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Wed, 13 Jun 2018 15:17:02 -0700 (PDT) Date: Wed, 13 Jun 2018 15:17:02 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <0000000000009920d3056e8d57a9@google.com> Subject: KASAN: slab-out-of-bounds Read in bpf_skb_change_head From: syzbot To: ast@kernel.org, daniel@iogearbox.net, davem@davemloft.net, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, syzbot found the following crash on: HEAD commit: 75d4e704fa8d netdev-FAQ: clarify DaveM's position for stab.. git tree: bpf-next console output: https://syzkaller.appspot.com/x/log.txt?x=16bd21af800000 kernel config: https://syzkaller.appspot.com/x/.config?x=a601a80fec461d44 dashboard link: https://syzkaller.appspot.com/bug?extid=567faa843005dda30737 compiler: gcc (GCC) 8.0.1 20180413 (experimental) syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1039185f800000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11e85cff800000 IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+567faa843005dda30737@syzkaller.appspotmail.com random: sshd: uninitialized urandom read (32 bytes read) random: sshd: uninitialized urandom read (32 bytes read) random: sshd: uninitialized urandom read (32 bytes read) random: sshd: uninitialized urandom read (32 bytes read) ================================================================== BUG: KASAN: slab-out-of-bounds in ____bpf_skb_change_head net/core/filter.c:2921 [inline] BUG: KASAN: slab-out-of-bounds in bpf_skb_change_head+0x80c/0x9d0 net/core/filter.c:2917 Read of size 4 at addr ffff8801d94ea680 by task syz-executor991/4551 CPU: 0 PID: 4551 Comm: syz-executor991 Not tainted 4.17.0-rc7+ #38 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+0x1b9/0x294 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+0x242/0x2fe mm/kasan/report.c:412 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432 ____bpf_skb_change_head net/core/filter.c:2921 [inline] bpf_skb_change_head+0x80c/0x9d0 net/core/filter.c:2917 Allocated by task 0: (stack is not available) Freed by task 0: (stack is not available) The buggy address belongs to the object at ffff8801d94ea580 which belongs to the cache skbuff_head_cache of size 232 The buggy address is located 24 bytes to the right of 232-byte region [ffff8801d94ea580, ffff8801d94ea668) The buggy address belongs to the page: page:ffffea0007653a80 count:1 mapcount:0 mapping:ffff8801d94ea080 index:0x0 flags: 0x2fffc0000000100(slab) raw: 02fffc0000000100 ffff8801d94ea080 0000000000000000 000000010000000c raw: ffffea0006b2e720 ffffea00076595e0 ffff8801d9450e40 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8801d94ea580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8801d94ea600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > ffff8801d94ea680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ^ ffff8801d94ea700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff8801d94ea780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ================================================================== --- This bug is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this bug report. See: https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with syzbot. syzbot can test patches for this bug, for details see: https://goo.gl/tpsmEJ#testing-patches