mm: PageBuddy and mapcount robustness
Change the _mapcount value indicating PageBuddy from -2 to -128 for
more robusteness against page_mapcount() undeflows.
Use reset_page_mapcount instead of __ClearPageBuddy in bad_page to
ignore the previous retval of PageBuddy().
Signed-off-by: Andrea Arcangeli <[email protected]>
Reported-by: Hugh Dickins <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index bd76256..7945247 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -286,7 +286,7 @@
/* Don't complain about poisoned pages */
if (PageHWPoison(page)) {
- __ClearPageBuddy(page);
+ reset_page_mapcount(page); /* remove PageBuddy */
return;
}
@@ -317,7 +317,7 @@
dump_stack();
out:
/* Leave bad fields for debug, except PageBuddy could make trouble */
- __ClearPageBuddy(page);
+ reset_page_mapcount(page); /* remove PageBuddy */
add_taint(TAINT_BAD_PAGE);
}
