From: Miaohe Lin <linmiaohe@xxxxxxxxxx>
There is a race condition between memory_failure_hugetlb() and hugetlb
free/demotion, which causes setting PageHWPoison flag on the wrong page.
The one simple result is that wrong processes can be killed, but another
(more serious) one is that the actual error is left unhandled, so no one
prevents later access to it, and that might lead to more serious results
like consuming corrupted data.
Think about the below race window:
CPU 1 CPU 2
memory_failure_hugetlb
struct page *head = compound_head(p);
hugetlb page might be freed to
buddy, or even changed to another
compound page.
get_hwpoison_page -- page is not what we want now...
The compound_head is called outside hugetlb_lock, so the head is not
reliable.
So set PageHWPoison flag after passing prechecks. And to detect
potential violation, this patch also introduces a new action type
MF_MSG_DIFFERENT_PAGE_SIZE.
Reported-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
ChangeLog v3 -> v4:
- squash with "mm/memory-failure.c: fix race with changing page
compound again".
- update patch subject and description based on it.
ChangeLog v2 -> v3:
- rename the patch because page lock is not the primary factor to
solve the reported issue.
- updated description in the same manner.
- call page_handle_poison() instead of __page_handle_poison() for
free hugepage case.
- reorder put_page and unlock_page (thanks to Miaohe Lin)
ChangeLog v1 -> v2:
- pass subpage to get_hwpoison_huge_page() instead of head page.
- call compound_head() in hugetlb_lock to avoid race with hugetlb
demotion/free.
---
include/linux/mm.h | 1 +
include/ras/ras_event.h | 1 +
mm/hugetlb.c | 8 +++---
mm/memory-failure.c | 55 ++++++++++++++++++++++++-----------------
4 files changed, 40 insertions(+), 25 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 5744a3fc4716..68c101b399b7 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3244,6 +3244,7 @@ enum mf_action_page_type {
MF_MSG_BUDDY,
MF_MSG_DAX,
MF_MSG_UNSPLIT_THP,
+ MF_MSG_DIFFERENT_PAGE_SIZE,
MF_MSG_UNKNOWN,
};
diff --git a/include/ras/ras_event.h b/include/ras/ras_event.h
index d0337a41141c..1e694fd239b9 100644
--- a/include/ras/ras_event.h
+++ b/include/ras/ras_event.h
@@ -374,6 +374,7 @@ TRACE_EVENT(aer_event,
EM ( MF_MSG_BUDDY, "free buddy page" ) \
EM ( MF_MSG_DAX, "dax page" ) \
EM ( MF_MSG_UNSPLIT_THP, "unsplit thp" ) \
+ EM ( MF_MSG_DIFFERENT_PAGE_SIZE, "different page size" ) \
EMe ( MF_MSG_UNKNOWN, "unknown page" )
/*
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index f294db835f4b..345fed90842e 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6761,14 +6761,16 @@ bool isolate_huge_page(struct page *page, struct list_head *list)
int get_hwpoison_huge_page(struct page *page, bool *hugetlb)
{
+ struct page *head;
int ret = 0;
*hugetlb = false;
spin_lock_irq(&hugetlb_lock);
- if (PageHeadHuge(page)) {
+ head = compound_head(page);
+ if (PageHeadHuge(head)) {
*hugetlb = true;
- if (HPageFreed(page) || HPageMigratable(page))
- ret = get_page_unless_zero(page);
+ if (HPageFreed(head) || HPageMigratable(head))
+ ret = get_page_unless_zero(head);
else
ret = -EBUSY;
}
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 59d0de9beb60..5842aaadcc99 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -732,6 +732,7 @@ static const char * const action_page_types[] = {
[MF_MSG_BUDDY] = "free buddy page",
[MF_MSG_DAX] = "dax page",
[MF_MSG_UNSPLIT_THP] = "unsplit thp",
+ [MF_MSG_DIFFERENT_PAGE_SIZE] = "different page size",
[MF_MSG_UNKNOWN] = "unknown page",
};
@@ -1192,7 +1193,7 @@ static int __get_hwpoison_page(struct page *page, unsigned long flags)
int ret = 0;
bool hugetlb = false;
- ret = get_hwpoison_huge_page(head, &hugetlb);
+ ret = get_hwpoison_huge_page(page, &hugetlb);
if (hugetlb)
return ret;
@@ -1279,11 +1280,10 @@ static int get_any_page(struct page *p, unsigned long flags)
static int __get_unpoison_page(struct page *page)
{
- struct page *head = compound_head(page);
int ret = 0;
bool hugetlb = false;
- ret = get_hwpoison_huge_page(head, &hugetlb);
+ ret = get_hwpoison_huge_page(page, &hugetlb);
if (hugetlb)
return ret;
@@ -1501,34 +1501,21 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
struct page *head = compound_head(p);
int res;
unsigned long page_flags;
-
- if (TestSetPageHWPoison(head)) {
- pr_err("Memory failure: %#lx: already hardware poisoned\n",
- pfn);
- res = -EHWPOISON;
- if (flags & MF_ACTION_REQUIRED)
- res = kill_accessing_process(current, page_to_pfn(head), flags);
- return res;
- }
-
- num_poisoned_pages_inc();
+ bool put = false;
+ bool already_hwpoisoned = false;
if (!(flags & MF_COUNT_INCREASED)) {
res = get_hwpoison_page(p, flags);
if (!res) {
lock_page(head);
if (hwpoison_filter(p)) {
- if (TestClearPageHWPoison(head))
- num_poisoned_pages_dec();
unlock_page(head);
return -EOPNOTSUPP;
}
unlock_page(head);
res = MF_FAILED;
- if (__page_handle_poison(p)) {
- page_ref_inc(p);
+ if (page_handle_poison(p, true, false))
res = MF_RECOVERED;
- }
action_result(pfn, MF_MSG_FREE_HUGE, res);
return res == MF_RECOVERED ? 0 : -EBUSY;
} else if (res < 0) {
@@ -1538,16 +1525,32 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
}
lock_page(head);
+
+ /*
+ * The page could have changed compound pages due to race window.
+ * If this happens just bail out.
+ */
+ if (!PageHuge(p) || compound_head(p) != head) {
+ action_result(pfn, MF_MSG_DIFFERENT_PAGE_SIZE, MF_IGNORED);
+ res = -EBUSY;
+ goto out;
+ }
+
page_flags = head->flags;
if (hwpoison_filter(p)) {
- if (TestClearPageHWPoison(head))
- num_poisoned_pages_dec();
- put_page(p);
+ put = true;
res = -EOPNOTSUPP;
goto out;
}
+ if (TestSetPageHWPoison(head)) {
+ put = already_hwpoisoned = true;
+ goto out;
+ }
+
+ num_poisoned_pages_inc();
+
/*
* TODO: hwpoison for pud-sized hugetlb doesn't work right now, so
* simply disable it. In order to make it work properly, we need
@@ -1572,6 +1575,14 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
return identify_page_state(pfn, p, page_flags);
out:
unlock_page(head);
+ if (put)
+ put_page(p);
+ if (already_hwpoisoned) {
+ pr_err("Memory failure: %#lx: already hardware poisoned\n", pfn);
+ res = -EHWPOISON;
+ if (flags & MF_ACTION_REQUIRED)
+ res = kill_accessing_process(current, page_to_pfn(head), flags);
+ }
return res;
}
--
2.25.1
