x86: add might_sleep() to do_page_fault()

Impact: widen debug checks

VirtualBox calls do_page_fault() from an atomic context but runs into a
might_sleep() way pas this point, cure that.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 6 insertions, 0 deletions

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 8f4b859a04b3..eb4d7fe05938 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -888,6 +888,12 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
                         return;
                 }
                 down_read(&mm->mmap_sem);
+        } else {
+                /*
+                 * The above down_read_trylock() might have succeeded in which
+                 * case we'll have missed the might_sleep() from down_read().
+                 */
+                might_sleep();
         }
 
         vma = find_vma(mm, address);