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Date:   Thu, 10 Sep 2020 10:02:09 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     syzbot <syzbot+72ff2fa98097767b5a27@...kaller.appspotmail.com>,
        Anant Thazhemadam <anant.thazhemadam@...il.com>,
        B K Karthik <bkkarthik@...u.pes.edu>
Cc:     David Miller <davem@...emloft.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        LKML <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>
Subject: Re: KASAN: use-after-free Read in __xfrm6_tunnel_spi_lookup

On Thu, Sep 10, 2020 at 9:20 AM Anant Thazhemadam
<anant.thazhemadam@...il.com> wrote:
> Looks like this bug is no longer valid. I'm not sure which commit seems to have fixed it. Can this be marked as invalid or closed yet?

You can see on the dashboard (or in mailing list archives) that B K
Karthik tested a patch for this bug in July:
https://syzkaller.appspot.com/bug?extid=72ff2fa98097767b5a27

So perhaps that patch fixes it? Karthik, did you send it? Was it
merged? Did the commit include the syzbot Reported-by tag?



On Thu, Jul 16, 2020 at 4:05 AM syzbot
<syzbot+72ff2fa98097767b5a27@...kaller.appspotmail.com> wrote:
>
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit:    ca0e494a Add linux-next specific files for 20200715
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=175099bf100000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=2c76d72659687242
> dashboard link: https://syzkaller.appspot.com/bug?extid=72ff2fa98097767b5a27
> compiler:       gcc (GCC) 10.1.0-syz 20200507
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=112e8dbf100000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=109429bf100000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+72ff2fa98097767b5a27@...kaller.appspotmail.com
>
> netdevsim netdevsim0 netdevsim1: set [1, 0] type 2 family 0 port 6081 - 0
> netdevsim netdevsim0 netdevsim2: set [1, 0] type 2 family 0 port 6081 - 0
> netdevsim netdevsim0 netdevsim3: set [1, 0] type 2 family 0 port 6081 - 0
> ==================================================================
> BUG: KASAN: use-after-free in __xfrm6_tunnel_spi_lookup+0x3a9/0x3b0 net/ipv6/xfrm6_tunnel.c:79
> Read of size 8 at addr ffff8880934578a8 by task syz-executor437/6811
> CPU: 0 PID: 6811 Comm: syz-executor437 Not tainted 5.8.0-rc5-next-20200715-syzkaller #0
> 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+0x18f/0x20d lib/dump_stack.c:118
>  print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
>  __kasan_report mm/kasan/report.c:513 [inline]
>  kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
>  __xfrm6_tunnel_spi_lookup+0x3a9/0x3b0 net/ipv6/xfrm6_tunnel.c:79
>  xfrm6_tunnel_spi_lookup+0x8a/0x1d0 net/ipv6/xfrm6_tunnel.c:95
>  xfrmi6_rcv_tunnel+0xb9/0x100 net/xfrm/xfrm_interface.c:824
>  tunnel6_rcv+0xef/0x2b0 net/ipv6/tunnel6.c:148
>  ip6_protocol_deliver_rcu+0x2e8/0x1670 net/ipv6/ip6_input.c:433
>  ip6_input_finish+0x7f/0x160 net/ipv6/ip6_input.c:474
>  NF_HOOK include/linux/netfilter.h:307 [inline]
>  NF_HOOK include/linux/netfilter.h:301 [inline]
>  ip6_input+0x9c/0xd0 net/ipv6/ip6_input.c:483
>  dst_input include/net/dst.h:449 [inline]
>  ip6_rcv_finish net/ipv6/ip6_input.c:76 [inline]
>  NF_HOOK include/linux/netfilter.h:307 [inline]
>  NF_HOOK include/linux/netfilter.h:301 [inline]
>  ipv6_rcv+0x28e/0x3c0 net/ipv6/ip6_input.c:307
>  __netif_receive_skb_one_core+0x114/0x180 net/core/dev.c:5287
>  __netif_receive_skb+0x27/0x1c0 net/core/dev.c:5401
>  netif_receive_skb_internal net/core/dev.c:5503 [inline]
>  netif_receive_skb+0x159/0x990 net/core/dev.c:5562
>  tun_rx_batched.isra.0+0x460/0x720 drivers/net/tun.c:1518
>  tun_get_user+0x23b2/0x35b0 drivers/net/tun.c:1972
>  tun_chr_write_iter+0xba/0x151 drivers/net/tun.c:2001
>  call_write_iter include/linux/fs.h:1879 [inline]
>  new_sync_write+0x422/0x650 fs/read_write.c:515
>  vfs_write+0x59d/0x6b0 fs/read_write.c:595
>  ksys_write+0x12d/0x250 fs/read_write.c:648
>  do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x403d50
> Code: Bad RIP value.
> RSP: 002b:00007ffe8fe93368 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000403d50
> RDX: 000000000000005e RSI: 00000000200007c0 RDI: 00000000000000f0
> RBP: 00007ffe8fe93390 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe8fe93380
> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> Allocated by task 6811:
>  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
>  kasan_set_track mm/kasan/common.c:56 [inline]
>  __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
>  __do_kmalloc mm/slab.c:3655 [inline]
>  __kmalloc+0x1a8/0x320 mm/slab.c:3664
>  kmalloc include/linux/slab.h:559 [inline]
>  kzalloc include/linux/slab.h:666 [inline]
>  tomoyo_init_log+0x1335/0x1e50 security/tomoyo/audit.c:275
>  tomoyo_supervisor+0x32f/0xeb0 security/tomoyo/common.c:2097
>  tomoyo_audit_path_number_log security/tomoyo/file.c:235 [inline]
>  tomoyo_path_number_perm+0x3ed/0x4d0 security/tomoyo/file.c:734
>  security_file_ioctl+0x50/0xb0 security/security.c:1489
>  ksys_ioctl+0x50/0x180 fs/ioctl.c:747
>  __do_sys_ioctl fs/ioctl.c:762 [inline]
>  __se_sys_ioctl fs/ioctl.c:760 [inline]
>  __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:760
>  do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> Freed by task 6811:
>  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
>  kasan_set_track+0x1c/0x30 mm/kasan/common.c:56
>  kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355
>  __kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422
>  __cache_free mm/slab.c:3418 [inline]
>  kfree+0x103/0x2c0 mm/slab.c:3756
>  tomoyo_supervisor+0x350/0xeb0 security/tomoyo/common.c:2149
>  tomoyo_audit_path_number_log security/tomoyo/file.c:235 [inline]
>  tomoyo_path_number_perm+0x3ed/0x4d0 security/tomoyo/file.c:734
>  security_file_ioctl+0x50/0xb0 security/security.c:1489
>  ksys_ioctl+0x50/0x180 fs/ioctl.c:747
>  __do_sys_ioctl fs/ioctl.c:762 [inline]
>  __se_sys_ioctl fs/ioctl.c:760 [inline]
>  __x64_sys_ioctl+0x6f/0xb0 fs/ioctl.c:760
>  do_syscall_64+0x60/0xe0 arch/x86/entry/common.c:384
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> The buggy address belongs to the object at ffff888093457800
>  which belongs to the cache kmalloc-512 of size 512
> The buggy address is located 168 bytes inside of
>  512-byte region [ffff888093457800, ffff888093457a00)
> The buggy address belongs to the page:
> page:000000005c2b5911 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x93457
> flags: 0xfffe0000000200(slab)
> raw: 00fffe0000000200 ffffea00028d4308 ffffea0002834c88 ffff8880aa000600
> raw: 0000000000000000 ffff888093457000 0000000100000004 0000000000000000
> page dumped because: kasan: bad access detected
> Memory state around the buggy address:
>  ffff888093457780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>  ffff888093457800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff888093457880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                                   ^
>  ffff888093457900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff888093457980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================

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