lkml.org 
[lkml]   [2009]   [Jan]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[PATCH 4/7][v7] Protect cinit from unblocked SIG_DFL signals
    Minor update - set 'from_ancestor_ns' parameter to 0 in send_sigque().

    ---

    From: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
    Date: Wed, 24 Dec 2008 14:03:57 -0800
    Subject: [PATCH 4/7][v7] Protect cinit from unblocked SIG_DFL signals

    Drop early any SIG_DFL or SIG_IGN signals to container-init from within
    the same container. But queue SIGSTOP and SIGKILL to the container-init
    if they are from an ancestor container.

    Blocked, fatal signals (i.e when SIG_DFL is to terminate) from within the
    container can still terminate the container-init. That will be addressed
    in the next patch.

    Note: To be bisect-safe, SIGNAL_UNKILLABLE will be set for container-inits
    in a follow-on patch. Until then, this patch is just a preparatory
    step.

    Changelog[v7]:
    - (Oleg Nesterov) Bugfix: send_sigqueue() should use from_ancestor_ns=0
    - siginfo_from_user(), siginfo_from_ancestor_ns() are needed in only
    one place. Remove them and move their logic into send_signal().
    Seems to make code more easier to read :-)

    Changelog[v6]:
    - (Roland McGrath) Remove unnecessary helper signal_task_unkillable()
    and fold checks into sig_task_ignored().

    Changelog[v4]:
    - (Oleg Nesterov) Remove SIGNAL_UNKILLABLE_FROM_NS and rename
    'same_ns' to 'from_ancestor_ns'.
    - SIGNAL_UNKILLABLE is not yet set for container-inits (will be
    set in follow-on patch).

    Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
    ---
    kernel/signal.c | 28 +++++++++++++++++++---------
    1 files changed, 19 insertions(+), 9 deletions(-)

    diff --git a/kernel/signal.c b/kernel/signal.c
    index bb3b6f5..35556aa 100644
    --- a/kernel/signal.c
    +++ b/kernel/signal.c
    @@ -53,20 +53,21 @@ static int sig_handler_ignored(void __user *handler, int sig)
    (handler == SIG_DFL && sig_kernel_ignore(sig));
    }

    -static int sig_task_ignored(struct task_struct *t, int sig)
    +static int sig_task_ignored(struct task_struct *t, int sig,
    + int from_ancestor_ns)
    {
    void __user *handler;

    handler = sig_handler(t, sig);

    if (unlikely(t->signal->flags & SIGNAL_UNKILLABLE) &&
    - handler == SIG_DFL)
    + handler == SIG_DFL && !from_ancestor_ns)
    return 1;

    return sig_handler_ignored(handler, sig);
    }

    -static int sig_ignored(struct task_struct *t, int sig)
    +static int sig_ignored(struct task_struct *t, int sig, int from_ancestor_ns)
    {
    /*
    * Blocked signals are never ignored, since the
    @@ -76,7 +77,7 @@ static int sig_ignored(struct task_struct *t, int sig)
    if (sigismember(&t->blocked, sig) || sigismember(&t->real_blocked, sig))
    return 0;

    - if (!sig_task_ignored(t, sig))
    + if (!sig_task_ignored(t, sig, from_ancestor_ns))
    return 0;

    /*
    @@ -632,7 +633,7 @@ static int check_kill_permission(int sig, struct siginfo *info,
    * Returns true if the signal should be actually delivered, otherwise
    * it should be dropped.
    */
    -static int prepare_signal(int sig, struct task_struct *p)
    +static int prepare_signal(int sig, struct task_struct *p, int from_ancestor_ns)
    {
    struct signal_struct *signal = p->signal;
    struct task_struct *t;
    @@ -716,7 +717,7 @@ static int prepare_signal(int sig, struct task_struct *p)
    }
    }

    - return !sig_ignored(p, sig);
    + return !sig_ignored(p, sig, from_ancestor_ns);
    }

    /*
    @@ -830,7 +831,8 @@ static int __send_signal(int sig, struct siginfo *info, struct task_struct *t,
    trace_sched_signal_send(sig, t);

    assert_spin_locked(&t->sighand->siglock);
    - if (!prepare_signal(sig, t))
    +
    + if (!prepare_signal(sig, t, from_ancestor_ns))
    return 0;

    pending = group ? &t->signal->shared_pending : &t->pending;
    @@ -899,7 +901,15 @@ out_set:
    static int send_signal(int sig, struct siginfo *info, struct task_struct *t,
    int group)
    {
    - return __send_signal(sig, info, t, group, 0);
    + int from_ancestor_ns = 0;
    +
    +#ifdef CONFIG_PID_NS
    + if (!is_si_special(info) && SI_FROMUSER(info) &&
    + task_pid_nr_ns(current, task_active_pid_ns(t)) <= 0)
    + from_ancestor_ns = 1;
    +#endif
    +
    + return __send_signal(sig, info, t, group, from_ancestor_ns);
    }

    int print_fatal_signals;
    @@ -1331,7 +1341,7 @@ int send_sigqueue(struct sigqueue *q, struct task_struct *t, int group)
    goto ret;

    ret = 1; /* the signal is ignored */
    - if (!prepare_signal(sig, t))
    + if (!prepare_signal(sig, t, 0))
    goto out;

    ret = 0;
    --
    1.5.2.5


    \
     
     \ /
      Last update: 2009-01-20 02:15    [W:0.026 / U:160.076 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site