Re: [syzbot] [net?] KMSAN: uninit-value in erspan_build_header (2)

[Eric Dumazet]

On Fri, Mar 22, 2024 at 1:17 PM syzbot
<syzbot+9e27778c0edc62cb97d8@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    a4145ce1e7bc Merge tag 'bcachefs-2024-03-19' of https://ev..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=154a06a5180000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=5c1d7ee7e74661a8
> dashboard link: https://syzkaller.appspot.com/bug?extid=9e27778c0edc62cb97d8
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1126e1a5180000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15c14e31180000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/ce90c7e9c4b9/disk-a4145ce1.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/fc2e82754c55/vmlinux-a4145ce1.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/dfc8b656ea07/bzImage-a4145ce1.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+9e27778c0edc62cb97d8@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> =====================================================
> BUG: KMSAN: uninit-value in erspan_build_header+0x170/0x2f0 include/net/erspan.h:197
>  erspan_build_header+0x170/0x2f0 include/net/erspan.h:197
>  erspan_xmit+0x128a/0x1ec0 net/ipv4/ip_gre.c:706
>  __netdev_start_xmit include/linux/netdevice.h:4903 [inline]
>  netdev_start_xmit include/linux/netdevice.h:4917 [inline]
>  xmit_one net/core/dev.c:3531 [inline]
>  dev_hard_start_xmit+0x247/0xa20 net/core/dev.c:3547
>  sch_direct_xmit+0x3c5/0xd50 net/sched/sch_generic.c:343
>  __dev_xmit_skb net/core/dev.c:3760 [inline]
>  __dev_queue_xmit+0x2e6a/0x52c0 net/core/dev.c:4301
>  dev_queue_xmit include/linux/netdevice.h:3091 [inline]
>  __bpf_tx_skb net/core/filter.c:2136 [inline]
>  __bpf_redirect_common net/core/filter.c:2180 [inline]
>  __bpf_redirect+0x14a6/0x1620 net/core/filter.c:2187
>  ____bpf_clone_redirect net/core/filter.c:2460 [inline]
>  bpf_clone_redirect+0x328/0x470 net/core/filter.c:2432
>  ___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:1997
>  __bpf_prog_run512+0xb5/0xe0 kernel/bpf/core.c:2238
>  bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
>  __bpf_prog_run include/linux/filter.h:657 [inline]
>  bpf_prog_run include/linux/filter.h:664 [inline]
>  bpf_test_run+0x499/0xc30 net/bpf/test_run.c:425
>  bpf_prog_test_run_skb+0x14ea/0x1f20 net/bpf/test_run.c:1058
>  bpf_prog_test_run+0x6b7/0xad0 kernel/bpf/syscall.c:4240
>  __sys_bpf+0x6aa/0xd90 kernel/bpf/syscall.c:5649
>  __do_sys_bpf kernel/bpf/syscall.c:5738 [inline]
>  __se_sys_bpf kernel/bpf/syscall.c:5736 [inline]
>  __x64_sys_bpf+0xa0/0xe0 kernel/bpf/syscall.c:5736
>  do_syscall_64+0xd5/0x1f0
>  entry_SYSCALL_64_after_hwframe+0x6d/0x75
>
> Uninit was created at:
>  slab_post_alloc_hook mm/slub.c:3804 [inline]
>  slab_alloc_node mm/slub.c:3845 [inline]
>  kmem_cache_alloc_node+0x613/0xc50 mm/slub.c:3888
>  kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:577
>  pskb_expand_head+0x222/0x19d0 net/core/skbuff.c:2245
>  __skb_cow include/linux/skbuff.h:3671 [inline]
>  skb_cow_head include/linux/skbuff.h:3705 [inline]
>  erspan_xmit+0xb08/0x1ec0 net/ipv4/ip_gre.c:692
>  __netdev_start_xmit include/linux/netdevice.h:4903 [inline]
>  netdev_start_xmit include/linux/netdevice.h:4917 [inline]
>  xmit_one net/core/dev.c:3531 [inline]
>  dev_hard_start_xmit+0x247/0xa20 net/core/dev.c:3547
>  sch_direct_xmit+0x3c5/0xd50 net/sched/sch_generic.c:343
>  __dev_xmit_skb net/core/dev.c:3760 [inline]
>  __dev_queue_xmit+0x2e6a/0x52c0 net/core/dev.c:4301
>  dev_queue_xmit include/linux/netdevice.h:3091 [inline]
>  __bpf_tx_skb net/core/filter.c:2136 [inline]
>  __bpf_redirect_common net/core/filter.c:2180 [inline]
>  __bpf_redirect+0x14a6/0x1620 net/core/filter.c:2187
>  ____bpf_clone_redirect net/core/filter.c:2460 [inline]
>  bpf_clone_redirect+0x328/0x470 net/core/filter.c:2432
>  ___bpf_prog_run+0x13fe/0xe0f0 kernel/bpf/core.c:1997
>  __bpf_prog_run512+0xb5/0xe0 kernel/bpf/core.c:2238
>  bpf_dispatcher_nop_func include/linux/bpf.h:1234 [inline]
>  __bpf_prog_run include/linux/filter.h:657 [inline]
>  bpf_prog_run include/linux/filter.h:664 [inline]
>  bpf_test_run+0x499/0xc30 net/bpf/test_run.c:425
>  bpf_prog_test_run_skb+0x14ea/0x1f20 net/bpf/test_run.c:1058
>  bpf_prog_test_run+0x6b7/0xad0 kernel/bpf/syscall.c:4240
>  __sys_bpf+0x6aa/0xd90 kernel/bpf/syscall.c:5649
>  __do_sys_bpf kernel/bpf/syscall.c:5738 [inline]
>  __se_sys_bpf kernel/bpf/syscall.c:5736 [inline]
>  __x64_sys_bpf+0xa0/0xe0 kernel/bpf/syscall.c:5736
>  do_syscall_64+0xd5/0x1f0
>  entry_SYSCALL_64_after_hwframe+0x6d/0x75
>
> CPU: 0 PID: 5041 Comm: syz-executor167 Not tainted 6.8.0-syzkaller-11743-ga4145ce1e7bc #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
> =====================================================
>
>
> ---
> 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@xxxxxxxxxxxxxxxx.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup

Patch sent for review :
https://patchwork.kernel.org/project/netdevbpf/patch/20240322122407.1329861-1-edumazet@xxxxxxxxxx/