From: Jan Stancek <jstancek@redhat.com>
To: linux-mm@kvack.org, akpm@linux-foundation.org,
willy@infradead.org, peterz@infradead.org, riel@surriel.com,
mhocko@suse.com, ying.huang@intel.com, jrdr.linux@gmail.com,
jglisse@redhat.com, aneesh.kumar@linux.ibm.com, david@redhat.com,
aarcange@redhat.com, raquini@redhat.com, rientjes@google.com,
kirill@shutemov.name, mgorman@techsingularity.net,
jstancek@redhat.com
Cc: linux-kernel@vger.kernel.org
Subject: [PATCH v3] mm/memory.c: do_fault: avoid usage of stale vm_area_struct
Date: Sun, 3 Mar 2019 08:28:04 +0100 [thread overview]
Message-ID: <5b3fdf19e2a5be460a384b936f5b56e13733f1b8.1551595137.git.jstancek@redhat.com> (raw)
In-Reply-To: <20190302185144.GD31083@redhat.com>
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
Signed-off-by: Jan Stancek <jstancek@redhat.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
---
mm/memory.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/mm/memory.c b/mm/memory.c
index e11ca9dd823f..e8d69ade5acc 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3517,10 +3517,13 @@ static vm_fault_t do_shared_fault(struct vm_fault *vmf)
* 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;
/*
@@ -3561,7 +3564,7 @@ static vm_fault_t do_fault(struct vm_fault *vmf)
/* 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;
--
1.8.3.1
next prev parent reply other threads:[~2019-03-03 7:28 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-02 15:11 [PATCH] mm/memory.c: do_fault: avoid usage of stale vm_area_struct Jan Stancek
2019-03-02 17:10 ` Matthew Wilcox
2019-03-02 18:00 ` Jan Stancek
2019-03-02 18:19 ` [PATCH v2] " Jan Stancek
2019-03-02 18:45 ` Peter Zijlstra
2019-03-02 18:51 ` Andrea Arcangeli
2019-03-03 7:27 ` Jan Stancek
2019-03-03 7:28 ` Jan Stancek [this message]
2019-03-03 10:36 ` [PATCH v3] " Matthew Wilcox
2019-03-04 0:13 ` Rafael Aquini
2019-03-04 8:10 ` Minchan Kim
2019-03-04 8:19 ` Kirill A. Shutemov
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