From: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Subject: mm/hugetlb.c: __get_user_pages ignores certain follow_hugetlb_page errors
9a291a7c9428 ("mm/hugetlb: report -EHWPOISON not -EFAULT when
FOLL_HWPOISON is specified") causes __get_user_pages to ignore certain
errors from follow_hugetlb_page. After such error, __get_user_pages
subsequently calls faultin_page on the same VMA and start address that
follow_hugetlb_page failed on instead of returning the error immediately
as it should.
In follow_hugetlb_page, when hugetlb_fault returns a value covered under
VM_FAULT_ERROR, follow_hugetlb_page returns it without setting nr_pages to
0 as __get_user_pages expects in this case, which causes the following to
happen in __get_user_pages: the "while (nr_pages)" check succeeds, we skip
the "if (!vma..." check because we got a VMA the last time around, we find
no page with follow_page_mask, and we call faultin_page, which calls
hugetlb_fault for the second time.
This issue also slightly changes how __get_user_pages works. Before, it
only returned error if it had made no progress (i = 0). But now,
follow_hugetlb_page can clobber "i" with an error code since its new
return path doesn't check for progress. So if "i" is nonzero before a
failing call to follow_hugetlb_page, that indication of progress is lost
and __get_user_pages can return error even if some pages were successfully
pinned.
To fix this, change follow_hugetlb_page so that it updates nr_pages,
allowing __get_user_pages to fail immediately and restoring the "error
only if no progress" behavior to __get_user_pages.
Tested that __get_user_pages returns when expected on error from
hugetlb_fault in follow_hugetlb_page.
Fixes: 9a291a7c9428 ("mm/hugetlb: report -EHWPOISON not -EFAULT when FOLL_HWPOISON is specified")
Link: http://lkml.kernel.org/r/1500406795-58462-1-git-send-email-daniel.m.jordan@xxxxxxxxxx
Signed-off-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Acked-by: Punit Agrawal <punit.agrawal@xxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: zhong jiang <zhongjiang@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [4.12.x]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff -puN mm/hugetlb.c~mm-hugetlb-__get_user_pages-ignores-certain-follow_hugetlb_page-errors mm/hugetlb.c
--- a/mm/hugetlb.c~mm-hugetlb-__get_user_pages-ignores-certain-follow_hugetlb_page-errors
+++ a/mm/hugetlb.c
@@ -4078,6 +4078,7 @@ long follow_hugetlb_page(struct mm_struc
unsigned long vaddr = *position;
unsigned long remainder = *nr_pages;
struct hstate *h = hstate_vma(vma);
+ int err = -EFAULT;
while (vaddr < vma->vm_end && remainder) {
pte_t *pte;
@@ -4154,11 +4155,7 @@ long follow_hugetlb_page(struct mm_struc
}
ret = hugetlb_fault(mm, vma, vaddr, fault_flags);
if (ret & VM_FAULT_ERROR) {
- int err = vm_fault_to_errno(ret, flags);
-
- if (err)
- return err;
-
+ err = vm_fault_to_errno(ret, flags);
remainder = 0;
break;
}
@@ -4213,7 +4210,7 @@ same_page:
*/
*position = vaddr;
- return i ? i : -EFAULT;
+ return i ? i : err;
}
#ifndef __HAVE_ARCH_FLUSH_HUGETLB_TLB_RANGE
_