Message-Id: <FD63B116-C1D0-4008-B10A-FC118B69124C@holtmann.org>
Date:   Tue, 23 May 2017 11:06:23 -0700
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Lin Zhang <xiaolou4617@...il.com>
Cc:     aar@...gutronix.de, Stefan Schmidt <stefan@....samsung.com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-wpan@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v2 2/2] net: ieee802154: fix net_device reference
 release too early

Hi Lin,

> This patch fixes the kernel oops when release net_device reference in
> advance. In function raw_sendmsg(i think the dgram_sendmsg has the same
> problem), there is a race condition between dev_put and dev_queue_xmit
> when the device is gong that maybe lead to dev_queue_ximt to see
> an illegal net_device pointer.
> 
> My test kernel is 3.13.0-32 and because i am not have a real 802154 
> device, so i change lowpan_newlink function to this:
> 
>        /* find and hold real wpan device */
>        real_dev = dev_get_by_index(src_net, nla_get_u32(tb[IFLA_LINK]));
>        if (!real_dev)
>                return -ENODEV;
> //      if (real_dev->type != ARPHRD_IEEE802154) {
> //              dev_put(real_dev);
> //              return -EINVAL;
> //      }
>        lowpan_dev_info(dev)->real_dev = real_dev;
>        lowpan_dev_info(dev)->fragment_tag = 0;
>        mutex_init(&lowpan_dev_info(dev)->dev_list_mtx);
> 
> Also, in order to simulate preempt, i change the raw_sendmsg function 
> to this:
> 
>        skb->dev = dev;
>        skb->sk  = sk;
>        skb->protocol = htons(ETH_P_IEEE802154);
>        dev_put(dev);
>        //simulate preempt
>        schedule_timeout_uninterruptible(30 * HZ);
>        err = dev_queue_xmit(skb);
>        if (err > 0)
>                err = net_xmit_errno(err);
> 
> and this is my userspace test code named test_send_data:
> 
> int main(int argc, char **argv)
> {
>        char buf[127];
>        int sockfd;
>        sockfd = socket(AF_IEEE802154, SOCK_RAW, 0);
>        if (sockfd < 0) {
>                printf("create sockfd error: %s\n", strerror(errno));
>                return -1;
>        }
>        send(sockfd, buf, sizeof(buf), 0);
>        return 0;
> }
> 
> 
> This is my test case:
> 
> root@...nglin-x-computer:~/develop/802154# uname -a
> Linux zhanglin-x-computer 3.13.0-32-generic #57-Ubuntu SMP Tue Jul 15
> 03:51:08 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
> root@...nglin-x-computer:~/develop/802154# ip link add link eth0 name
> lowpan0 type lowpan
> root@...nglin-x-computer:~/develop/802154#
> //keep the lowpan0 device down
> root@...nglin-x-computer:~/develop/802154# ./test_send_data &
> //wait a while
> root@...nglin-x-computer:~/develop/802154# ip link del link dev lowpan0
> //the device is gone
> //oops
> [381.303307] general protection fault: 0000 [#1]SMP
> [381.303407] Modules linked in: af_802154 6lowpan bnep rfcomm
> bluetooth nls_iso8859_1 snd_hda_codec_hdmi snd_hda_codec_realtek
> rts5139(C) snd_hda_intel
> snd_had_codec snd_hwdep snd_pcm snd_page_alloc snd_seq_midi
> snd_seq_midi_event snd_rawmidi snd_req intel_rapl snd_seq_device
> coretemp i915 kvm_intel
> kvm snd_timer snd crct10dif_pclmul crc32_pclmul ghash_clmulni_intel
> cypted drm_kms_helper drm i2c_algo_bit soundcore video mac_hid
> parport_pc ppdev ip parport hid_generic
> usbhid hid ahci r8169 mii libahdi
> [381.304286] CPU:1 PID: 2524 Commm: 1 Tainted: G C 0 3.13.0-32-generic
> [381.304409] Hardware name: Haier Haier DT Computer/Haier DT Codputer,
> BIOS FIBT19H02_X64 06/09/2014
> [381.304546] tasks: ffff000096965fc0 ti: ffffB0013779c000 task.ti:
> ffffB8013779c000
> [381.304659] RIP: 0010:[<ffffffff01621fe1>] [<ffffffff81621fe1>]
> __dev_queue_ximt+0x61/0x500
> [381.304798] RSP: 0018:ffffB8013779dca0 EFLAGS: 00010202
> [381.304880] RAX: 272b031d57565351 RBX: 0000000000000000 RCX: ffff8800968f1a00
> [381.304987] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8800968f1a00
> [381.305095] RBP: ffff8e013773dce0 R08: 0000000000000266 R09: 0000000000000004
> [381.305202] R10: 0000000000000004 R11: 0000000000000005 R12: ffff88013902e000
> [381.305310] R13: 000000000000007f R14: 000000000000007f R15: ffff8800968f1a00
> [381.305418] FS:  00007fc57f50f740(0000) GS: ffff88013fc80000(0000)
> knlGS: 0000000000000000
> [381.305540] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [381.305627] CR2: 00007fad0841c000 CR3: 00000001368dd000 CR4: 00000000001007e0
> [361.905734] Stack:
> [381.305768]  00000000002052d0 000000003facb30a ffff88013779dcc0
> ffff880137764000
> [381.305898]  ffff88013779de70 000000000000007f 000000000000007f
> ffff88013902e000
> [381.306026]  ffff88013779dcf0 ffffffff81622490 ffff88013779dd39
> ffffffffa03af9f1
> [381.306155] Call Trace:
> [381.306202]  [<ffffffff81622490>] dev_queue_xmit+0x10/0x20
> [381.306294]  [<ffffffffa03af9f1>] raw_sendmsg+0x1b1/0x270 [af_802154]
> [381.306396]  [<ffffffffa03af054>] ieee802154_sock_sendmsg+0x14/0x20 [af_802154]
> [381.306512]  [<ffffffff816079eb>] sock_sendmsg+0x8b/0xc0
> [381.306600]  [<ffffffff811d52a5>] ? __d_alloc+0x25/0x180
> [381.306687]  [<ffffffff811a1f56>] ? kmem_cache_alloc_trace+0x1c6/0x1f0
> [381.306791]  [<ffffffff81607b91>] SYSC_sendto+0x121/0x1c0
> [381.306878]  [<ffffffff8109ddf4>] ? vtime_account_user+x54/0x60
> [381.306975]  [<ffffffff81020d45>] ? syscall_trace_enter+0x145/0x250
> [381.307073]  [<ffffffff816086ae>] SyS_sendto+0xe/0x10
> [381.307156]  [<ffffffff8172c87f>] tracesys+0xe1/0xe6
> [381.307233] Code: c6 a1 a4 ff 41 8b 57 78 49 8b 47 20 85 d2 48 8b 80
> 78 07 00 00 75 21 49 8b 57 18 48 85 d2 74 18 48 85 c0 74 13 8b 92 ac
> 01 00 00 <3b> 50 10 73 08 8b 44 90 14 41 89 47 78 41 f6 84 24 d5 00 00
> 00
> [381.307801] RIP [<ffffffff81621fe1>] _dev_queue_xmit+0x61/0x500
> [381.307901]  RSP <ffff88013779dca0>
> [381.347512] Kernel panic - not syncing: Fatal exception in interrupt
> [381.347747] drm_kms_helper: panic occurred, switching back to text console
> 
> In my opinion, there is always exist a chance that the device is gong
> before call dev_queue_xmit.
> 
> I think the latest kernel is have the same problem and that 
> dev_put should be behind of the dev_queue_xmit.
> 
> Signed-off-by: Lin Zhang <xiaolou4617@...il.com>
> Acked-by: Stefan Schmidt <stefan@....samsung.com>
> ---
> changelog:
> 
> v1 -> v2:
>        * split v1 into two patches, per Stefan Schmidt.
> 
> Hello, Stefan:
> 	If you have a real 802154 device, maybe use the test case as above, thanks.
> 
> Thanks to Stefan Schmidt for reviewing !
> ---
> net/ieee802154/socket.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)

patch has been applied to bluetooth-next tree.

Regards

Marcel

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