Re: KMSAN: uninit-value in netif_skb_features

From: Toshiaki Makita
Date: Fri Apr 13 2018 - 04:29:10 EST

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In reply to: Dmitry Vyukov: "Re: KMSAN: uninit-value in netif_skb_features"
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On 2018/04/12 17:03, Dmitry Vyukov wrote:
> On Thu, Apr 12, 2018 at 10:01 AM, syzbot
> <syzbot+0bbe42c764feafa82c5a@xxxxxxxxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxxxxxxxxx
>> 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@xxxxxxxxxxxxxxxxx
>>
>> 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:
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>> To mark this as a duplicate of another syzbot report, please reply with:
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>
>

--
Toshiaki Makita

Next message: Johannes Thumshirn: "Re: [PATCH v2] block: do not use interruptible wait anywhere"
Previous message: Peter Zijlstra: "Re: [PATCH 1/7] sched/core: uclamp: add CPU clamp groups accounting"
In reply to: Dmitry Vyukov: "Re: KMSAN: uninit-value in netif_skb_features"
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