Date:   Fri, 7 Sep 2018 17:19:32 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+a3c9d2673837ccc0f22b@...kaller.appspotmail.com>,
        Kees Cook <keescook@...gle.com>
Cc:     "H. Peter Anvin" <hpa@...or.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: BUG: bad usercopy in __check_object_size (2)

On Fri, Sep 7, 2018 at 5:17 PM, syzbot
<syzbot+a3c9d2673837ccc0f22b@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    28619527b8a7 Merge git://git.kernel.org/pub/scm/linux/kern..
> git tree:       bpf
> console output: https://syzkaller.appspot.com/x/log.txt?x=1618ac21400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=62e9b447c16085cf
> dashboard link: https://syzkaller.appspot.com/bug?extid=a3c9d2673837ccc0f22b
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
>
> Unfortunately, I don't have any reproducer for this crash yet.
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+a3c9d2673837ccc0f22b@...kaller.appspotmail.com

+Kees, looks like false positive?

>  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x457099
> usercopy: Kernel memory overwrite attempt detected to spans multiple pages
> (offset 0, size 64)!
> ------------[ cut here ]------------
> kernel BUG at mm/usercopy.c:102!
> invalid opcode: 0000 [#1] PREEMPT SMP KASAN
> CPU: 0 PID: 15327 Comm: syz-executor2 Not tainted 4.19.0-rc2+ #50
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:usercopy_abort+0xbb/0xbd mm/usercopy.c:90
> Code: c0 e8 8a 23 b2 ff 48 8b 55 c0 49 89 d9 4d 89 f0 ff 75 c8 4c 89 e1 4c
> 89 ee 48 c7 c7 80 48 15 88 ff 75 d0 41 57 e8 5a 38 98 ff <0f> 0b e8 5f 23 b2
> ff e8 8a 6e f5 ff 8b 95 5c fe ff ff 4d 89 e0 31
> RSP: 0018:ffff88019c5ced40 EFLAGS: 00010082
> RAX: 000000000000005f RBX: ffffffff881545a0 RCX: ffffc9000728f000
> RDX: 0000000000000000 RSI: ffffffff8164f825 RDI: 0000000000000005
> RBP: ffff88019c5ced98 R08: ffff8801a3dd23c0 R09: ffffed003b5c3ee2
> R10: ffffed003b5c3ee2 R11: ffff8801dae1f717 R12: ffffffff88154ac0
> R13: ffffffff881546e0 R14: ffffffff881545a0 R15: ffffffff881545a0
> FS:  00007ff971688700(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000001b2cb25000 CR3: 00000001d38c1000 CR4: 00000000001406f0
> DR0: 00000000200001c0 DR1: 0000000020000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
> Call Trace:
>  check_page_span mm/usercopy.c:212 [inline]
>  check_heap_object mm/usercopy.c:241 [inline]
>  __check_object_size.cold.2+0x23/0x134 mm/usercopy.c:266
>  check_object_size include/linux/thread_info.h:119 [inline]
>  __copy_from_user_inatomic include/linux/uaccess.h:65 [inline]
>  __probe_kernel_read+0xda/0x1c0 mm/maccess.c:33
>  show_opcodes+0x4c/0x70 arch/x86/kernel/dumpstack.c:109
>  show_ip+0x31/0x36 arch/x86/kernel/dumpstack.c:126
>  show_iret_regs+0x14/0x38 arch/x86/kernel/dumpstack.c:131
>  __show_regs+0x1c/0x60 arch/x86/kernel/process_64.c:72
>  show_regs_if_on_stack.constprop.10+0x36/0x39
> arch/x86/kernel/dumpstack.c:149
>  show_trace_log_lvl+0x25d/0x28c arch/x86/kernel/dumpstack.c:274
>  show_stack+0x38/0x3a arch/x86/kernel/dumpstack.c:293
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x1c4/0x2b4 lib/dump_stack.c:113
>  fail_dump lib/fault-inject.c:51 [inline]
>  should_fail.cold.4+0xa/0x17 lib/fault-inject.c:149
>  __should_failslab+0x124/0x180 mm/failslab.c:32
>  should_failslab+0x9/0x14 mm/slab_common.c:1557
>  slab_pre_alloc_hook mm/slab.h:423 [inline]
>  slab_alloc_node mm/slab.c:3299 [inline]
>  kmem_cache_alloc_node_trace+0x5a/0x740 mm/slab.c:3661
>  __do_kmalloc_node mm/slab.c:3681 [inline]
>  __kmalloc_node_track_caller+0x33/0x70 mm/slab.c:3696
>  __kmalloc_reserve.isra.39+0x41/0xe0 net/core/skbuff.c:137
>  __alloc_skb+0x155/0x770 net/core/skbuff.c:205
>  alloc_skb_fclone include/linux/skbuff.h:1037 [inline]
>  tipc_buf_acquire+0x2d/0xf0 net/tipc/msg.c:66
>  named_prepare_buf+0x8d/0x4b0 net/tipc/name_distr.c:71
>  tipc_named_publish+0x433/0xa80 net/tipc/name_distr.c:99
>  tipc_nametbl_publish+0x702/0xbb0 net/tipc/name_table.c:630
>  tipc_sk_publish+0x236/0x530 net/tipc/socket.c:2604
>  tipc_sk_join net/tipc/socket.c:2779 [inline]
>  tipc_setsockopt+0x613/0xd70 net/tipc/socket.c:2883
>  __sys_setsockopt+0x1ba/0x3c0 net/socket.c:1900
>  __do_sys_setsockopt net/socket.c:1911 [inline]
>  __se_sys_setsockopt net/socket.c:1908 [inline]
>  __x64_sys_setsockopt+0xbe/0x150 net/socket.c:1908
>  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x457099
> Code: fd b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7
> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff
> 0f 83 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007ff971687c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
> RAX: ffffffffffffffda RBX: 00007ff9716886d4 RCX: 0000000000457099
> RDX: 0000000000000087 RSI: 000000000000010f RDI: 0000000000000006
> RBP: 0000000000930140 R08: 000000000000013f R09: 0000000000000000
> R10: 0000000020000180 R11: 0000000000000246 R12: 0000000000000005
> R13: 00000000004d6570 R14: 00000000004c9ad7 R15: 0000000000000009
> Modules linked in:
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> ---[ end trace d7af0d687a56e2e0 ]---
> RIP: 0010:usercopy_abort+0xbb/0xbd mm/usercopy.c:90
> Code: c0 e8 8a 23 b2 ff 48 8b 55 c0 49 89 d9 4d 89 f0 ff 75 c8 4c 89 e1 4c
> 89 ee 48 c7 c7 80 48 15 88 ff 75 d0 41 57 e8 5a 38 98 ff <0f> 0b e8 5f 23 b2
> ff e8 8a 6e f5 ff 8b 95 5c fe ff ff 4d 89 e0 31
> RSP: 0018:ffff88019c5ced40 EFLAGS: 00010082
> RAX: 000000000000005f RBX: ffffffff881545a0 RCX: ffffc9000728f000
> RDX: 0000000000000000 RSI: ffffffff8164f825 RDI: 0000000000000005
> RBP: ffff88019c5ced98 R08: ffff8801a3dd23c0 R09: ffffed003b5c3ee2
> R10: ffffed003b5c3ee2 R11: ffff8801dae1f717 R12: ffffffff88154ac0
> R13: ffffffff881546e0 R14: ffffffff881545a0 R15: ffffffff881545a0
> FS:  00007ff971688700(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000001b2cb25000 CR3: 00000001d38c1000 CR4: 00000000001406f0
> DR0: 00000000200001c0 DR1: 0000000020000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
>
>
> ---
> 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@...glegroups.com.
>
> syzbot will keep track of this bug report. See:
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> syzbot.
>
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