From: daniel.m.jordan@oracle.com
To: linux-mm@kvack.org
Cc: aarcange@redhat.com, akpm@linux-foundation.org,
aneesh.kumar@linux.vnet.ibm.com, gerald.schaefer@de.ibm.com,
james.morse@arm.com, kirill.shutemov@linux.intel.com,
mhocko@suse.com, mike.kravetz@oracle.com,
n-horiguchi@ah.jp.nec.com, punit.agrawal@arm.com,
zhongjiang@huawei.com, linux-kernel@vger.kernel.org
Subject: [PATCH] mm/hugetlb: __get_user_pages ignores certain follow_hugetlb_page errors
Date: Tue, 18 Jul 2017 12:39:55 -0700 [thread overview]
Message-ID: <1500406795-58462-1-git-send-email-daniel.m.jordan@oracle.com> (raw)
Commit 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")
Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: James Morse <james.morse@arm.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Punit Agrawal <punit.agrawal@arm.com>
Cc: zhong jiang <zhongjiang@huawei.com>
---
mm/hugetlb.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 3eedb18..cc28993 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -4095,6 +4095,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
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;
@@ -4170,11 +4171,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
}
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;
}
@@ -4229,7 +4226,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
*/
*position = vaddr;
- return i ? i : -EFAULT;
+ return i ? i : err;
}
#ifndef __HAVE_ARCH_FLUSH_HUGETLB_TLB_RANGE
--
1.8.3.1
--
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next reply other threads:[~2017-07-18 19:40 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-18 19:39 daniel.m.jordan [this message]
2017-07-21 9:20 ` [PATCH] mm/hugetlb: __get_user_pages ignores certain follow_hugetlb_page errors Punit Agrawal
2017-07-22 0:05 ` Daniel Jordan
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