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Date:   Mon, 17 Oct 2022 14:08:06 -0700
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Subject: Re: [syzbot] KMSAN: uninit-value in erspan_build_header
From:   sdf@google.com
To:     Jakub Kicinski <kuba@kernel.org>
Cc:     syzbot <syzbot+d551178aab6a783dc249@syzkaller.appspotmail.com>,
        davem@davemloft.net, dsahern@kernel.org, edumazet@google.com,
        glider@google.com, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, pabeni@redhat.com,
        syzkaller-bugs@googlegroups.com, yoshfuji@linux-ipv6.org,
        bpf@vger.kernel.org, yuehaibing@huawei.com,
        Lorenz Bauer <oss@lmb.io>
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Precedence: bulk

On 10/17, Jakub Kicinski wrote:
> CC: bpf, looks like we have a packet with uninitialized payload
> generated by BPF_PROG_TEST_RUN?

Sounds similar to [0] and [1].

0:  
https://lore.kernel.org/bpf/ce5d58a3-32ed-fa81-d490-ce854cfca927@huawei.com/T/#t
1:  
https://lore.kernel.org/bpf/CAKH8qBugSdWHP7mtNxrnLLR+56u_0OCx3xQOkJSV-+RUvDAeNg@mail.gmail.com/T/#t

> On Wed, 12 Oct 2022 09:59:52 -0700 syzbot wrote:
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    968c2729e576 x86: kmsan: fix comment in kmsan_shadow.c
> > git tree:       https://github.com/google/kmsan.git master
> > console output: https://syzkaller.appspot.com/x/log.txt?x=100cd00c880000
> > kernel config:   
> https://syzkaller.appspot.com/x/.config?x=131312b26465c190
> > dashboard link:  
> https://syzkaller.appspot.com/bug?extid=d551178aab6a783dc249
> > compiler:       clang version 15.0.0  
> (https://github.com/llvm/llvm-project.git  
> 610139d2d9ce6746b3c617fb3e2f7886272d26ff), GNU ld (GNU Binutils for  
> Debian) 2.35.2
> > userspace arch: i386
> >
> > Unfortunately, I don't have any reproducer for this issue yet.
> >
> > Downloadable assets:
> > disk image:  
> https://storage.googleapis.com/syzbot-assets/c78ce21b953f/disk-968c2729.raw.xz
> > vmlinux:  
> https://storage.googleapis.com/syzbot-assets/22868d826804/vmlinux-968c2729.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the  
> commit:
> > Reported-by: syzbot+d551178aab6a783dc249@syzkaller.appspotmail.com
> >
> > =====================================================
> > BUG: KMSAN: uninit-value in erspan_build_header+0x16d/0x330  
> include/net/erspan.h:197
> >  erspan_build_header+0x16d/0x330 include/net/erspan.h:197
> >  erspan_xmit+0x11a2/0x1f00 net/ipv4/ip_gre.c:701
> >  __netdev_start_xmit include/linux/netdevice.h:4819 [inline]
> >  netdev_start_xmit include/linux/netdevice.h:4833 [inline]
> >  xmit_one+0x14e/0x5f0 net/core/dev.c:3590
> >  dev_hard_start_xmit+0xe5/0x370 net/core/dev.c:3606
> >  sch_direct_xmit+0x3f1/0xdb0 net/sched/sch_generic.c:342
> >  __dev_xmit_skb+0xc22/0x1a30 net/core/dev.c:3817
> >  __dev_queue_xmit+0x12cb/0x31f0 net/core/dev.c:4222
> >  dev_queue_xmit include/linux/netdevice.h:3008 [inline]
> >  __bpf_tx_skb net/core/filter.c:2115 [inline]
> >  __bpf_redirect_common net/core/filter.c:2154 [inline]
> >  __bpf_redirect+0x1293/0x13b0 net/core/filter.c:2161
> >  ____bpf_clone_redirect net/core/filter.c:2430 [inline]
> >  bpf_clone_redirect+0x324/0x470 net/core/filter.c:2402
> >  ___bpf_prog_run+0x7ed/0xaee0 kernel/bpf/core.c:1813
> >  __bpf_prog_run512+0xc2/0x110 kernel/bpf/core.c:2038
> >  bpf_dispatcher_nop_func include/linux/bpf.h:903 [inline]
> >  __bpf_prog_run include/linux/filter.h:594 [inline]
> >  bpf_prog_run include/linux/filter.h:601 [inline]
> >  bpf_test_run+0x592/0xd20 net/bpf/test_run.c:402
> >  bpf_prog_test_run_skb+0x1625/0x20b0 net/bpf/test_run.c:1141
> >  bpf_prog_test_run+0x6a0/0x730 kernel/bpf/syscall.c:3620
> >  __sys_bpf+0x88d/0xe70 kernel/bpf/syscall.c:4971
> >  __do_sys_bpf kernel/bpf/syscall.c:5057 [inline]
> >  __se_sys_bpf kernel/bpf/syscall.c:5055 [inline]
> >  __ia32_sys_bpf+0x9c/0xe0 kernel/bpf/syscall.c:5055
> >  do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
> >  __do_fast_syscall_32+0xa2/0x100 arch/x86/entry/common.c:178
> >  do_fast_syscall_32+0x33/0x70 arch/x86/entry/common.c:203
> >  do_SYSENTER_32+0x1b/0x20 arch/x86/entry/common.c:246
> >  entry_SYSENTER_compat_after_hwframe+0x70/0x82
> >
> > Uninit was created at:
> >  slab_post_alloc_hook mm/slab.h:732 [inline]
> >  slab_alloc_node mm/slub.c:3258 [inline]
> >  __kmalloc_node_track_caller+0x814/0x1250 mm/slub.c:4970
> >  kmalloc_reserve net/core/skbuff.c:362 [inline]
> >  pskb_expand_head+0x24a/0x1a80 net/core/skbuff.c:1729
> >  __skb_cow include/linux/skbuff.h:3529 [inline]
> >  skb_cow_head include/linux/skbuff.h:3563 [inline]
> >  erspan_xmit+0xad2/0x1f00 net/ipv4/ip_gre.c:688
> >  __netdev_start_xmit include/linux/netdevice.h:4819 [inline]
> >  netdev_start_xmit include/linux/netdevice.h:4833 [inline]
> >  xmit_one+0x14e/0x5f0 net/core/dev.c:3590
> >  dev_hard_start_xmit+0xe5/0x370 net/core/dev.c:3606
> >  sch_direct_xmit+0x3f1/0xdb0 net/sched/sch_generic.c:342
> >  __dev_xmit_skb+0xc22/0x1a30 net/core/dev.c:3817
> >  __dev_queue_xmit+0x12cb/0x31f0 net/core/dev.c:4222
> >  dev_queue_xmit include/linux/netdevice.h:3008 [inline]
> >  __bpf_tx_skb net/core/filter.c:2115 [inline]
> >  __bpf_redirect_common net/core/filter.c:2154 [inline]
> >  __bpf_redirect+0x1293/0x13b0 net/core/filter.c:2161
> >  ____bpf_clone_redirect net/core/filter.c:2430 [inline]
> >  bpf_clone_redirect+0x324/0x470 net/core/filter.c:2402
> >  ___bpf_prog_run+0x7ed/0xaee0 kernel/bpf/core.c:1813
> >  __bpf_prog_run512+0xc2/0x110 kernel/bpf/core.c:2038
> >  bpf_dispatcher_nop_func include/linux/bpf.h:903 [inline]
> >  __bpf_prog_run include/linux/filter.h:594 [inline]
> >  bpf_prog_run include/linux/filter.h:601 [inline]
> >  bpf_test_run+0x592/0xd20 net/bpf/test_run.c:402
> >  bpf_prog_test_run_skb+0x1625/0x20b0 net/bpf/test_run.c:1141
> >  bpf_prog_test_run+0x6a0/0x730 kernel/bpf/syscall.c:3620
> >  __sys_bpf+0x88d/0xe70 kernel/bpf/syscall.c:4971
> >  __do_sys_bpf kernel/bpf/syscall.c:5057 [inline]
> >  __se_sys_bpf kernel/bpf/syscall.c:5055 [inline]
> >  __ia32_sys_bpf+0x9c/0xe0 kernel/bpf/syscall.c:5055
> >  do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
> >  __do_fast_syscall_32+0xa2/0x100 arch/x86/entry/common.c:178
> >  do_fast_syscall_32+0x33/0x70 arch/x86/entry/common.c:203
> >  do_SYSENTER_32+0x1b/0x20 arch/x86/entry/common.c:246
> >  entry_SYSENTER_compat_after_hwframe+0x70/0x82
> >
> > CPU: 0 PID: 12499 Comm: syz-executor.1 Not tainted  
> 6.0.0-rc5-syzkaller-48543-g968c2729e576 #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> Google 09/22/2022
> > =====================================================
> >
> >
> > ---
> > This report 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 issue. See:
> > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.