path: root/mm
diff options
authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2016-09-19 14:44:01 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-09-19 15:36:16 -0700
commitc131f751ab1a852d4dd4b490b3a7fbba7d738de5 (patch)
tree8aad30641286414906d71e5bcfa7f8274998a601 /mm
parentd8e3875431956c1f78e142d531f490f76c760ce3 (diff)
khugepaged: fix use-after-free in collapse_huge_page()
hugepage_vma_revalidate() tries to re-check if we still should try to collapse small pages into huge one after the re-acquiring mmap_sem. The problem Dmitry Vyukov reported[1] is that the vma found by hugepage_vma_revalidate() can be suitable for huge pages, but not the same vma we had before dropping mmap_sem. And dereferencing original vma can lead to fun results.. Let's use vma hugepage_vma_revalidate() found instead of assuming it's the same as what we had before the lock was dropped. [1] http://lkml.kernel.org/r/CACT4Y+Z3gigBvhca9kRJFcjX0G70V_nRhbwKBU+yGoESBDKi9Q@mail.gmail.com Link: http://lkml.kernel.org/r/20160907122559.GA6542@black.fi.intel.com Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reported-by: Dmitry Vyukov <dvyukov@google.com> Reviewed-by: Andrea Arcangeli <aarcange@redhat.com> Cc: Ebru Akagunduz <ebru.akagunduz@gmail.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Vegard Nossum <vegard.nossum@oracle.com> Cc: Sasha Levin <levinsasha928@gmail.com> Cc: Konstantin Khlebnikov <koct9i@gmail.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Greg Thelen <gthelen@google.com> Cc: Suleiman Souhlal <suleiman@google.com> Cc: Hugh Dickins <hughd@google.com> Cc: David Rientjes <rientjes@google.com> Cc: syzkaller <syzkaller@googlegroups.com> Cc: Kostya Serebryany <kcc@google.com> Cc: Alexander Potapenko <glider@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
1 files changed, 8 insertions, 7 deletions
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 79c52d0061af..62339bf3c726 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -838,7 +838,8 @@ static bool hugepage_vma_check(struct vm_area_struct *vma)
* value (scan code).
-static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address)
+static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
+ struct vm_area_struct **vmap)
struct vm_area_struct *vma;
unsigned long hstart, hend;
@@ -846,7 +847,7 @@ static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address)
if (unlikely(khugepaged_test_exit(mm)))
- vma = find_vma(mm, address);
+ *vmap = vma = find_vma(mm, address);
if (!vma)
@@ -898,7 +899,7 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm,
/* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
if (ret & VM_FAULT_RETRY) {
- if (hugepage_vma_revalidate(mm, address)) {
+ if (hugepage_vma_revalidate(mm, address, &fe.vma)) {
/* vma is no longer available, don't continue to swapin */
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
return false;
@@ -923,7 +924,6 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm,
static void collapse_huge_page(struct mm_struct *mm,
unsigned long address,
struct page **hpage,
- struct vm_area_struct *vma,
int node, int referenced)
pmd_t *pmd, _pmd;
@@ -933,6 +933,7 @@ static void collapse_huge_page(struct mm_struct *mm,
spinlock_t *pmd_ptl, *pte_ptl;
int isolated = 0, result = 0;
struct mem_cgroup *memcg;
+ struct vm_area_struct *vma;
unsigned long mmun_start; /* For mmu_notifiers */
unsigned long mmun_end; /* For mmu_notifiers */
gfp_t gfp;
@@ -961,7 +962,7 @@ static void collapse_huge_page(struct mm_struct *mm,
- result = hugepage_vma_revalidate(mm, address);
+ result = hugepage_vma_revalidate(mm, address, &vma);
if (result) {
mem_cgroup_cancel_charge(new_page, memcg, true);
@@ -994,7 +995,7 @@ static void collapse_huge_page(struct mm_struct *mm,
* handled by the anon_vma lock + PG_lock.
- result = hugepage_vma_revalidate(mm, address);
+ result = hugepage_vma_revalidate(mm, address, &vma);
if (result)
goto out;
/* check if the pmd is still valid */
@@ -1202,7 +1203,7 @@ out_unmap:
if (ret) {
node = khugepaged_find_target_node();
/* collapse_huge_page will return with the mmap_sem released */
- collapse_huge_page(mm, address, hpage, vma, node, referenced);
+ collapse_huge_page(mm, address, hpage, node, referenced);
trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,