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authorOleg Nesterov <oleg@redhat.com>2012-07-29 20:22:31 +0200
committerIngo Molnar <mingo@kernel.org>2012-07-30 11:27:21 +0200
commit2fd611a991391a6050cbd139201a2e12fc306540 (patch)
tree8233d2ba7dd41e29c6477d4905b6fdc1e7a721e0
parent665605a2a207dbe1fa429b474f932d6ea138ba92 (diff)
downloadlinux-2fd611a991391a6050cbd139201a2e12fc306540.tar.bz2
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>
-rw-r--r--kernel/events/uprobes.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index bed2161620d7..9db9cdf8ff34 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;