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Message-Id: <20190322111330.947117233@linuxfoundation.org>
Date: Fri, 22 Mar 2019 12:15:55 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Jan Stancek <jstancek@...hat.com>,
Andrea Arcangeli <aarcange@...hat.com>,
Matthew Wilcox <willy@...radead.org>,
Rafael Aquini <aquini@...hat.com>,
Minchan Kim <minchan@...nel.org>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Rik van Riel <riel@...riel.com>,
Michal Hocko <mhocko@...e.com>,
Huang Ying <ying.huang@...el.com>,
Souptick Joarder <jrdr.linux@...il.com>,
Jerome Glisse <jglisse@...hat.com>,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
David Hildenbrand <david@...hat.com>,
David Rientjes <rientjes@...gle.com>,
Mel Gorman <mgorman@...hsingularity.net>,
Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 4.19 202/280] mm/memory.c: do_fault: avoid usage of stale vm_area_struct
4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jan Stancek <jstancek@...hat.com>
commit fc8efd2ddfed3f343c11b693e87140ff358d7ff5 upstream.
LTP testcase mtest06 [1] can trigger a crash on s390x running 5.0.0-rc8.
This is a stress test, where one thread mmaps/writes/munmaps memory area
and other thread is trying to read from it:
CPU: 0 PID: 2611 Comm: mmap1 Not tainted 5.0.0-rc8+ #51
Hardware name: IBM 2964 N63 400 (z/VM 6.4.0)
Krnl PSW : 0404e00180000000 00000000001ac8d8 (__lock_acquire+0x7/0x7a8)
Call Trace:
([<0000000000000000>] (null))
[<00000000001adae4>] lock_acquire+0xec/0x258
[<000000000080d1ac>] _raw_spin_lock_bh+0x5c/0x98
[<000000000012a780>] page_table_free+0x48/0x1a8
[<00000000002f6e54>] do_fault+0xdc/0x670
[<00000000002fadae>] __handle_mm_fault+0x416/0x5f0
[<00000000002fb138>] handle_mm_fault+0x1b0/0x320
[<00000000001248cc>] do_dat_exception+0x19c/0x2c8
[<000000000080e5ee>] pgm_check_handler+0x19e/0x200
page_table_free() is called with NULL mm parameter, but because "0" is a
valid address on s390 (see S390_lowcore), it keeps going until it
eventually crashes in lockdep's lock_acquire. This crash is
reproducible at least since 4.14.
Problem is that "vmf->vma" used in do_fault() can become stale. Because
mmap_sem may be released, other threads can come in, call munmap() and
cause "vma" be returned to kmem cache, and get zeroed/re-initialized and
re-used:
handle_mm_fault |
__handle_mm_fault |
do_fault |
vma = vmf->vma |
do_read_fault |
__do_fault |
vma->vm_ops->fault(vmf); |
mmap_sem is released |
|
| do_munmap()
| remove_vma_list()
| remove_vma()
| vm_area_free()
| # vma is released
| ...
| # same vma is allocated
| # from kmem cache
| do_mmap()
| vm_area_alloc()
| memset(vma, 0, ...)
|
pte_free(vma->vm_mm, ...); |
page_table_free |
spin_lock_bh(&mm->context.lock);|
<crash> |
Cache mm_struct to avoid using potentially stale "vma".
[1] https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/mem/mtest06/mmap1.c
Link: http://lkml.kernel.org/r/5b3fdf19e2a5be460a384b936f5b56e13733f1b8.1551595137.git.jstancek@redhat.com
Signed-off-by: Jan Stancek <jstancek@...hat.com>
Reviewed-by: Andrea Arcangeli <aarcange@...hat.com>
Reviewed-by: Matthew Wilcox <willy@...radead.org>
Acked-by: Rafael Aquini <aquini@...hat.com>
Reviewed-by: Minchan Kim <minchan@...nel.org>
Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Rik van Riel <riel@...riel.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Huang Ying <ying.huang@...el.com>
Cc: Souptick Joarder <jrdr.linux@...il.com>
Cc: Jerome Glisse <jglisse@...hat.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com>
Cc: David Hildenbrand <david@...hat.com>
Cc: Andrea Arcangeli <aarcange@...hat.com>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Mel Gorman <mgorman@...hsingularity.net>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
mm/memory.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3762,10 +3762,13 @@ static vm_fault_t do_shared_fault(struct
* but allow concurrent faults).
* The mmap_sem may have been released depending on flags and our
* return value. See filemap_fault() and __lock_page_or_retry().
+ * If mmap_sem is released, vma may become invalid (for example
+ * by other thread calling munmap()).
*/
static vm_fault_t do_fault(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
+ struct mm_struct *vm_mm = vma->vm_mm;
vm_fault_t ret;
/*
@@ -3806,7 +3809,7 @@ static vm_fault_t do_fault(struct vm_fau
/* preallocated pagetable is unused: free it */
if (vmf->prealloc_pte) {
- pte_free(vma->vm_mm, vmf->prealloc_pte);
+ pte_free(vm_mm, vmf->prealloc_pte);
vmf->prealloc_pte = NULL;
}
return ret;
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