Messages in this thread | | | Date | Tue, 25 Jul 2017 13:43:45 +0300 | From | Hans Liljestrand <> | Subject | Re: [lkp-robot] [x86/refcount] b631e535c6: WARNING:at_net/netlink/af_netlink.c:#netlink_sock_destruct |
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On Mon, Jul 24, 2017 at 08:21:16PM -0700, Kees Cook wrote: >On Mon, Jul 24, 2017 at 6:03 AM, Hans Liljestrand ><liljestrandh@gmail.com> wrote: >> On Sun, Jul 23, 2017 at 08:52:53PM -0700, Kees Cook wrote: >>> >>> Is 14afee4b6092f ("net: convert sock.sk_wmem_alloc from atomic_t to >>> refcount_t") correct? That looks like a statistics counter, not a >>> refcounter? I can't quite tell, though... >> >> >> Hmm, yes, it looks a bit weird, but it is used in a refcount fashion here: >> >> void sk_free(struct sock *sk) >> { >> /* >> * We subtract one from sk_wmem_alloc and can know if >> * some packets are still in some tx queue. >> * If not null, sock_wfree() will call __sk_free(sk) later >> */ >> if (refcount_dec_and_test(&sk->sk_wmem_alloc)) >> __sk_free(sk); >> } >> http://elixir.free-electrons.com/linux/v4.13-rc1/source/net/core/sock.c#L1605 > >Ah yeah, there it is. Hrmpf. Something is triggering WARNs, though... >I wonder if this can get examined more closely?
I tried reproducing the error but I don't seem to know how to use lkp. Got lots of permission denied errors and finally ran out of disk space (after using up ~50GB).
Maybe I did something wrong?
What I did was: Cloned the related kernel repository, checked out offending commit, plopped in config, compiled bzImage. Then I just cloned the lkp repo and tried running the provided command line with the bzImage and provided script.
I'll take another look once I have the time, might be I missed something earlier.
> >Also, why not atomic->refcount for sk_rmem_alloc?
I couldn't find any similar refcount-like use on sk_rmem_alloc.
And as noted the sk_wmem_alloc thing is also a bit dubious. It looks like it serves a dual purpose of actual allocation size and occasional reference counter.
Regards, -hans
> >-Kees > >> >> And here: >> >> if (refcount_sub_and_test(len, &sk->sk_wmem_alloc)) >> __sk_free(sk); >> } >> http://elixir.free-electrons.com/linux/v4.13-rc1/source/net/core/sock.c#L1798 >> >>> >>> I think this WARN is from: >>> >>> WARN_ON(refcount_read(&sk->sk_wmem_alloc)); >> >> >> I looked through the commit and couldn't find any direct conversion issues. >> Although I guess it is debatable whether refcoun_t should be used in this >> kind of less conventional case. >> >> The only potential problem I noticed was that based on the following change >> (or rather the original code) it seems like sk_wmem_alloc could sometimes be >> negative. I'm not familiar enough with the code to say whether that really >> is the case. >> >> --- a/drivers/atm/fore200e.c >> +++ b/drivers/atm/fore200e.c >> @@ -924,12 +924,7 @@ fore200e_tx_irq(struct fore200e* fore200e) >> else { >> dev_kfree_skb_any(entry->skb); >> } >> -#if 1 >> - /* race fixed by the above incarnation mechanism, but... */ >> - if (atomic_read(&sk_atm(vcc)->sk_wmem_alloc) < 0) { >> - atomic_set(&sk_atm(vcc)->sk_wmem_alloc, 0); >> - } >> -#endif >> + >> /* check error condition */ >> if (*entry->status & STATUS_ERROR) >> atomic_inc(&vcc->stats->tx_err); >> >> But if this is actually supposed to legitimately happen and eventually >> "balance out" refcount_t might not work here. On the other hand this should >> have triggered an earlier WARN_ON already, so it doesn't seem to be the >> issue here? >> >> Regards, >> -hans >> >> >>> >>> -Kees >>> >>> On Sun, Jul 23, 2017 at 7:13 PM, kernel test robot >>> <xiaolong.ye@intel.com> wrote: >>>> >>>> >>>> FYI, we noticed the following commit: >>>> >>>> commit: b631e535c61d7ddbb7ebac545f729ca9b3b6d70e ("x86/refcount: >>>> Implement fast refcount overflow protection") >>>> https://git.kernel.org/cgit/linux/kernel/git/kees/linux.git >>>> kspp/fast-refcount/ud/v6 >>>> >>>> in testcase: boot >>>> >>>> on test machine: qemu-system-x86_64 -enable-kvm -smp 2 -m 512M >>>> >>>> caused below changes (please refer to attached dmesg/kmsg for entire >>>> log/backtrace): >>>> >>>> >>>> >>>> +------------------------------------------------------------+------------+------------+ >>>> | | 561ee9566e >>>> | b631e535c6 | >>>> >>>> +------------------------------------------------------------+------------+------------+ >>>> | boot_successes | 37 >>>> | 0 | >>>> | boot_failures | 0 >>>> | 4 | >>>> | WARNING:at_net/netlink/af_netlink.c:#netlink_sock_destruct | 0 >>>> | 4 | >>>> >>>> +------------------------------------------------------------+------------+------------+ >>>> >>>> >>>> >>>> [ 36.991339] WARNING: CPU: 0 PID: 280 at net/netlink/af_netlink.c:374 >>>> netlink_sock_destruct+0x1ea/0x200 >>>> [ 36.994035] Modules linked in: >>>> [ 36.994815] CPU: 0 PID: 280 Comm: sh Not tainted >>>> 4.13.0-rc1-00003-gb631e53 #1 >>>> [ 36.996546] task: ffff88001448c180 task.stack: ffffc900004e0000 >>>> [ 36.998006] RIP: 0010:netlink_sock_destruct+0x1ea/0x200 >>>> [ 36.999290] RSP: 0018:ffffffff82433de0 EFLAGS: 00010206 >>>> [ 37.000591] RAX: ffff88001448c180 RBX: ffff880016a3d000 RCX: >>>> 0000000000000000 >>>> [ 37.002319] RDX: 0000000000000100 RSI: 0000000000000001 RDI: >>>> ffffffff82796f48 >>>> [ 37.004061] RBP: ffffffff82433df0 R08: 0000000000000000 R09: >>>> 0000000000000000 >>>> [ 37.005780] R10: 0000000000000001 R11: 0000000000000001 R12: >>>> 0000000000000001 >>>> [ 37.007528] R13: ffffffff81cd4a00 R14: 96e49674e09954cf R15: >>>> 000000000000001f >>>> [ 37.009261] FS: 0000000000000000(0000) GS:ffffffff82430000(0000) >>>> knlGS:0000000000000000 >>>> [ 37.011233] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>>> [ 37.012629] CR2: 00007f268a96e688 CR3: 00000000159ff000 CR4: >>>> 00000000000006b0 >>>> [ 37.014212] Call Trace: >>>> [ 37.014745] <IRQ> >>>> [ 37.015201] __sk_destruct+0x3a2/0x4c0 >>>> [ 37.015994] sk_destruct+0x3f/0x70 >>>> [ 37.016747] __sk_free+0x10d/0x160 >>>> [ 37.017479] sk_free+0x4a/0x60 >>>> [ 37.018127] deferred_put_nlk_sk+0xd9/0xf0 >>>> [ 37.018998] rcu_process_callbacks+0x766/0x1cb0 >>>> [ 37.019944] ? rcu_process_callbacks+0x643/0x1cb0 >>>> [ 37.020960] __do_softirq+0x10c/0x6b2 >>>> [ 37.021749] irq_exit+0x135/0x140 >>>> [ 37.022458] smp_apic_timer_interrupt+0x3b/0x50 >>>> [ 37.023429] apic_timer_interrupt+0x8e/0xa0 >>>> [ 37.024303] RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x60 >>>> [ 37.025141] RSP: 0018:ffffc900004e3c10 EFLAGS: 00000246 ORIG_RAX: >>>> ffffffffffffff10 >>>> [ 37.026605] RAX: ffff88001448c180 RBX: ffffffff82727288 RCX: >>>> 0000000000000000 >>>> [ 37.028340] RDX: 0000000000000000 RSI: 0000000000000000 RDI: >>>> ffffffff82727288 >>>> [ 37.030077] RBP: ffffc900004e3c60 R08: 0000000000000000 R09: >>>> 0000000000000000 >>>> [ 37.031796] R10: 0000000000000000 R11: 0000000000000001 R12: >>>> 0000000000000000 >>>> [ 37.033546] R13: 0000000000000000 R14: 0000000000000000 R15: >>>> 00007f2689f93000 >>>> [ 37.035262] </IRQ> >>>> [ 37.035814] ? ftrace_likely_update+0x39/0x200 >>>> [ 37.036925] ? vm_normal_page+0xd7/0x1a0 >>>> [ 37.037886] unmap_page_range+0x775/0x14d0 >>>> [ 37.038658] unmap_single_vma+0x158/0x180 >>>> [ 37.039403] unmap_vmas+0x5b/0x80 >>>> [ 37.040202] exit_mmap+0x118/0x220 >>>> [ 37.040900] mmput+0xd5/0x240 >>>> [ 37.041479] do_exit+0xdb6/0x16d0 >>>> [ 37.042183] ? entry_SYSCALL_64_fastpath+0x5/0xbd >>>> [ 37.043365] do_group_exit+0x8a/0x160 >>>> [ 37.044282] SyS_exit_group+0x1d/0x20 >>>> [ 37.045192] entry_SYSCALL_64_fastpath+0x1f/0xbd >>>> [ 37.046321] RIP: 0033:0x7f268a676408 >>>> [ 37.047221] RSP: 002b:00007ffcba052ea8 EFLAGS: 00000246 ORIG_RAX: >>>> 00000000000000e7 >>>> [ 37.049042] RAX: ffffffffffffffda RBX: 000000000000007f RCX: >>>> 00007f268a676408 >>>> [ 37.050784] RDX: 000000000000007f RSI: 000000000000003c RDI: >>>> 000000000000007f >>>> [ 37.052512] RBP: 00007f268a96e688 R08: 00000000000000e7 R09: >>>> ffffffffffffffa0 >>>> [ 37.054281] R10: 0000000000000000 R11: 0000000000000246 R12: >>>> 00007f268a96ff40 >>>> [ 37.056004] R13: 0000000000000001 R14: 0000000000000000 R15: >>>> 00000000ffffffff >>>> [ 37.057765] Code: e8 56 14 48 ff eb ca e8 b5 42 4f ff 0f ff 0f 1f 00 >>>> eb a7 e8 a9 42 4f ff 0f ff 0f 1f 80 00 00 00 00 e9 48 ff ff ff e8 96 42 4f >>>> ff <0f> ff 0f 1f 40 00 e9 e5 fe ff ff 90 66 2e 0f 1f 84 00 00 00 00 >>>> [ 37.062621] ---[ end trace db04ba531557bbda ]--- >>>> >>>> >>>> To reproduce: >>>> >>>> git clone https://github.com/01org/lkp-tests.git >>>> cd lkp-tests >>>> bin/lkp qemu -k <bzImage> job-script # job-script is attached in >>>> this email >>>> >>>> >>>> >>>> Thanks, >>>> Xiaolong >>> >>> >>> >>> >>> -- >>> Kees Cook >>> Pixel Security > > > >-- >Kees Cook >Pixel Security
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