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Commit 810a56b9 authored by Mike Kravetz's avatar Mike Kravetz Committed by Linus Torvalds
Browse files

userfaultfd: hugetlbfs: fix __mcopy_atomic_hugetlb retry/error processing 

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.

[dan.carpenter@oracle.com: unmap the correct pointer]
  Link: http://lkml.kernel.org/r/20170113082608.GA3548@mwanda
[akpm@linux-foundation.org: kunmap() takes a page*, per Hugh]
Link: http://lkml.kernel.org/r/20161216144821.5183-20-aarcange@redhat.com


Signed-off-by: default avatarMike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: default avatarAndrea Arcangeli <aarcange@redhat.com>
Signed-off-by: default avatarDan Carpenter <dan.carpenter@oracle.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>
Cc: Hugh Dickins <hughd@google.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 60d4d2d2

include/linux/mm.h

+2 −1
Original line number Diff line number Diff line
@@ -2426,7 +2426,8 @@ 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;

mm/hugetlb.c

+1 −1
Original line number Diff line number Diff line
@@ -3973,7 +3973,7 @@ 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)) {

mm/memory.c

+10 −3
Original line number Diff line number Diff line
@@ -4155,7 +4155,8 @@ 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;
@@ -4163,10 +4164,16 @@ 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++) {

		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);

		if (allow_pagefault)

			kunmap(dst_page + i);

		else

			kunmap_atomic(page_kaddr);



		ret_val -= (PAGE_SIZE - rc);

mm/userfaultfd.c

+1 −1
Original line number Diff line number Diff line
@@ -274,7 +274,7 @@ static __always_inline ssize_t __mcopy_atomic_hugetlb(struct mm_struct *dst_mm, 


			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;