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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Wed, 27 Mar 2019 09:22:29 +0100
Message-ID: <CACT4Y+Yt9vfk1OM1b3fsVJ_i+qZx7kz71ty6heDE3GwujGNevQ@mail.gmail.com>
Subject: Re: KASAN: use-after-free Read in __icmp_send
To:     syzbot <syzbot+aa9105f99c12b6abfe27@syzkaller.appspotmail.com>,
        Eric Dumazet <edumazet@google.com>
Cc:     David Miller <davem@davemloft.net>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        LKML <linux-kernel@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
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Sender: linux-kernel-owner@vger.kernel.org
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On Wed, Mar 27, 2019 at 9:19 AM syzbot
<syzbot+aa9105f99c12b6abfe27@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    1d965c4d Merge branch 'Refactor-flower-classifier-to-remov..
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=14ff71df200000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=f05902bca21d8935
> dashboard link: https://syzkaller.appspot.com/bug?extid=aa9105f99c12b6abfe27
> compiler:       gcc (GCC) 9.0.0 20181231 (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+aa9105f99c12b6abfe27@syzkaller.appspotmail.com

Eric, do you think this is also fixed by "tun: properly test for
IFF_UP" as the bug in icmp6_send?

> ==================================================================
> BUG: KASAN: use-after-free in atomic_read
> include/asm-generic/atomic-instrumented.h:26 [inline]
> BUG: KASAN: use-after-free in queued_spin_trylock
> include/asm-generic/qspinlock.h:69 [inline]
> BUG: KASAN: use-after-free in do_raw_spin_trylock+0x6a/0x180
> kernel/locking/spinlock_debug.c:119
> Read of size 4 at addr ffff88808a28ccd4 by task syz-executor.0/17585
>
> CPU: 0 PID: 17585 Comm: syz-executor.0 Not tainted 5.0.0+ #105
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>   <IRQ>
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x172/0x1f0 lib/dump_stack.c:113
>   print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
>   kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
>   check_memory_region_inline mm/kasan/generic.c:185 [inline]
>   check_memory_region+0x123/0x190 mm/kasan/generic.c:191
>   kasan_check_read+0x11/0x20 mm/kasan/common.c:102
>   atomic_read include/asm-generic/atomic-instrumented.h:26 [inline]
>   queued_spin_trylock include/asm-generic/qspinlock.h:69 [inline]
>   do_raw_spin_trylock+0x6a/0x180 kernel/locking/spinlock_debug.c:119
>   __raw_spin_trylock include/linux/spinlock_api_smp.h:89 [inline]
>   _raw_spin_trylock+0x1c/0x80 kernel/locking/spinlock.c:128
>   spin_trylock include/linux/spinlock.h:339 [inline]
>   icmp_xmit_lock net/ipv4/icmp.c:219 [inline]
>   __icmp_send+0x553/0x1400 net/ipv4/icmp.c:666
>   icmp_send include/net/icmp.h:47 [inline]
>   ipv4_link_failure+0x31/0x210 net/ipv4/route.c:1190
>   dst_link_failure include/net/dst.h:416 [inline]
>   arp_error_report+0xd1/0x1c0 net/ipv4/arp.c:297
>   neigh_invalidate+0x24b/0x570 net/core/neighbour.c:995
>   neigh_timer_handler+0xc35/0xf30 net/core/neighbour.c:1081
>   call_timer_fn+0x190/0x720 kernel/time/timer.c:1325
>   expire_timers kernel/time/timer.c:1362 [inline]
>   __run_timers kernel/time/timer.c:1681 [inline]
>   __run_timers kernel/time/timer.c:1649 [inline]
>   run_timer_softirq+0x652/0x1700 kernel/time/timer.c:1694
>   __do_softirq+0x266/0x95a kernel/softirq.c:293
>   invoke_softirq kernel/softirq.c:374 [inline]
>   irq_exit+0x180/0x1d0 kernel/softirq.c:414
>   exiting_irq arch/x86/include/asm/apic.h:536 [inline]
>   smp_apic_timer_interrupt+0x14a/0x570 arch/x86/kernel/apic/apic.c:1062
>   apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:807
>   </IRQ>
> RIP: 0010:filename_mountpoint+0x25d/0x3c0 fs/namei.c:2722
> Code: 14 02 4c 89 e0 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 1c 01 00 00
> 45 8b 24 24 31 ff 44 89 e6 e8 58 ea ba ff 45 85 e4 74 62 <e8> ce e8 ba ff
> e8 49 2a fe ff 4c 89 f7 e8 81 f2 ff ff e8 bc e8 ba
> RSP: 0018:ffff8880a857fc30 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
> RAX: dffffc0000000000 RBX: 1ffff110150aff88 RCX: ffffffff81b57ad4
> RDX: 1ffff1100bd8e54c RSI: ffffffff81b57ae2 RDI: ffff88805ec72a60
> RBP: ffff8880a857fdc8 R08: ffff88805ec72300 R09: 0000000000000001
> R10: 000000000000001c R11: ffff8880ae82de3b R12: 0000000000000000
> R13: 0000000000000000 R14: ffff888097790e00 R15: ffff8880a857fe68
>   user_path_mountpoint_at+0x3a/0x50 fs/namei.c:2745
>   ksys_umount+0x167/0xf00 fs/namespace.c:1687
>   __do_sys_umount fs/namespace.c:1713 [inline]
>   __se_sys_umount fs/namespace.c:1711 [inline]
>   __x64_sys_umount+0x54/0x80 fs/namespace.c:1711
>   do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x45ac57
> Code: 44 00 00 b8 08 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 4d 8e fb ff c3
> 66 2e 0f 1f 84 00 00 00 00 00 66 90 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff
> ff 0f 83 2d 8e fb ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007ffe6359ff08 EFLAGS: 00000202 ORIG_RAX: 00000000000000a6
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000045ac57
> RDX: 0000000000402ea0 RSI: 0000000000000002 RDI: 00007ffe6359ffb0
> RBP: 00000000000019e0 R08: 0000000000000000 R09: 000000000000000d
> R10: 0000000000000006 R11: 0000000000000202 R12: 00007ffe635a1040
> R13: 0000000000bfa940 R14: 0000000000000000 R15: 00007ffe635a1040
>
> Allocated by task 12478:
>   save_stack+0x45/0xd0 mm/kasan/common.c:75
>   set_track mm/kasan/common.c:87 [inline]
>   __kasan_kmalloc mm/kasan/common.c:497 [inline]
>   __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:470
>   kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:505
>   slab_post_alloc_hook mm/slab.h:436 [inline]
>   slab_alloc mm/slab.c:3392 [inline]
>   kmem_cache_alloc+0x11a/0x6f0 mm/slab.c:3554
>   getname_flags fs/namei.c:138 [inline]
>   getname_flags+0xd6/0x5b0 fs/namei.c:128
>   getname+0x1a/0x20 fs/namei.c:209
>   do_sys_open+0x2c9/0x5d0 fs/open.c:1057
>   __do_sys_open fs/open.c:1081 [inline]
>   __se_sys_open fs/open.c:1076 [inline]
>   __x64_sys_open+0x7e/0xc0 fs/open.c:1076
>   do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> Freed by task 12478:
>   save_stack+0x45/0xd0 mm/kasan/common.c:75
>   set_track mm/kasan/common.c:87 [inline]
>   __kasan_slab_free+0x102/0x150 mm/kasan/common.c:459
>   kasan_slab_free+0xe/0x10 mm/kasan/common.c:467
>   __cache_free mm/slab.c:3498 [inline]
>   kmem_cache_free+0x86/0x260 mm/slab.c:3764
>   putname+0xef/0x130 fs/namei.c:259
>   do_sys_open+0x318/0x5d0 fs/open.c:1072
>   __do_sys_open fs/open.c:1081 [inline]
>   __se_sys_open fs/open.c:1076 [inline]
>   __x64_sys_open+0x7e/0xc0 fs/open.c:1076
>   do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
>
> The buggy address belongs to the object at ffff88808a28c780
>   which belongs to the cache names_cache of size 4096
> The buggy address is located 1364 bytes inside of
>   4096-byte region [ffff88808a28c780, ffff88808a28d780)
> The buggy address belongs to the page:
> page:ffffea000228a300 count:1 mapcount:0 mapping:ffff88812c2d8dc0 index:0x0
> compound_mapcount: 0
> flags: 0x1fffc0000010200(slab|head)
> raw: 01fffc0000010200 ffffea00025c8908 ffffea0001840a08 ffff88812c2d8dc0
> raw: 0000000000000000 ffff88808a28c780 0000000100000001 0000000000000000
> page dumped because: kasan: bad access detected
>
> Memory state around the buggy address:
>   ffff88808a28cb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff88808a28cc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff88808a28cc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                                   ^
>   ffff88808a28cd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>   ffff88808a28cd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
>
>
> ---
> 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#status for how to communicate with syzbot.
>
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