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[178.122.97.159]) by smtp.gmail.com with ESMTPSA id d26sm1389830ljc.15.2019.03.04.00.19.20 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 04 Mar 2019 00:19:20 -0800 (PST) Received: by kshutemo-mobl1.localdomain (Postfix, from userid 1000) id 441613007CD; Mon, 4 Mar 2019 11:19:19 +0300 (+03) Date: Mon, 4 Mar 2019 11:19:19 +0300 From: "Kirill A. Shutemov" To: Jan Stancek Cc: 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, mgorman@techsingularity.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] mm/memory.c: do_fault: avoid usage of stale vm_area_struct Message-ID: <20190304081918.rrhyhyze237bpkqf@kshutemo-mobl1> References: <20190302185144.GD31083@redhat.com> <5b3fdf19e2a5be460a384b936f5b56e13733f1b8.1551595137.git.jstancek@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5b3fdf19e2a5be460a384b936f5b56e13733f1b8.1551595137.git.jstancek@redhat.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 03, 2019 at 08:28:04AM +0100, Jan Stancek wrote: > 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);| > | > > 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 > Reviewed-by: Andrea Arcangeli Acked-by: Kirill A. Shutemov -- Kirill A. Shutemov