[141/151] mm: sigbus instead of abusing oom

[Greg KH]

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx>

commit d99be1a8ecf377c2c9b3372d36411ad6547bbd4c upstream.

When do_nonlinear_fault() realizes that the page table must have been
corrupted for it to have been called, it does print_bad_pte() and returns
...  VM_FAULT_OOM, which is hard to understand.

It made some sense when I did it for 2.6.15, when do_page_fault() just
killed the current process; but nowadays it lets the OOM killer decide who
to kill - so page table corruption in one process would be liable to kill
another.

Change it to return VM_FAULT_SIGBUS instead: that doesn't guarantee that
the process will be killed, but is good enough for such a rare
abnormality, accompanied as it is by the "BUG: Bad page map" message.

And recent HWPOISON work has copied that code into do_swap_page(), when it
finds an impossible swap entry: fix that to VM_FAULT_SIGBUS too.

Signed-off-by: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx>
Cc: Izik Eidus <ieidus@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Nick Piggin <npiggin@xxxxxxx>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Lee Schermerhorn <Lee.Schermerhorn@xxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Reviewed-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 mm/memory.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2514,7 +2514,7 @@ static int do_swap_page(struct mm_struct
 			ret = VM_FAULT_HWPOISON;
 		} else {
 			print_bad_pte(vma, address, orig_pte, NULL);
-			ret = VM_FAULT_OOM;
+			ret = VM_FAULT_SIGBUS;
 		}
 		goto out;
 	}
@@ -2910,7 +2910,7 @@ static int do_nonlinear_fault(struct mm_
 		 * Page table corrupted: show pte and kill process.
 		 */
 		print_bad_pte(vma, address, orig_pte, NULL);
-		return VM_FAULT_OOM;
+		return VM_FAULT_SIGBUS;
 	}
 
 	pgoff = pte_to_pgoff(orig_pte);


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