lkml.org 
[lkml]   [2017]   [Nov]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.14 003/193] s390/runtime instrumention: fix possible memory corruption
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Heiko Carstens <heiko.carstens@de.ibm.com>

    commit d6e646ad7cfa7034d280459b2b2546288f247144 upstream.

    For PREEMPT enabled kernels the runtime instrumentation (RI) code
    contains a possible use-after-free bug. If a task that makes use of RI
    exits, it will execute do_exit() while still enabled for preemption.

    That function will call exit_thread_runtime_instr() via
    exit_thread(). If exit_thread_runtime_instr() gets preempted after the
    RI control block of the task has been freed but before the pointer to
    it is set to NULL, then save_ri_cb(), called from switch_to(), will
    write to already freed memory.

    Avoid this and simply disable preemption while freeing the control
    block and setting the pointer to NULL.

    Fixes: e4b8b3f33fca ("s390: add support for runtime instrumentation")
    Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
    Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
    Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    arch/s390/kernel/runtime_instr.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    --- a/arch/s390/kernel/runtime_instr.c
    +++ b/arch/s390/kernel/runtime_instr.c
    @@ -50,11 +50,13 @@ void exit_thread_runtime_instr(void)
    {
    struct task_struct *task = current;

    + preempt_disable();
    if (!task->thread.ri_cb)
    return;
    disable_runtime_instr();
    kfree(task->thread.ri_cb);
    task->thread.ri_cb = NULL;
    + preempt_enable();
    }

    SYSCALL_DEFINE1(s390_runtime_instr, int, command)
    @@ -65,9 +67,7 @@ SYSCALL_DEFINE1(s390_runtime_instr, int,
    return -EOPNOTSUPP;

    if (command == S390_RUNTIME_INSTR_STOP) {
    - preempt_disable();
    exit_thread_runtime_instr();
    - preempt_enable();
    return 0;
    }


    \
     
     \ /
      Last update: 2017-11-28 12:43    [W:3.204 / U:0.132 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site