Re: [syzbot] general protection fault in dev_get_by_index_rcu (2)

[Alexei Starovoitov <alexei.starovoitov@gmail.com>]

Toke, Jesper,

please take a look.
Seems to be in your area of expertise.

Thanks

On Fri, Jan 7, 2022 at 6:19 AM syzbot
<syzbot+983941aa85af6ded1fd9@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    819d11507f66 bpf, selftests: Fix spelling mistake "tained"..
> git tree:       bpf
> console output: https://syzkaller.appspot.com/x/log.txt?x=12500db3b00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=22b66456935ee10
> dashboard link: https://syzkaller.appspot.com/bug?extid=983941aa85af6ded1fd9
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=153a6cb3b00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=121c690bb00000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+983941aa85af6ded1fd9@syzkaller.appspotmail.com
>
> general protection fault, probably for non-canonical address 0xdffffc000000003e: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x00000000000001f0-0x00000000000001f7]
> CPU: 1 PID: 19 Comm: ksoftirqd/1 Not tainted 5.16.0-rc5-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:dev_index_hash net/core/dev.c:222 [inline]
> RIP: 0010:dev_get_by_index_rcu+0x28/0x140 net/core/dev.c:885
> Code: 00 00 41 55 41 54 55 89 f5 53 48 89 fb e8 00 9d 4d fa 48 8d bb f0 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 fc 00 00 00 48 8b 93 f0 01 00 00 40 0f b6 c5 48
> RSP: 0018:ffffc90000d97608 EFLAGS: 00010202
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000100
> RDX: 000000000000003e RSI: ffffffff872a14d0 RDI: 00000000000001f0
> RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000001
> R10: ffffffff873745ad R11: 000000000008808a R12: ffff88806a062100
> R13: 0000000000000003 R14: ffff88806a062100 R15: ffffc90001116000
> FS:  0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000055555733a848 CR3: 000000001479e000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  ____bpf_clone_redirect net/core/filter.c:2410 [inline]
>  bpf_clone_redirect+0x91/0x420 net/core/filter.c:2401
>  bpf_prog_bebbfe2050753572+0x56/0xcc0
>  __bpf_prog_run include/linux/filter.h:626 [inline]
>  bpf_prog_run_xdp include/linux/filter.h:801 [inline]
>  veth_xdp_rcv_skb+0x64b/0x1b20 drivers/net/veth.c:775
>  veth_xdp_rcv+0x3ac/0x810 drivers/net/veth.c:881
>  veth_poll+0x134/0x850 drivers/net/veth.c:913
>  __napi_poll+0xaf/0x440 net/core/dev.c:7023
>  napi_poll net/core/dev.c:7090 [inline]
>  net_rx_action+0x801/0xb40 net/core/dev.c:7177
>  __do_softirq+0x29b/0x9c2 kernel/softirq.c:558
>  run_ksoftirqd kernel/softirq.c:921 [inline]
>  run_ksoftirqd+0x2d/0x60 kernel/softirq.c:913
>  smpboot_thread_fn+0x645/0x9c0 kernel/smpboot.c:164
>  kthread+0x405/0x4f0 kernel/kthread.c:327
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
>  </TASK>
> Modules linked in:
> ---[ end trace 86b7d5782a67ad32 ]---
> RIP: 0010:dev_index_hash net/core/dev.c:222 [inline]
> RIP: 0010:dev_get_by_index_rcu+0x28/0x140 net/core/dev.c:885
> Code: 00 00 41 55 41 54 55 89 f5 53 48 89 fb e8 00 9d 4d fa 48 8d bb f0 01 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 85 fc 00 00 00 48 8b 93 f0 01 00 00 40 0f b6 c5 48
> RSP: 0018:ffffc90000d97608 EFLAGS: 00010202
> RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000100
> RDX: 000000000000003e RSI: ffffffff872a14d0 RDI: 00000000000001f0
> RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000001
> R10: ffffffff873745ad R11: 000000000008808a R12: ffff88806a062100
> R13: 0000000000000003 R14: ffff88806a062100 R15: ffffc90001116000
> FS:  0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000055555733a848 CR3: 000000001479e000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess):
>    0:   00 00                   add    %al,(%rax)
>    2:   41 55                   push   %r13
>    4:   41 54                   push   %r12
>    6:   55                      push   %rbp
>    7:   89 f5                   mov    %esi,%ebp
>    9:   53                      push   %rbx
>    a:   48 89 fb                mov    %rdi,%rbx
>    d:   e8 00 9d 4d fa          callq  0xfa4d9d12
>   12:   48 8d bb f0 01 00 00    lea    0x1f0(%rbx),%rdi
>   19:   48 b8 00 00 00 00 00    movabs $0xdffffc0000000000,%rax
>   20:   fc ff df
>   23:   48 89 fa                mov    %rdi,%rdx
>   26:   48 c1 ea 03             shr    $0x3,%rdx
> * 2a:   80 3c 02 00             cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
>   2e:   0f 85 fc 00 00 00       jne    0x130
>   34:   48 8b 93 f0 01 00 00    mov    0x1f0(%rbx),%rdx
>   3b:   40 0f b6 c5             movzbl %bpl,%eax
>   3f:   48                      rex.W
>
>
> ---
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