Date:   Sun, 11 Nov 2018 10:24:10 -0800
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+0dbf864d3b52555e8265@...kaller.appspotmail.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        syzkaller-bugs@...glegroups.com, netdev <netdev@...r.kernel.org>
Subject: Re: KASAN: use-after-free Read in update_blocked_averages

On Sun, Nov 11, 2018 at 10:18 AM, syzbot
<syzbot+0dbf864d3b52555e8265@...kaller.appspotmail.com> wrote:
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    12ceaf8864c2 infiniband: nes: Fix more direct skb list acc..
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=15a82783400000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=dcbea7daf3ea3e3e
> dashboard link: https://syzkaller.appspot.com/bug?extid=0dbf864d3b52555e8265
> compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=137ae6d5400000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15dbd77b400000

Looking at the reproducer this looks network related, +netdev

r0 = socket$inet6(0xa, 0x2, 0x0)
connect$inet6(r0, &(0x7f0000000100)={0xa, 0x0, 0x0, @dev, 0x6}, 0x1c)
connect$inet6(r0, &(0x7f0000000580)={0xa, 0x4e22, 0x0, @ipv4={[], [],
@local}}, 0x1c)
sendmmsg(r0, &(0x7f00000092c0), 0x4ff, 0x0)


> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+0dbf864d3b52555e8265@...kaller.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: use-after-free in skip_blocked_update kernel/sched/fair.c:3324
> [inline]
> BUG: KASAN: use-after-free in update_blocked_averages+0x1533/0x1e00
> kernel/sched/fair.c:7400
> kasan: CONFIG_KASAN_INLINE enabled
> Read of size 8 at addr ffff8801bf0d6ea0 by task syz-executor841/6015
>
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> CPU: 1 PID: 6015 Comm: syz-executor841 Not tainted 4.20.0-rc1+ #289
> general protection fault: 0000 [#1] PREEMPT SMP KASAN
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> CPU: 0 PID: 6272 Comm: syz-executor841 Not tainted 4.20.0-rc1+ #289
> Call Trace:
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x244/0x39d lib/dump_stack.c:113
> RIP: 0010:vmalloc_fault+0x426/0x770 arch/x86/mm/fault.c:405
> Code: e0 e8 fe 25 47 00 48 b8 00 00 00 00 00 88 ff ff 48 ba 00 00 00 00 00
> fc ff df 48 01 c3 4d 21 e5 4c 01 eb 48 89 d9 48 c1 e9 03 <80> 3c 11 00 0f 85
> b2 02 00 00 48 8b 1b 31 ff 49 89 dc 49 83 e4 9f
> RSP: 0018:ffff8801d9d624c8 EFLAGS: 00010002
> RAX: ffff880000000000 RBX: 000f100180000040 RCX: 0001e20030000008
>  print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256
> RDX: dffffc0000000000 RSI: ffffffff813864c2 RDI: 0000000000000007
>  kasan_report_error mm/kasan/report.c:354 [inline]
>  kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412
> RBP: ffff8801d9d624f8 R08: ffff8801bbb56700 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 000fffffc0000000
>  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
> R13: 000f880180000000 R14: ffffc90001159838 R15: 1ffffffff12a3f98
>  skip_blocked_update kernel/sched/fair.c:3324 [inline]
>  update_blocked_averages+0x1533/0x1e00 kernel/sched/fair.c:7400
> FS:  0000000001f7d880(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffc90001159838 CR3: 00000001ba705000 CR4: 00000000001406f0
> Call Trace:
> Modules linked in:
> ---[ end trace f6450057874cc9c7 ]---
> RIP: 0010:vmalloc_fault+0x426/0x770 arch/x86/mm/fault.c:405
> Code: e0 e8 fe 25 47 00 48 b8 00 00 00 00 00 88 ff ff 48 ba 00 00 00 00 00
> fc ff df 48 01 c3 4d 21 e5 4c 01 eb 48 89 d9 48 c1 e9 03 <80> 3c 11 00 0f 85
> b2 02 00 00 48 8b 1b 31 ff 49 89 dc 49 83 e4 9f
> RSP: 0018:ffff8801d9d624c8 EFLAGS: 00010002
> RAX: ffff880000000000 RBX: 000f100180000040 RCX: 0001e20030000008
> RDX: dffffc0000000000 RSI: ffffffff813864c2 RDI: 0000000000000007
> RBP: ffff8801d9d624f8 R08: ffff8801bbb56700 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 000fffffc0000000
> R13: 000f880180000000 R14: ffffc90001159838 R15: 1ffffffff12a3f98
> FS:  0000000001f7d880(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffc90001159838 CR3: 00000001ba705000 CR4: 00000000001406f0
>
>
> ---
> 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 can test patches for this bug, for details see:
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>
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