[linux-yocto] [PATCH 3/8] mm/memory.c: don't forget to set softdirty on file mapped fault

[Yang Shi]

From: Cyrill Gorcunov <gorcunov at gmail.com>

commit 9aed8614af5a05cdaa32a0b78b0f1a424754a958 upstream

Otherwise we may not notice that pte was softdirty because
pte_mksoft_dirty helper _returns_ new pte but doesn't modify the
argument.

In case if page fault happend on dirty filemapping the newly created pte
may loose softdirty bit thus if a userspace program is tracking memory
changes with help of a memory tracker (CONFIG_MEM_SOFT_DIRTY) it might
miss modification of a memory page (which in worts case may lead to data
inconsistency).

Signed-off-by: Cyrill Gorcunov <gorcunov at openvz.org>
Acked-by: Pavel Emelyanov <xemul at parallels.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Yang Shi <yang.shi at windriver.com>
---
 mm/memory.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/memory.c b/mm/memory.c
index c578b05..b27a532 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3427,7 +3427,7 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 		if (flags & FAULT_FLAG_WRITE)
 			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
 		else if (pte_file(orig_pte) && pte_file_soft_dirty(orig_pte))
-			pte_mksoft_dirty(entry);
+			entry = pte_mksoft_dirty(entry);
 		if (anon) {
 			inc_mm_counter_fast(mm, MM_ANONPAGES);
 			page_add_new_anon_rmap(page, vma, address);
-- 
2.0.2