From 2fd611a991391a6050cbd139201a2e12fc306540 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov <oleg@redhat.com> Date: Sun, 29 Jul 2012 20:22:31 +0200 Subject: [PATCH] uprobes: Suppress uprobe_munmap() from mmput() uprobe_munmap() does get_user_pages() and it is also called from the final mmput()->exit_mmap() path. This slows down exit/mmput() for no reason, and I think it is simply dangerous/wrong to try to fault-in a page into the dying mm. If nothing else, this happens after the last sync_mm_rss(), afaics handle_mm_fault() can change the task->rss_stat and make the subsequent check_mm() unhappy. Change uprobe_munmap() to check mm->mm_users != 0. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Srikar Dronamraju <srikar.vnet.ibm.com> Cc: Anton Arapov <anton@redhat.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/20120729182231.GA20336@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> --- kernel/events/uprobes.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index bed2161620d7b..9db9cdf8ff346 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -1082,6 +1082,9 @@ void uprobe_munmap(struct vm_area_struct *vma, unsigned long start, unsigned lon if (!atomic_read(&uprobe_events) || !valid_vma(vma, false)) return; + if (!atomic_read(&vma->vm_mm->mm_users)) /* called by mmput() ? */ + return; + if (!atomic_read(&vma->vm_mm->uprobes_state.count)) return; -- 2.30.2