• S
    sched: fix divide by zero at {thread_group,task}_times · bea6832c
    Stanislaw Gruszka 提交于
    On architectures where cputime_t is 64 bit type, is possible to trigger
    divide by zero on do_div(temp, (__force u32) total) line, if total is a
    non zero number but has lower 32 bit's zeroed. Removing casting is not
    a good solution since some do_div() implementations do cast to u32
    internally.
    
    This problem can be triggered in practice on very long lived processes:
    
      PID: 2331   TASK: ffff880472814b00  CPU: 2   COMMAND: "oraagent.bin"
       #0 [ffff880472a51b70] machine_kexec at ffffffff8103214b
       #1 [ffff880472a51bd0] crash_kexec at ffffffff810b91c2
       #2 [ffff880472a51ca0] oops_end at ffffffff814f0b00
       #3 [ffff880472a51cd0] die at ffffffff8100f26b
       #4 [ffff880472a51d00] do_trap at ffffffff814f03f4
       #5 [ffff880472a51d60] do_divide_error at ffffffff8100cfff
       #6 [ffff880472a51e00] divide_error at ffffffff8100be7b
          [exception RIP: thread_group_times+0x56]
          RIP: ffffffff81056a16  RSP: ffff880472a51eb8  RFLAGS: 00010046
          RAX: bc3572c9fe12d194  RBX: ffff880874150800  RCX: 0000000110266fad
          RDX: 0000000000000000  RSI: ffff880472a51eb8  RDI: 001038ae7d9633dc
          RBP: ffff880472a51ef8   R8: 00000000b10a3a64   R9: ffff880874150800
          R10: 00007fcba27ab680  R11: 0000000000000202  R12: ffff880472a51f08
          R13: ffff880472a51f10  R14: 0000000000000000  R15: 0000000000000007
          ORIG_RAX: ffffffffffffffff  CS: 0010  SS: 0018
       #7 [ffff880472a51f00] do_sys_times at ffffffff8108845d
       #8 [ffff880472a51f40] sys_times at ffffffff81088524
       #9 [ffff880472a51f80] system_call_fastpath at ffffffff8100b0f2
          RIP: 0000003808caac3a  RSP: 00007fcba27ab6d8  RFLAGS: 00000202
          RAX: 0000000000000064  RBX: ffffffff8100b0f2  RCX: 0000000000000000
          RDX: 00007fcba27ab6e0  RSI: 000000000076d58e  RDI: 00007fcba27ab6e0
          RBP: 00007fcba27ab700   R8: 0000000000000020   R9: 000000000000091b
          R10: 00007fcba27ab680  R11: 0000000000000202  R12: 00007fff9ca41940
          R13: 0000000000000000  R14: 00007fcba27ac9c0  R15: 00007fff9ca41940
          ORIG_RAX: 0000000000000064  CS: 0033  SS: 002b
    
    Cc: stable@vger.kernel.org
    Signed-off-by: NStanislaw Gruszka <sgruszka@redhat.com>
    Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
    Link: http://lkml.kernel.org/r/20120808092714.GA3580@redhat.comSigned-off-by: NThomas Gleixner <tglx@linutronix.de>
    bea6832c
core.c 206.6 KB