Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751235AbcDQR3v (ORCPT ); Sun, 17 Apr 2016 13:29:51 -0400 Received: from mail-pa0-f42.google.com ([209.85.220.42]:34540 "EHLO mail-pa0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750696AbcDQR3u (ORCPT ); Sun, 17 Apr 2016 13:29:50 -0400 Date: Sun, 17 Apr 2016 10:29:45 -0700 From: Alexei Starovoitov To: Sasha Levin Cc: ast@kernel.org, "netdev@vger.kernel.org" , LKML , Tejun Heo Subject: Re: bpf: use-after-free in array_map_alloc Message-ID: <20160417172943.GA83672@ast-mbp.thefacebook.com> References: <5713C0AD.3020102@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5713C0AD.3020102@oracle.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5689 Lines: 143 On Sun, Apr 17, 2016 at 12:58:21PM -0400, Sasha Levin wrote: > Hi all, > > I've hit the following while fuzzing with syzkaller inside a KVM tools guest > running the latest -next kernel: thanks for the report. Adding Tejun... if I read the report correctly it's not about bpf, but rather points to the issue inside percpu logic. First __alloc_percpu_gfp() is called, then the memory is freed with free_percpu() which triggers async pcpu_balance_work and then pcpu_extend_area_map is hitting use-after-free. I guess bpf percpu array map is stressing this logic the most. Any simpler steps to reproduce ? > [ 2590.845375] ================================================================== > > [ 2590.845445] BUG: KASAN: use-after-free in pcpu_extend_area_map+0x8a/0x130 at addr ffff88035452a3cc > > [ 2590.845457] Read of size 4 by task syz-executor/31307 > > [ 2590.845464] ============================================================================= > > [ 2590.845476] BUG kmalloc-128 (Tainted: G W ): kasan: bad access detected > > [ 2590.845479] ----------------------------------------------------------------------------- > > [ 2590.845479] > > [ 2590.845485] Disabling lock debugging due to kernel taint > > [ 2590.845496] INFO: Allocated in 0xbbbbbbbbbbbbbbbb age=18446609615465671625 cpu=0 pid=0 > > [ 2590.845504] pcpu_mem_zalloc+0x7e/0xc0 > > [ 2590.845521] ___slab_alloc+0x7af/0x870 > > [ 2590.845528] __slab_alloc.isra.22+0xf4/0x130 > > [ 2590.845535] __kmalloc+0x1fe/0x340 > > [ 2590.845543] pcpu_mem_zalloc+0x7e/0xc0 > > [ 2590.845551] pcpu_create_chunk+0x79/0x600 > > [ 2590.845558] pcpu_alloc+0x5d4/0xe10 > > [ 2590.845567] __alloc_percpu_gfp+0x27/0x30 > > [ 2590.845582] array_map_alloc+0x595/0x710 > > [ 2590.845590] SyS_bpf+0x336/0xba0 > > [ 2590.845605] do_syscall_64+0x2a6/0x4a0 > > [ 2590.845639] return_from_SYSCALL_64+0x0/0x6a > > [ 2590.845647] INFO: Freed in 0x10022ebb3 age=18446628393062689737 cpu=0 pid=0 > > [ 2590.845653] kvfree+0x45/0x50 > > [ 2590.845660] __slab_free+0x6a/0x2f0 > > [ 2590.845665] kfree+0x22c/0x270 > > [ 2590.845671] kvfree+0x45/0x50 > > [ 2590.845680] pcpu_balance_workfn+0x11a1/0x1280 > > [ 2590.845693] process_one_work+0x973/0x10b0 > > [ 2590.845700] worker_thread+0xcfd/0x1160 > > [ 2590.845708] kthread+0x2e7/0x300 > > [ 2590.845716] ret_from_fork+0x22/0x40 > > [ 2590.845724] INFO: Slab 0xffffea000d514a00 objects=35 used=33 fp=0xffff88035452b740 flags=0x2fffff80004080 > > [ 2590.845730] INFO: Object 0xffff88035452a3a0 @offset=9120 fp=0xbbbbbbbbbbbbbbbb > > [ 2590.845730] > > [ 2590.845743] Redzone ffff88035452a398: 00 00 00 00 00 00 00 00 ........ > > [ 2590.845751] Object ffff88035452a3a0: bb bb bb bb bb bb bb bb 00 00 00 00 00 00 00 00 ................ > > [ 2590.845758] Object ffff88035452a3b0: b0 7b 17 3f 03 88 ff ff 00 00 08 00 00 00 08 00 .{.?............ > > [ 2590.845765] Object ffff88035452a3c0: 00 00 e0 f9 ff e8 ff ff 01 00 00 00 10 00 00 00 ................ > > [ 2590.845775] Object ffff88035452a3d0: 18 83 2c 3f 03 88 ff ff e0 ff ff ff 0f 00 00 00 ..,?............ > > [ 2590.845783] Object ffff88035452a3e0: e0 a3 52 54 03 88 ff ff e0 a3 52 54 03 88 ff ff ..RT......RT.... > > [ 2590.845790] Object ffff88035452a3f0: 90 96 6b 9f ff ff ff ff e8 a7 13 3f 03 88 ff ff ..k........?.... > > [ 2590.845797] Object ffff88035452a400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > > [ 2590.845804] Object ffff88035452a410: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > > [ 2590.845811] Redzone ffff88035452a420: 00 00 00 00 00 00 00 00 ........ > > [ 2590.845818] Padding ffff88035452a558: b5 eb 22 00 01 00 00 00 .."..... > > [ 2590.845833] CPU: 0 PID: 31307 Comm: syz-executor Tainted: G B W 4.6.0-rc3-next-20160412-sasha-00023-g0b02d6d-dirty #2998 > > [ 2590.845851] 0000000000000000 00000000a66f8039 ffff880354f8fa60 ffffffffa0fc9d01 > > [ 2590.845861] ffffffff00000000 fffffbfff57ad2a0 0000000041b58ab3 ffffffffab65eee0 > > [ 2590.845870] ffffffffa0fc9b88 00000000a66f8039 ffff88035e9d4000 ffffffffab67cede > > [ 2590.845872] Call Trace: > > [ 2590.845903] dump_stack (lib/dump_stack.c:53) > [ 2590.845939] print_trailer (mm/slub.c:668) > [ 2590.845948] object_err (mm/slub.c:675) > [ 2590.845958] kasan_report_error (mm/kasan/report.c:180 mm/kasan/report.c:276) > [ 2590.846007] __asan_report_load4_noabort (mm/kasan/report.c:318) > [ 2590.846028] pcpu_extend_area_map (mm/percpu.c:445) > [ 2590.846038] pcpu_alloc (mm/percpu.c:940) > [ 2590.846128] __alloc_percpu_gfp (mm/percpu.c:1068) > [ 2590.846140] array_map_alloc (kernel/bpf/arraymap.c:36 kernel/bpf/arraymap.c:99) > [ 2590.846150] SyS_bpf (kernel/bpf/syscall.c:35 kernel/bpf/syscall.c:183 kernel/bpf/syscall.c:830 kernel/bpf/syscall.c:787) > [ 2590.846203] do_syscall_64 (arch/x86/entry/common.c:350) > [ 2590.846214] entry_SYSCALL64_slow_path (arch/x86/entry/entry_64.S:251) > [ 2590.846217] Memory state around the buggy address: > > [ 2590.846224] ffff88035452a280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > > [ 2590.846230] ffff88035452a300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > > [ 2590.846237] >ffff88035452a380: fc fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb > > [ 2590.846240] ^ > > [ 2590.846247] ffff88035452a400: fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc fc > > [ 2590.846253] ffff88035452a480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > > [ 2590.846256] ================================================================== >