Re: general protection fault in free_verifier_state (2)

[Alexei Starovoitov]

On Mon, Jan 8, 2018 at 2:58 AM, syzbot
<syzbot+fa99e24f3c29d269a7d5@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> Hello,
>
> syzkaller hit the following crash on
> 895c0dde398510a5b5ded60e5064c11b94bd30ca
> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
> compiler: gcc (GCC) 7.1.1 20170620
> .config is attached
> Raw console output is attached.
> C reproducer is attached
> syzkaller reproducer is attached. See https://goo.gl/kgGztJ
> for information about syzkaller reproducers
>
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+fa99e24f3c29d269a7d5@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.
>
> RBP: 0000000000000006 R08: 0000000000000002 R09: 00007ffd20003032
> R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
> R13: ffffffffffffffff R14: 656c6c616b7a7973 R15: 0000000000000004
> kasan: CONFIG_KASAN_INLINE enabled
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] SMP KASAN
> Dumping ftrace buffer:
>    (ftrace buffer empty)
> Modules linked in:
> CPU: 0 PID: 3468 Comm: syzkaller619543 Not tainted 4.15.0-rc6-next-20180108+
> #90
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> RIP: 0010:free_func_state kernel/bpf/verifier.c:378 [inline]
> RIP: 0010:free_verifier_state+0x6d/0x130 kernel/bpf/verifier.c:388
> RSP: 0018:ffff8801d48f77b8 EFLAGS: 00010206
> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 1ffff1003b6384a0
> RDX: 0000000000000000 RSI: 0000000000000071 RDI: 0000000000000388
> RBP: ffff8801d48f7800 R08: ffff8801db427d00 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801db1c2500
> R13: dffffc0000000000 R14: ffff8801db1c2500 R15: ffff8801db1c2500
> FS:  000000000254e880(0000) GS:ffff8801db400000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020386000 CR3: 00000001cb32e002 CR4: 00000000001606f0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  is_state_visited kernel/bpf/verifier.c:4414 [inline]
>  do_check+0x2442/0x9760 kernel/bpf/verifier.c:4488
>  bpf_check+0x3087/0x5580 kernel/bpf/verifier.c:5483
>  bpf_prog_load+0xbb2/0x1260 kernel/bpf/syscall.c:1205
>  SYSC_bpf kernel/bpf/syscall.c:1820 [inline]
>  SyS_bpf+0x861/0x32e0 kernel/bpf/syscall.c:1782
>  entry_SYSCALL_64_fastpath+0x23/0x9a

hmm. my patch with the fix got lost somehow.
Will resend.