Re: WARNING in bpf_raw_tp_link_fill_link_info

[Dmitry Vyukov]

On Fri, Sep 11, 2020 at 12:01 AM Andrii Nakryiko
<andrii.nakryiko@xxxxxxxxx> wrote:
>
> On Thu, Sep 10, 2020 at 2:31 AM syzbot
> <syzbot+976d5ecfab0c7eb43ac3@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    7fb5eefd selftests/bpf: Fix test_sysctl_loop{1, 2} failure..
> > git tree:       bpf-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=1424fdb3900000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=b6856d16f78d8fa9
> > dashboard link: https://syzkaller.appspot.com/bug?extid=976d5ecfab0c7eb43ac3
> > compiler:       gcc (GCC) 10.1.0-syz 20200507
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14a1f411900000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10929c11900000
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+976d5ecfab0c7eb43ac3@xxxxxxxxxxxxxxxxxxxxxxxxx
> >
> > ------------[ cut here ]------------
> > WARNING: CPU: 0 PID: 6854 at include/linux/thread_info.h:150 check_copy_size include/linux/thread_info.h:150 [inline]
> > WARNING: CPU: 0 PID: 6854 at include/linux/thread_info.h:150 copy_to_user include/linux/uaccess.h:167 [inline]
> > WARNING: CPU: 0 PID: 6854 at include/linux/thread_info.h:150 bpf_raw_tp_link_fill_link_info+0x306/0x350 kernel/bpf/syscall.c:2661
> > Kernel panic - not syncing: panic_on_warn set ...
> > CPU: 0 PID: 6854 Comm: syz-executor574 Not tainted 5.9.0-rc1-syzkaller #0
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> > Call Trace:
> >  __dump_stack lib/dump_stack.c:77 [inline]
> >  dump_stack+0x18f/0x20d lib/dump_stack.c:118
> >  panic+0x2e3/0x75c kernel/panic.c:231
> >  __warn.cold+0x20/0x4a kernel/panic.c:600
> >  report_bug+0x1bd/0x210 lib/bug.c:198
> >  handle_bug+0x38/0x90 arch/x86/kernel/traps.c:234
> >  exc_invalid_op+0x14/0x40 arch/x86/kernel/traps.c:254
> >  asm_exc_invalid_op+0x12/0x20 arch/x86/include/asm/idtentry.h:536
> > RIP: 0010:check_copy_size include/linux/thread_info.h:150 [inline]
> > RIP: 0010:copy_to_user include/linux/uaccess.h:167 [inline]
> > RIP: 0010:bpf_raw_tp_link_fill_link_info+0x306/0x350 kernel/bpf/syscall.c:2661
> > Code: 41 bc ea ff ff ff e9 35 ff ff ff 4c 89 ff e8 41 66 33 00 e9 d0 fd ff ff 4c 89 ff e8 a4 66 33 00 e9 06 ff ff ff e8 ca ed f2 ff <0f> 0b eb 94 48 89 ef e8 2e 66 33 00 e9 65 fd ff ff e8 24 66 33 00
> > RSP: 0018:ffffc900051c7bd0 EFLAGS: 00010293
> > RAX: 0000000000000000 RBX: ffffc900051c7c60 RCX: ffffffff818179d6
> > RDX: ffff88808b490000 RSI: ffffffff81817a96 RDI: 0000000000000006
> > RBP: 0000000000000019 R08: 0000000000000000 R09: ffffc900051c7c7f
> > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000019
> > R13: 0000000000001265 R14: ffffffff8986ecc0 R15: ffffc900051c7c78
> >  bpf_link_get_info_by_fd kernel/bpf/syscall.c:3626 [inline]
> >  bpf_obj_get_info_by_fd+0x43a/0xc40 kernel/bpf/syscall.c:3664
> >  __do_sys_bpf+0x1906/0x4b30 kernel/bpf/syscall.c:4237
> >  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
> >  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > RIP: 0033:0x4405f9
> > Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> > RSP: 002b:00007fff47155808 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
> > RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004405f9
> > RDX: 0000000000000010 RSI: 00000000200000c0 RDI: 000000000000000f
> > RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
> > R10: 00000000004002c8 R11: 0000000000000246 R12: 0000000000401e00
> > R13: 0000000000401e90 R14: 0000000000000000 R15: 0000000000000000
> > Kernel Offset: disabled
> > Rebooting in 86400 seconds..
> >
>
> #syz fix: b474959d5afd ("bpf: Fix a buffer out-of-bound access when
> filling raw_tp link_info")

Complete patch title:

#syz fix:
bpf: Fix a buffer out-of-bound access when filling raw_tp link_info