From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Currently madvise_inject_error() pins the target via get_user_pages_fast.
The call to get_user_pages_fast is only to get the respective page
of a given address, but it is the job of the memory-poisoning handler
to deal with races, so drop the refcount grabbed by get_user_pages_fast.
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
---
mm/madvise.c | 25 +++++++++++--------------
1 file changed, 11 insertions(+), 14 deletions(-)
diff --git a/mm/madvise.c b/mm/madvise.c
index 6e023414f5c1..fbe6d402232c 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -883,6 +883,16 @@ static int madvise_inject_error(int behavior,
ret = get_user_pages_fast(start, 1, 0, &page);
if (ret != 1)
return ret;
+ /*
+ * The get_user_pages_fast() is just to get the pfn of the
+ * given address, and the refcount has nothing to do with
+ * what we try to test, so it should be released immediately.
+ * This is racy but it's intended because the real hardware
+ * errors could happen at any moment and memory error handlers
+ * must properly handle the race.
+ */
+ put_page(page);
+
pfn = page_to_pfn(page);
/*
@@ -892,16 +902,11 @@ static int madvise_inject_error(int behavior,
*/
order = compound_order(compound_head(page));
- if (PageHWPoison(page)) {
- put_page(page);
- continue;
- }
-
if (behavior == MADV_SOFT_OFFLINE) {
pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
pfn, start);
- ret = soft_offline_page(page, MF_COUNT_INCREASED);
+ ret = soft_offline_page(page, 0);
if (ret)
return ret;
continue;
@@ -909,14 +914,6 @@ static int madvise_inject_error(int behavior,
pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n",
pfn, start);
-
- /*
- * Drop the page reference taken by get_user_pages_fast(). In
- * the absence of MF_COUNT_INCREASED the memory_failure()
- * routine is responsible for pinning the page to prevent it
- * from being released back to the page allocator.
- */
- put_page(page);
ret = memory_failure(pfn, 0);
if (ret)
return ret;
--
2.12.3
