Commit 4fe7efdb authored Jun 20, 2012 by Konstantin Khlebnikov Committed by Linus Torvalds Jun 20, 2012

mm: correctly synchronize rss-counters at exit/exec



do_exit() and exec_mmap() call sync_mm_rss() before mm_release() does
put_user(clear_child_tid) which can update task->rss_stat and thus make
mm->rss_stat inconsistent.  This triggers the "BUG:" printk in check_mm().

Let's fix this bug in the safest way, and optimize/cleanup this later.

Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent e0897d75

fs/exec.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -819,10 +819,10 @@ static int exec_mmap(struct mm_struct *mm)
		/* Notify parent that we're no longer interested in the old VM */
		tsk = current;
		old_mm = current->mm;
		sync_mm_rss(old_mm);
		mm_release(tsk, old_mm);

		if (old_mm) {
		sync_mm_rss(old_mm);
		/*
		* Make sure that if there is a core dump in progress
		* for the old mm, we get out and die instead of going

kernel/exit.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -643,6 +643,7 @@ static void exit_mm(struct task_struct * tsk)
		mm_release(tsk, mm);
		if (!mm)
		return;
		sync_mm_rss(mm);
		/*
		* Serialize with any possible pending coredump.
		* We must hold mmap_sem around checking core_state