Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755621AbaLVSB1 (ORCPT ); Mon, 22 Dec 2014 13:01:27 -0500 Received: from mta-out1.inet.fi ([62.71.2.227]:53605 "EHLO kirsi1.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755342AbaLVSBZ (ORCPT ); Mon, 22 Dec 2014 13:01:25 -0500 Date: Mon, 22 Dec 2014 20:01:02 +0200 From: "Kirill A. Shutemov" To: Sasha Levin , Davidlohr Bueso Cc: "linux-mm@kvack.org" , LKML , Andrew Morton , Dave Jones Subject: Re: mm: NULL ptr deref in unlink_file_vma Message-ID: <20141222180102.GA8072@node.dhcp.inet.fi> References: <549832E2.8060609@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <549832E2.8060609@oracle.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Dec 22, 2014 at 10:04:02AM -0500, Sasha Levin wrote: > Hi all, > > While fuzzing with trinity inside a KVM tools guest running the latest -next > kernel, I've stumbled on the following spew: > > [ 432.376425] BUG: unable to handle kernel NULL pointer dereference at 0000000000000038 > [ 432.378876] IP: down_write (./arch/x86/include/asm/rwsem.h:105 ./arch/x86/include/asm/rwsem.h:121 kernel/locking/rwsem.c:71) Looks like vma->vm_file->mapping is NULL. Somebody freed ->vm_file from under us? I suspect Davidlohr's patchset on i_mmap_lock, but I cannot find any code path which could lead to the crash. I've noticed one strange code path, which probably is not related to the issue: unmap_mapping_range() i_mmap_lock_read(mapping); unmap_mapping_range_tree() unmap_mapping_range_vma() zap_page_range_single() unmap_single_vma() if (unlikely(is_vm_hugetlb_page(vma))) { i_mmap_lock_write(vma->vm_file->f_mapping); Is it legal to down_write() semaphore while we have it taken on read? It must be the same mapping, right? > [ 432.380085] PGD 57e5e0067 PUD 57e5e1067 PMD 0 > [ 432.380085] Oops: 0002 [#1] PREEMPT SMP KASAN > [ 432.380085] Dumping ftrace buffer: > [ 432.380085] (ftrace buffer empty) > [ 432.380085] Modules linked in: > [ 432.380085] CPU: 4 PID: 9249 Comm: trinity-subchil Not tainted 3.18.0-next-20141219-sasha-00047-gaab33f6-dirty #1627 > [ 432.380085] task: ffff8806a88c8000 ti: ffff880664f3c000 task.ti: ffff880664f3c000 > [ 432.380085] RIP: down_write (./arch/x86/include/asm/rwsem.h:105 ./arch/x86/include/asm/rwsem.h:121 kernel/locking/rwsem.c:71) > [ 432.380085] RSP: 0018:ffff880664f3fc98 EFLAGS: 00010292 > [ 432.380085] RAX: 0000000000000038 RBX: ffff880101aa7c00 RCX: 1ffff10020354f8f > [ 432.380085] RDX: ffffffff00000001 RSI: 1ffff100fe326200 RDI: 0000000000000038 > [ 432.380085] RBP: ffff880664f3fcb8 R08: 0000000000000000 R09: ffff880101aa6258 > [ 432.380085] R10: 0000000000000000 R11: 0000000000000000 R12: ffff880000025900 > [ 432.380085] R13: 0000000000000038 R14: 0000000000000000 R15: ffff880101aa7c00 > [ 432.380085] FS: 00007f21149c4700(0000) GS:ffff880216400000(0000) knlGS:0000000000000000 > [ 432.380085] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > [ 432.380085] CR2: 0000000000000038 CR3: 000000057a4f3000 CR4: 00000000000006a0 > [ 432.380085] Stack: > [ 432.380085] ffff880101aa7c00 ffff880101aa7c78 ffff880101aa6200 ffff880101aa7c00 > [ 432.380085] ffff880664f3fce8 ffffffffa1953e9d[ 432.400920] CONFIG_KASAN_INLINE enabled > [ 432.400923] GPF could be caused by NULL-ptr deref or user memory access > > [ 432.402566] ffff880101aa7c00 00007f210f9f3000 > [ 432.402566] dfffe90000000000 ffff880101aa4600 ffff880664f3fd48 ffffffffa1937821 > [ 432.402566] Call Trace: > [ 432.402566] unlink_file_vma (mm/mmap.c:264) > [ 432.402566] free_pgtables (mm/memory.c:548) > [ 432.402566] exit_mmap (mm/mmap.c:2846) > [ 432.402566] ? kmem_cache_free (mm/slub.c:2712 mm/slub.c:2721) > [ 432.402566] mmput (kernel/fork.c:659) > [ 432.402566] do_exit (./arch/x86/include/asm/thread_info.h:164 kernel/exit.c:438 kernel/exit.c:732) > [ 432.402566] ? preempt_count_sub (kernel/sched/core.c:2620) > [ 432.402566] ? __this_cpu_preempt_check (lib/smp_processor_id.c:63) > [ 432.402566] do_group_exit (include/linux/sched.h:775 kernel/exit.c:858) > [ 432.402566] SyS_exit_group (kernel/exit.c:886) > [ 432.402566] system_call_fastpath (arch/x86/kernel/entry_64.S:423) > [ 432.402566] Code: 79 05 e8 f9 e9 a6 f2 5d c3 0f 1f 80 00 00 00 00 66 66 66 66 90 48 ba 01 00 00 00 ff ff ff ff 55 48 89 f8 48 89 e5 53 48 83 ec 18 48 0f c1 10 85 d2 74 05 e8 f7 e9 a6 f2 65 48 8b 1c 25 80 b9 > All code > ======== > 0: 79 05 jns 0x7 > 2: e8 f9 e9 a6 f2 callq 0xfffffffff2a6ea00 > 7: 5d pop %rbp > 8: c3 retq > 9: 0f 1f 80 00 00 00 00 nopl 0x0(%rax) > 10: 66 66 66 66 90 data32 data32 data32 xchg %ax,%ax > 15: 48 ba 01 00 00 00 ff movabs $0xffffffff00000001,%rdx > 1c: ff ff ff > 1f: 55 push %rbp > 20: 48 89 f8 mov %rdi,%rax > 23: 48 89 e5 mov %rsp,%rbp > 26: 53 push %rbx > 27: 48 83 ec 18 sub $0x18,%rsp > 2b:* f0 48 0f c1 10 lock xadd %rdx,(%rax) <-- trapping instruction > 30: 85 d2 test %edx,%edx > 32: 74 05 je 0x39 > 34: e8 f7 e9 a6 f2 callq 0xfffffffff2a6ea30 > 39: 65 gs > 3a: 48 rex.W > 3b: 8b .byte 0x8b > 3c: 1c 25 sbb $0x25,%al > 3e: 80 .byte 0x80 > 3f: b9 .byte 0xb9 > ... > > Code starting with the faulting instruction > =========================================== > 0: f0 48 0f c1 10 lock xadd %rdx,(%rax) > 5: 85 d2 test %edx,%edx > 7: 74 05 je 0xe > 9: e8 f7 e9 a6 f2 callq 0xfffffffff2a6ea05 > e: 65 gs > f: 48 rex.W > 10: 8b .byte 0x8b > 11: 1c 25 sbb $0x25,%al > 13: 80 .byte 0x80 > 14: b9 .byte 0xb9 > ... > [ 432.402566] RIP down_write (./arch/x86/include/asm/rwsem.h:105 ./arch/x86/include/asm/rwsem.h:121 kernel/locking/rwsem.c:71) > [ 432.402566] RSP > [ 432.402566] CR2: 0000000000000038 > > > Thanks, > Sasha > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/