Message-ID: <923aa28e-0571-8b65-9132-367cefa994fe@lab.ntt.co.jp>
Date:   Fri, 13 Apr 2018 17:28:03 +0900
From:   Toshiaki Makita <makita.toshiaki@....ntt.co.jp>
To:     Dmitry Vyukov <dvyukov@...gle.com>,
        syzbot <syzbot+0bbe42c764feafa82c5a@...kaller.appspotmail.com>
Cc:     bpoirier@...e.com, David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        "Reshetova, Elena" <elena.reshetova@...el.com>,
        Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mike Maloney <maloney@...gle.com>,
        netdev <netdev@...r.kernel.org>, rami.rosen@...el.com,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: Re: KMSAN: uninit-value in netif_skb_features

On 2018/04/12 17:03, Dmitry Vyukov wrote:
> On Thu, Apr 12, 2018 at 10:01 AM, syzbot
> <syzbot+0bbe42c764feafa82c5a@...kaller.appspotmail.com> wrote:
>> Hello,
>>
>> syzbot hit the following crash on https://github.com/google/kmsan.git/master
>> commit
>> e2ab7e8abba47a2f2698216258e5d8727ae58717 (Fri Apr 6 16:24:31 2018 +0000)
>> kmsan: temporarily disable visitAsmInstruction() to help syzbot
>> syzbot dashboard link:
>> https://syzkaller.appspot.com/bug?extid=0bbe42c764feafa82c5a
>>
>> So far this crash happened 30 times on
>> https://github.com/google/kmsan.git/master.
>> C reproducer: https://syzkaller.appspot.com/x/repro.c?id=4850744041668608
>> syzkaller reproducer:
>> https://syzkaller.appspot.com/x/repro.syz?id=6289386287136768
>> Raw console output:
>> https://syzkaller.appspot.com/x/log.txt?id=4577411249209344
>> Kernel config:
>> https://syzkaller.appspot.com/x/.config?id=6627248707860932248
>> compiler: clang version 7.0.0 (trunk 329391)
> 
> +Toshiaki as this seems to be related to the recent vlan tagging changes.

Seems not.
Probably skb_vlan_tagged_multi() needs to call pskb_may_pull() before
accessing skb->data? I'll confirm it later.

> This also seems to be related to
> https://groups.google.com/d/msg/syzkaller-bugs/FNEavkB4QaM/efXl2AeRBgAJ
> 
> 
> 
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+0bbe42c764feafa82c5a@...kaller.appspotmail.com
>> It will help syzbot understand when the bug is fixed. See footer for
>> details.
>> If you forward the report, please keep this part and the footer.
>>
>> ==================================================================
>> BUG: KMSAN: uninit-value in eth_type_vlan include/linux/if_vlan.h:283
>> [inline]
>> BUG: KMSAN: uninit-value in skb_vlan_tagged_multi
>> include/linux/if_vlan.h:656 [inline]
>> BUG: KMSAN: uninit-value in vlan_features_check include/linux/if_vlan.h:672
>> [inline]
>> BUG: KMSAN: uninit-value in dflt_features_check net/core/dev.c:2949 [inline]
>> BUG: KMSAN: uninit-value in netif_skb_features+0xd1b/0xdc0
>> net/core/dev.c:3009
>> CPU: 1 PID: 3582 Comm: syzkaller435149 Not tainted 4.16.0+ #82
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>> Google 01/01/2011
>> Call Trace:
>>  __dump_stack lib/dump_stack.c:17 [inline]
>>  dump_stack+0x185/0x1d0 lib/dump_stack.c:53
>>  kmsan_report+0x142/0x240 mm/kmsan/kmsan.c:1067
>>  __msan_warning_32+0x6c/0xb0 mm/kmsan/kmsan_instr.c:676
>>  eth_type_vlan include/linux/if_vlan.h:283 [inline]
>>  skb_vlan_tagged_multi include/linux/if_vlan.h:656 [inline]
>>  vlan_features_check include/linux/if_vlan.h:672 [inline]
>>  dflt_features_check net/core/dev.c:2949 [inline]
>>  netif_skb_features+0xd1b/0xdc0 net/core/dev.c:3009
>>  validate_xmit_skb+0x89/0x1320 net/core/dev.c:3084
>>  __dev_queue_xmit+0x1cb2/0x2b60 net/core/dev.c:3549
>>  dev_queue_xmit+0x4b/0x60 net/core/dev.c:3590
>>  packet_snd net/packet/af_packet.c:2944 [inline]
>>  packet_sendmsg+0x7c57/0x8a10 net/packet/af_packet.c:2969
>>  sock_sendmsg_nosec net/socket.c:630 [inline]
>>  sock_sendmsg net/socket.c:640 [inline]
>>  sock_write_iter+0x3b9/0x470 net/socket.c:909
>>  do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
>>  do_iter_write+0x30d/0xd40 fs/read_write.c:932
>>  vfs_writev fs/read_write.c:977 [inline]
>>  do_writev+0x3c9/0x830 fs/read_write.c:1012
>>  SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
>>  SyS_writev+0x56/0x80 fs/read_write.c:1082
>>  do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
>>  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
>> RIP: 0033:0x43ffa9
>> RSP: 002b:00007fff2cff3948 EFLAGS: 00000217 ORIG_RAX: 0000000000000014
>> RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043ffa9
>> RDX: 0000000000000001 RSI: 0000000020000080 RDI: 0000000000000003
>> RBP: 00000000006cb018 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000217 R12: 00000000004018d0
>> R13: 0000000000401960 R14: 0000000000000000 R15: 0000000000000000
>>
>> Uninit was created at:
>>  kmsan_save_stack_with_flags mm/kmsan/kmsan.c:278 [inline]
>>  kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:188
>>  kmsan_kmalloc+0x94/0x100 mm/kmsan/kmsan.c:314
>>  kmsan_slab_alloc+0x11/0x20 mm/kmsan/kmsan.c:321
>>  slab_post_alloc_hook mm/slab.h:445 [inline]
>>  slab_alloc_node mm/slub.c:2737 [inline]
>>  __kmalloc_node_track_caller+0xaed/0x11c0 mm/slub.c:4369
>>  __kmalloc_reserve net/core/skbuff.c:138 [inline]
>>  __alloc_skb+0x2cf/0x9f0 net/core/skbuff.c:206
>>  alloc_skb include/linux/skbuff.h:984 [inline]
>>  alloc_skb_with_frags+0x1d4/0xb20 net/core/skbuff.c:5234
>>  sock_alloc_send_pskb+0xb56/0x1190 net/core/sock.c:2085
>>  packet_alloc_skb net/packet/af_packet.c:2803 [inline]
>>  packet_snd net/packet/af_packet.c:2894 [inline]
>>  packet_sendmsg+0x6444/0x8a10 net/packet/af_packet.c:2969
>>  sock_sendmsg_nosec net/socket.c:630 [inline]
>>  sock_sendmsg net/socket.c:640 [inline]
>>  sock_write_iter+0x3b9/0x470 net/socket.c:909
>>  do_iter_readv_writev+0x7bb/0x970 include/linux/fs.h:1776
>>  do_iter_write+0x30d/0xd40 fs/read_write.c:932
>>  vfs_writev fs/read_write.c:977 [inline]
>>  do_writev+0x3c9/0x830 fs/read_write.c:1012
>>  SYSC_writev+0x9b/0xb0 fs/read_write.c:1085
>>  SyS_writev+0x56/0x80 fs/read_write.c:1082
>>  do_syscall_64+0x309/0x430 arch/x86/entry/common.c:287
>>  entry_SYSCALL_64_after_hwframe+0x3d/0xa2
>> ==================================================================
>>
>>
>> ---
>> This bug is generated by a dumb bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for details.
>> Direct all questions to syzkaller@...glegroups.com.
>>
>> syzbot will keep track of this bug report.
>> If you forgot to add the Reported-by tag, once the fix for this bug is
>> merged
>> into any tree, please reply to this email with:
>> #syz fix: exact-commit-title
>> If you want to test a patch for this bug, please reply with:
>> #syz test: git://repo/address.git branch
>> and provide the patch inline or as an attachment.
>> To mark this as a duplicate of another syzbot report, please reply with:
>> #syz dup: exact-subject-of-another-report
>> If it's a one-off invalid bug report, please reply with:
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>> Note: if the crash happens again, it will cause creation of a new bug
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> 
> 

-- 
Toshiaki Makita

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