The subject is truncated. It is missing SIGNAL_GROUP_COREDUMP
On Tue 29-09-15 17:55:02, Oleg Nesterov wrote:
> task_will_free_mem() is wrong in many ways, and in particular the
> SIGNAL_GROUP_COREDUMP check is not reliable: a task can participate
> in the coredumping without SIGNAL_GROUP_COREDUMP bit set.
>
> change zap_threads() paths to always set SIGNAL_GROUP_COREDUMP even
> if other CLONE_VM processes can't react to SIGKILL. Fortunately, at
> least oom-kill case if fine; it kills all tasks sharing the same mm,
> so it should also kill the process which actually dumps the core.
Yes I do not think it will make too much difference for the oom killer
but it is much better to handle all the processes sharing the mm the
same way.
>
> The change in prepare_signal() is not strictly necessary, it just
> ensures that the patch does not bring another subtle behavioural
> change. But it reminds us that this SIGNAL_GROUP_EXIT/COREDUMP case
> needs more changes.
>
> Signed-off-by: Oleg Nesterov <o...@redhat.com>
Acked-by: Michal Hocko <mho...@suse.com>
> ---
> fs/coredump.c | 12 ++++++------
> kernel/signal.c | 2 +-
> 2 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/fs/coredump.c b/fs/coredump.c
> index 53d7d46..4fed8d0 100644
> --- a/fs/coredump.c
> +++ b/fs/coredump.c
> @@ -282,11 +282,13 @@ out:
> return ispipe;
> }
>
> -static int zap_process(struct task_struct *start, int exit_code)
> +static int zap_process(struct task_struct *start, int exit_code, int flags)
> {
> struct task_struct *t;
> int nr = 0;
>
> + /* ignore all signals except SIGKILL, see prepare_signal() */
> + start->signal->flags = SIGNAL_GROUP_COREDUMP | flags;
> start->signal->group_exit_code = exit_code;
> start->signal->group_stop_count = 0;
>
> @@ -313,10 +315,8 @@ static int zap_threads(struct task_struct *tsk, struct
> mm_struct *mm,
> spin_lock_irq(&tsk->sighand->siglock);
> if (!signal_group_exit(tsk->signal)) {
> mm->core_state = core_state;
> - nr = zap_process(tsk, exit_code);
> tsk->signal->group_exit_task = tsk;
> - /* ignore all signals except SIGKILL, see prepare_signal() */
> - tsk->signal->flags = SIGNAL_GROUP_COREDUMP;
> + nr = zap_process(tsk, exit_code, 0);
> clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
> }
> spin_unlock_irq(&tsk->sighand->siglock);
> @@ -367,8 +367,8 @@ static int zap_threads(struct task_struct *tsk, struct
> mm_struct *mm,
> if (p->mm) {
> if (unlikely(p->mm == mm)) {
> lock_task_sighand(p, &flags);
> - nr += zap_process(p, exit_code);
> - p->signal->flags = SIGNAL_GROUP_EXIT;
> + nr += zap_process(p, exit_code,
> + SIGNAL_GROUP_EXIT);
> unlock_task_sighand(p, &flags);
> }
> break;
> diff --git a/kernel/signal.c b/kernel/signal.c
> index f2cbd4e..c0b01fe 100644
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -788,7 +788,7 @@ static bool prepare_signal(int sig, struct task_struct
> *p, bool force)
> sigset_t flush;
>
> if (signal->flags & (SIGNAL_GROUP_EXIT | SIGNAL_GROUP_COREDUMP)) {
> - if (signal->flags & SIGNAL_GROUP_COREDUMP)
> + if (!(signal->flags & SIGNAL_GROUP_EXIT))
> return sig == SIGKILL;
> /*
> * The process is in the middle of dying, nothing to do.
> --
> 2.4.3
--
Michal Hocko
SUSE Labs
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
