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Commit 5fa534c9 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

coredump: ensure all coredumping tasks have SIGNAL_GROUP_COREDUMP 



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.

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: default avatarOleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Kyle Walker <kwalker@redhat.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Stanislav Kozina <skozina@redhat.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9317bb96

fs/coredump.c

+6 −6
Original line number Diff line number Diff line
@@ -280,11 +280,13 @@ static int format_corename(struct core_name *cn, struct coredump_params *cprm) 
	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;
@@ -311,10 +313,8 @@ 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);
@@ -365,8 +365,8 @@ 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;

kernel/signal.c

+1 −1
Original line number Diff line number Diff line
@@ -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.