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    Subject[PATCH 1/2] Bsd_acct: plain current->real_parent access is not always safe
    This is minor, but dereferencing even current real_parent is not
    safe on debug kernels, since the memory, this points to, can be
    unmapped - RCU protection is required.

    Besides, the tgid field is deprecated and is to be replaced with
    task_tgid_xxx call (the 2nd patch), so RCU will be required anyway.

    Signed-off-by: Pavel Emelyanov <xemul@openvz.org>

    ---
    kernel/acct.c | 4 +++-
    1 files changed, 3 insertions(+), 1 deletions(-)

    diff --git a/kernel/acct.c b/kernel/acct.c
    index 521dfa5..7ff5339 100644
    --- a/kernel/acct.c
    +++ b/kernel/acct.c
    @@ -482,7 +482,9 @@ static void do_acct_process(struct file *file)
    #endif
    #if ACCT_VERSION==3
    ac.ac_pid = current->tgid;
    - ac.ac_ppid = current->real_parent->tgid;
    + rcu_read_lock();
    + ac.ac_ppid = rcu_dereference(current->real_parent)->tgid;
    + rcu_read_unlock();
    #endif

    spin_lock_irq(&current->sighand->siglock);
    --
    1.5.3.4


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