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[77.136.87.177]) by smtp.gmail.com with ESMTPSA id n17-v6sm2822123wmc.13.2018.09.06.00.00.27 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 06 Sep 2018 00:00:28 -0700 (PDT) Subject: Re: KASAN: slab-out-of-bounds Read in _decode_session6 To: syzbot , ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, dvyukov@google.com, herbert@gondor.apana.org.au, kuznet@ms2.inr.ac.ru, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, steffen.klassert@secunet.com, syzkaller-bugs@googlegroups.com, yoshfuji@linux-ipv6.org References: <0000000000002bef6405752b530b@google.com> From: Eric Dumazet Message-ID: Date: Thu, 6 Sep 2018 00:00:26 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <0000000000002bef6405752b530b@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/05/2018 08:17 PM, syzbot wrote: > syzbot has found a reproducer for the following crash on: > > HEAD commit:    b36fdc6853a3 Merge tag 'gpio-v4.19-2' of git://git.kernel... > git tree:       upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=164938d1400000 > kernel config:  https://syzkaller.appspot.com/x/.config?x=4c7e83258d6e0156 > dashboard link: https://syzkaller.appspot.com/bug?extid=acffccec848dc13fe459 > compiler:       gcc (GCC) 8.0.1 20180413 (experimental) > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=115f172e400000 > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16399be1400000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+acffccec848dc13fe459@syzkaller.appspotmail.com > > IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready > IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready > IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready > 8021q: adding VLAN 0 to HW filter on device team0 > ================================================================== > BUG: KASAN: slab-out-of-bounds in _decode_session6+0x1331/0x14e0 net/ipv6/xfrm6_policy.c:161 > Read of size 1 at addr ffff8801d4a67f07 by task syz-executor092/4673 > > CPU: 1 PID: 4673 Comm: syz-executor092 Not tainted 4.19.0-rc2+ #223 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > Call Trace: >  __dump_stack lib/dump_stack.c:77 [inline] >  dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113 >  print_address_description+0x6c/0x20b mm/kasan/report.c:256 >  kasan_report_error mm/kasan/report.c:354 [inline] >  kasan_report.cold.7+0x242/0x30d mm/kasan/report.c:412 >  __asan_report_load1_noabort+0x14/0x20 mm/kasan/report.c:430 >  _decode_session6+0x1331/0x14e0 net/ipv6/xfrm6_policy.c:161 >  __xfrm_decode_session+0x71/0x140 net/xfrm/xfrm_policy.c:2299 >  xfrm_decode_session include/net/xfrm.h:1232 [inline] >  vti6_tnl_xmit+0x3fc/0x1bb1 net/ipv6/ip6_vti.c:542 >  __netdev_start_xmit include/linux/netdevice.h:4287 [inline] >  netdev_start_xmit include/linux/netdevice.h:4296 [inline] >  xmit_one net/core/dev.c:3216 [inline] >  dev_hard_start_xmit+0x272/0xc10 net/core/dev.c:3232 >  __dev_queue_xmit+0x2ab2/0x3870 net/core/dev.c:3802 >  dev_queue_xmit+0x17/0x20 net/core/dev.c:3835 >  __bpf_tx_skb net/core/filter.c:2012 [inline] >  __bpf_redirect_common net/core/filter.c:2050 [inline] >  __bpf_redirect+0x5b7/0xae0 net/core/filter.c:2057 >  ____bpf_clone_redirect net/core/filter.c:2090 [inline] >  bpf_clone_redirect+0x2f6/0x490 net/core/filter.c:2062 >  bpf_prog_c39d1ba309a769f7+0xe9e/0x1000 > > Allocated by task 4673: >  save_stack+0x43/0xd0 mm/kasan/kasan.c:448 >  set_track mm/kasan/kasan.c:460 [inline] >  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553 >  __do_kmalloc_node mm/slab.c:3682 [inline] >  __kmalloc_node_track_caller+0x47/0x70 mm/slab.c:3696 >  __kmalloc_reserve.isra.41+0x3a/0xe0 net/core/skbuff.c:137 >  pskb_expand_head+0x230/0x10e0 net/core/skbuff.c:1463 >  skb_ensure_writable+0x3dd/0x640 net/core/skbuff.c:5129 >  __bpf_try_make_writable net/core/filter.c:1633 [inline] >  bpf_try_make_writable net/core/filter.c:1639 [inline] >  bpf_try_make_head_writable net/core/filter.c:1647 [inline] >  ____bpf_clone_redirect net/core/filter.c:2084 [inline] >  bpf_clone_redirect+0x14a/0x490 net/core/filter.c:2062 >  bpf_prog_c39d1ba309a769f7+0xe9e/0x1000 > > Freed by task 3286: >  save_stack+0x43/0xd0 mm/kasan/kasan.c:448 >  set_track mm/kasan/kasan.c:460 [inline] >  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521 >  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 >  __cache_free mm/slab.c:3498 [inline] >  kfree+0xd9/0x210 mm/slab.c:3813 >  load_elf_binary+0x2569/0x5610 fs/binfmt_elf.c:1118 >  search_binary_handler+0x17d/0x570 fs/exec.c:1653 >  exec_binprm fs/exec.c:1695 [inline] >  __do_execve_file.isra.35+0x15ff/0x2460 fs/exec.c:1819 >  do_execveat_common fs/exec.c:1866 [inline] >  do_execve fs/exec.c:1883 [inline] >  __do_sys_execve fs/exec.c:1964 [inline] >  __se_sys_execve fs/exec.c:1959 [inline] >  __x64_sys_execve+0x8f/0xc0 fs/exec.c:1959 >  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 >  entry_SYSCALL_64_after_hwframe+0x49/0xbe > > The buggy address belongs to the object at ffff8801d4a67d00 >  which belongs to the cache kmalloc-512 of size 512 > The buggy address is located 7 bytes to the right of >  512-byte region [ffff8801d4a67d00, ffff8801d4a67f00) > The buggy address belongs to the page: > page:ffffea00075299c0 count:1 mapcount:0 mapping:ffff8801dac00940 index:0x0 > flags: 0x2fffc0000000100(slab) > raw: 02fffc0000000100 ffffea0007529988 ffffea0007529a48 ffff8801dac00940 > raw: 0000000000000000 ffff8801d4a67080 0000000100000006 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: >  ffff8801d4a67e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >  ffff8801d4a67e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >> ffff8801d4a67f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >                    ^ >  ffff8801d4a67f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >  ffff8801d4a68000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > ================================================================== > What about : diff --git a/net/core/filter.c b/net/core/filter.c index aecdeba052d3f0ff3d4f0a33ec36891f9738052c..a662f59786bd0677850c1c60a2c92faa6fb6c5bb 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2081,7 +2081,7 @@ BPF_CALL_3(bpf_clone_redirect, struct sk_buff *, skb, u32, ifindex, u64, flags) * here, we need to free the just generated clone to unclone once * again. */ - ret = bpf_try_make_head_writable(skb); + ret = bpf_try_make_head_writable(clone); if (unlikely(ret)) { kfree_skb(clone); return -ENOMEM;