From: Mike Kravetz <mike.kravetz@oracle.com>
Date: Thu, 12 Jan 2017 01:19:15 +0000 (+1100)
Subject: userfaultfd: hugetlbfs: fix __mcopy_atomic_hugetlb retry/error processing
X-Git-Tag: v4.1.12-92~16^2~8
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=bd0a437c4e3fee8e751a6056fd1de383925de6b3;p=users%2Fjedix%2Flinux-maple.git

userfaultfd: hugetlbfs: fix __mcopy_atomic_hugetlb retry/error processing

Orabug: 21685254

The new routine copy_huge_page_from_user() uses kmap_atomic() to map
PAGE_SIZE pages.  However, this prevents page faults in the subsequent
call to copy_from_user().  This is OK in the case where the routine is
copied with mmap_sema held.  However, in another case we want to allow
page faults.  So, add a new argument allow_pagefault to indicate if the
routine should allow page faults.

Link: http://lkml.kernel.org/r/20161216144821.5183-20-aarcange@redhat.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michael Rapoport <RAPOPORT@il.ibm.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from linux-next next-20170117
 commit 939d5ff6c4e48f72b3261baf8d4b82f54caf4561)
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Dhaval Giani <dhaval.giani@oracle.com>

Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>
---

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 288395e54996c..9cb12ef4c42ec 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2164,7 +2164,8 @@ extern void copy_user_huge_page(struct page *dst, struct page *src,
 				unsigned int pages_per_huge_page);
 extern long copy_huge_page_from_user(struct page *dst_page,
 				const void __user *usr_src,
-				unsigned int pages_per_huge_page);
+				unsigned int pages_per_huge_page,
+				bool allow_pagefault);
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */
 
 extern struct page_ext_operations debug_guardpage_ops;
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 85b55f2df8fc0..5098c726714b0 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3840,7 +3840,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
 
 		ret = copy_huge_page_from_user(page,
 						(const void __user *) src_addr,
-						pages_per_huge_page(h));
+						pages_per_huge_page(h), false);
 
 		/* fallback to copy_from_user outside mmap_sem */
 		if (unlikely(ret)) {
diff --git a/mm/memory.c b/mm/memory.c
index 739a6a8126932..df27b564c41f6 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3852,7 +3852,8 @@ void copy_user_huge_page(struct page *dst, struct page *src,
 
 long copy_huge_page_from_user(struct page *dst_page,
 				const void __user *usr_src,
-				unsigned int pages_per_huge_page)
+				unsigned int pages_per_huge_page,
+				bool allow_pagefault)
 {
 	void *src = (void *)usr_src;
 	void *page_kaddr;
@@ -3860,11 +3861,17 @@ long copy_huge_page_from_user(struct page *dst_page,
 	unsigned long ret_val = pages_per_huge_page * PAGE_SIZE;
 
 	for (i = 0; i < pages_per_huge_page; i++) {
-		page_kaddr = kmap_atomic(dst_page + i);
+		if (allow_pagefault)
+			page_kaddr = kmap(dst_page + i);
+		else
+			page_kaddr = kmap_atomic(dst_page + i);
 		rc = copy_from_user(page_kaddr,
 				(const void __user *)(src + i * PAGE_SIZE),
 				PAGE_SIZE);
-		kunmap_atomic(page_kaddr);
+		if (allow_pagefault)
+			kunmap(page_kaddr);
+		else
+			kunmap_atomic(page_kaddr);
 
 		ret_val -= (PAGE_SIZE - rc);
 		if (rc)
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 1b36e191e833e..8b1c09b5f8cb8 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -274,7 +274,7 @@ retry:
 
 			err = copy_huge_page_from_user(page,
 						(const void __user *)src_addr,
-						pages_per_huge_page(h));
+						pages_per_huge_page(h), true);
 			if (unlikely(err)) {
 				err = -EFAULT;
 				goto out;