Re: bpf-next hang+kasan uaf refcount acquire splat when running test_progs

[Florian Westphal <fw@strlen.de>]

Eduard Zingerman <eddyz87@gmail.com> wrote:
> > BUG: KASAN: slab-out-of-bounds in bpf_refcount_acquire_impl+0x63/0xd0
> > Write of size 4 at addr ffff8881072b34e8 by task new_name/12847
> > 
> > CPU: 1 PID: 12847 Comm: new_name Not tainted 6.3.0-rc6+ #129
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-20220807_005459-localhost 04/01/2014
> > Call Trace:
> >  <TASK>
> >  dump_stack_lvl+0x32/0x40
> >  print_address_description.constprop.0+0x2b/0x3d0
> >  ? bpf_refcount_acquire_impl+0x63/0xd0
> >  print_report+0xb0/0x260
> >  ? bpf_refcount_acquire_impl+0x63/0xd0
> >  ? kasan_addr_to_slab+0x9/0x70
> >  ? bpf_refcount_acquire_impl+0x63/0xd0
> >  kasan_report+0xad/0xd0
> >  ? bpf_refcount_acquire_impl+0x63/0xd0
> >  kasan_check_range+0x13b/0x190
> >  bpf_refcount_acquire_impl+0x63/0xd0
> >  bpf_prog_affcc6c9d58016ca___insert_in_tree_and_list+0x54/0x131
> >  bpf_prog_795203cdef4805f4_insert_and_remove_tree_true_list_true+0x15/0x11b
> >  bpf_test_run+0x2a0/0x5f0
> >  ? bpf_test_timer_continue+0x430/0x430
> >  ? kmem_cache_alloc+0xe5/0x260
> >  ? kasan_set_track+0x21/0x30
> >  ? krealloc+0x9e/0xe0
> >  bpf_prog_test_run_skb+0x890/0x1270
> >  ? __kmem_cache_free+0x9f/0x170
> >  ? bpf_prog_test_run_raw_tp+0x570/0x570
> >  ? __fget_light+0x52/0x4d0
> >  ? map_update_elem+0x680/0x680
> >  __sys_bpf+0x75e/0xd10
> >  ? bpf_link_by_id+0xa0/0xa0
> >  ? rseq_get_rseq_cs+0x67/0x650
> >  ? __blkcg_punt_bio_submit+0x1b0/0x1b0
> >  __x64_sys_bpf+0x6f/0xb0
> >  do_syscall_64+0x3a/0x80
> >  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> > RIP: 0033:0x7f2f6a8b392d
> > Code: 5d c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 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 73 01 c3 48 8b 0d d3 e4 0c 00 f7 d8 64 89 01 48
> > RSP: 002b:00007ffe46938328 EFLAGS: 00000206 ORIG_RAX: 0000000000000141
> > RAX: ffffffffffffffda RBX: 0000000007150690 RCX: 00007f2f6a8b392d
> > RDX: 0000000000000050 RSI: 00007ffe46938360 RDI: 000000000000000a
> > RBP: 00007ffe46938340 R08: 0000000000000064 R09: 00007ffe46938360
> > R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
> > R13: 00007ffe46938b78 R14: 0000000000e09db0 R15: 00007f2f6a9ff000
> >  </TASK>
> > 
> > I can also reproduce this on bpf-next/780c69830ec6b27e0224586ce26bc89552fcf163.
> > Is this a known bug?
> 
> Hi Florian,
> 
> Thank you for the report, that's my bug :(
> 
> After the suggested change I can run the ./test_progs till the end
>  (takes a few minutes, though). One test is failing: verifier_array_access,
> this is because map it uses is not populated with values (as it was when this was
> a part ./test_verifier).

Right, I see that failure too.
> However, in the middle of execution I do see a trace similar to yours:

I see this as well, to get to it quicker:
./test_progs --allow=refcounted_kptr


> [   82.757127] ------------[ cut here ]------------
> [   82.757667] refcount_t: saturated; leaking memory.
> [   82.758098] WARNING: CPU: 0 PID: 176 at lib/refcount.c:22 refcount_warn_saturate+0x61/0xe0

I get this one right after the kasan splat.

> Could you please share your config?
> I'd like to reproduce the hang.

It hangs for me if I just rerun 
./test_progs --allow=refcounted_kptr

a couple of times (maybe once per cpu...?).

I'll send the config if that doesn't hang for you.