From: Eric Dumazet <edumazet@xxxxxxxxxx>
On Wed, 2013-04-24 at 08:50 +0200, Mike Galbraith wrote:
> Giving 3.6-rt some routine usage runtime, while updating kernel git
> repositories, the below fell out, but didn't repeat while updating other
> repositories.
>
> [ 381.481464] ------------[ cut here ]------------
> [ 381.486090] WARNING: at include/linux/skbuff.h:536 inet_sk_rx_dst_set+0x8c/0xe0()
> [ 381.493566] Hardware name: MS-7502
> [ 381.493612] Modules linked in: ip6table_filter ip6_tables iptable_filter ip_tables ebtable_nat ebtables x_tables nfsd snd_pcm_oss snd_mixer_oss snd_seq nfs_acl snd_seq_device auth_rpcgss edd nfs fscache lockd sunrpc bridge ipv6 stp cpufreq_conservative cpufreq_ondemand cpufreq_userspace cpufreq_powersave acpi_cpufreq mperf nls_iso8859_1 nls_cp437 vfat fat fuse ext3 jbd arc4 rt2800usb rt2800lib crc_ccitt rt2x00usb rt2x00lib mac80211 iTCO_wdt iTCO_vendor_support cfg80211 hid_generic rfkill usb_storage snd_hda_codec_realtek sr_mod cdrom sg snd_hda_intel snd_hda_codec snd_hwdep snd_pcm snd_timer e1000e snd firewire_ohci firewire_core coretemp microcode soundcore lpc_ich mfd_core crc_itu_t snd_page_alloc i2c_i801 button ext4 mbcache jbd2 crc16 usbhid hid sd_mod crc_t10dif uhci_hcd ehci_hcd rtc_cmos ahci libahci libata thermal fan scsi_mod usbcore usb_common processor
> [ 381.493620] Pid: 6170, comm: git Not tainted 3.6.11.1-rt32-smp #52
> [ 381.493621] Call Trace:
> [ 381.493626] [<ffffffff8103cddf>] warn_slowpath_common+0x7f/0xc0
> [ 381.493629] [<ffffffff8103ce3a>] warn_slowpath_null+0x1a/0x20
> [ 381.493631] [<ffffffff813f6f0c>] inet_sk_rx_dst_set+0x8c/0xe0
> [ 381.493633] [<ffffffff813ece77>] tcp_rcv_established+0x797/0x7d0
> [ 381.493636] [<ffffffff813f82d4>] tcp_v4_do_rcv+0x134/0x220
> [ 381.493638] [<ffffffff813debc7>] tcp_prequeue_process+0x67/0xb0
> [ 381.493641] [<ffffffff813e373a>] tcp_recvmsg+0xaca/0xd70
> [ 381.493645] [<ffffffff810a627b>] ? __lock_release+0x6b/0xe0
> [ 381.493648] [<ffffffff8140f381>] inet_recvmsg+0x121/0x240
> [ 381.493651] [<ffffffff8140ead0>] ? inet_sock_destruct+0x230/0x230
> [ 381.493655] [<ffffffff8136fd49>] sock_aio_read.part.19+0xf9/0x120
> [ 381.493657] [<ffffffff8136fee0>] ? sock_aio_write+0x90/0xb0
> [ 381.493660] [<ffffffff8136fd96>] sock_aio_read+0x26/0x30
> [ 381.493662] [<ffffffff8116c503>] do_sync_read+0xa3/0xe0
> [ 381.493665] [<ffffffff8116ce9d>] vfs_read+0x14d/0x160
> [ 381.493667] [<ffffffff8116cefd>] sys_read+0x4d/0x90
> [ 381.493670] [<ffffffff81481812>] system_call_fastpath+0x16/0x1b
> [ 381.493671] ---[ end trace 0000000000000002 ]---
>
> 529 static inline struct dst_entry *skb_dst(const struct sk_buff *skb)
> 530 {
> 531 /* If refdst was not refcounted, check we still are in a
> 532 * rcu_read_lock section
> 533 */
> 534 WARN_ON((skb->_skb_refdst & SKB_DST_NOREF) &&
> 535 !rcu_read_lock_held() &&
> 536 !rcu_read_lock_bh_held());
> 537 return (struct dst_entry *)(skb->_skb_refdst & SKB_DST_PTRMASK);
> 538 }
>
Thanks for the report, here is a fix.
It will be a bit of a hassle to merge this one on net-next, as
tcp_prequeue() was moved in commit
b2fb4f54ecd47c42413d54b4666b06cf93c05abf
(tcp: uninline tcp_prequeue() )
David, maybe you prefer to pull into net tree the move, then I respin
the fix ?
[PATCH] tcp: force a dst refcount when prequeue packet
Before escaping RCU protected section and adding packet into
prequeue, make sure the dst is refcounted.
Reported-by: Mike Galbraith <bitbucket@xxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
---
include/net/tcp.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index cf0694d..a345480 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1049,6 +1049,7 @@ static inline bool tcp_prequeue(struct sock *sk, struct sk_buff *skb)
skb_queue_len(&tp->ucopy.prequeue) == 0)
return false;
+ skb_dst_force(skb);
__skb_queue_tail(&tp->ucopy.prequeue, skb);
tp->ucopy.memory += skb->truesize;
if (tp->ucopy.memory > sk->sk_rcvbuf) {
--
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