV6 GETS A SEGFAULT ATTEMPTING TO ACCESS A NULL POINTER.

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APAR status

  • Closed as program error.

Error description

  • Load Balancer for IPv4 and IPv6 gets a segfault attempting to
    access a nul pointer.  The following backtrace is seen in gdb:
    #0  0x0000000000421dbe in _lbll_obj2node (tolist=0x0,
        vobj=0x5615a0)
        at lb_linkedlist.c:687
    #1  0x0000000000420f05 in lbll_rmnode_nl (fromlist=0x0,
        obj=0x5615a0)
        at lb_linkedlist.c:425
    #2  0x000000000042dacd in _lbsel_ct_chooseserver (pkt=0x56d410,
        ct=0x7f443762f010, at=0x0) at lb_sel_connection.c:327
    #3  0x000000000042d10c in _lbsel_ct_choose (pkt=0x56d410)
        at lb_sel_connection.c:216
    #4  0x0000000000432be6 in lbtcpudp_pbuf_entry (pkt=0x56d410) at
        lb_tcpudp.c:86
    #5  0x000000000041b783 in lbip_pbuf_entry (pkt=0x56d410) at
        lb_ip.c:138
    #6  0x000000000041ce7e in lbipv4_entry (ethhdr=0x540185,
        iphdr=0x540193,
        bufflen=60, osopaque=0x540130) at lb_ipv4.c:117
    #7  0x0000000000402208 in lx_recv (psfd=4) at lx_entry.c:367
    #8  0x0000000000401e42 in lx_recv_pthread (psfd_parm=0x53da5c)
        at lx_entry.c:244
    

Local fix

Problem summary

  • ****************************************************************
    * USERS AFFECTED:  IBM WebSphere Application Server Edge Load  *
    *                  Balancer for ipv4 and ipv6 users            *
    ****************************************************************
    * PROBLEM DESCRIPTION: A crash can occur with the stack        *
    *                      shown in the error description.         *
    ****************************************************************
    * RECOMMENDATION:                                              *
    ****************************************************************
    A crash can occur when the load balancer receives a SYN on a
    connection which had previously been used and has expired. At
    this point, the connection is cleaned up and then a reference
    is made to it and a crash occurs due to referencing a null
    pointer.
    

Problem conclusion

  • Code was modified to check the validity of the pointer before
    referencing.
    
    Fix levels:
    7.0.0.40
    8.0.0.11
    8.5.5.6
    

Temporary fix

Comments

APAR Information

  • APAR number

    PI38211

  • Reported component name

    WS EDGE LB IPV4

  • Reported component ID

    5724H8812

  • Reported release

    850

  • Status

    CLOSED PER

  • PE

    NoPE

  • HIPER

    NoHIPER

  • Special Attention

    NoSpecatt

  • Submitted date

    2015-04-01

  • Closed date

    2015-04-01

  • Last modified date

    2015-04-01

  • APAR is sysrouted FROM one or more of the following:

  • APAR is sysrouted TO one or more of the following:

Fix information

  • Fixed component name

    WS EDGE LB IPV4

  • Fixed component ID

    5724H8812

Applicable component levels

  • R800 PSY

       UP

  • R850 PSY

       UP

[{"Business Unit":{"code":"BU059","label":"IBM Software w\/o TPS"},"Product":{"code":"SSEQTP","label":"WebSphere Application Server"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"8.5","Line of Business":{"code":"LOB45","label":"Automation"}}]

Document Information

Modified date:
28 April 2022