From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: GPF in skb_flow_dissect Date: Thu, 13 Dec 2012 13:40:25 +0800 Message-ID: <50C96A49.2030404@redhat.com> References: <20121213041644.GB1611@redhat.com> <1355376177.12271.244.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Dave Jones , David Miller , netdev@vger.kernel.org To: Eric Dumazet Return-path: Received: from mx1.redhat.com ([209.132.183.28]:31818 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750829Ab2LMFkk (ORCPT ); Thu, 13 Dec 2012 00:40:40 -0500 In-Reply-To: <1355376177.12271.244.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On 12/13/2012 01:22 PM, Eric Dumazet wrote: > From: Eric Dumazet > > On Wed, 2012-12-12 at 23:16 -0500, Dave Jones wrote: >> Since todays net merge, I see this when I start openvpn.. >> >> general protection fault: 0000 [#1] PREEMPT SMP >> Modules linked in: ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 xt_conntrack nf_conntrack ip6table_filter ip6_tables xfs iTCO_wdt iTCO_vendor_support snd_emu10k1 snd_util_mem snd_ac97_codec coretemp ac97_bus microcode snd_hwdep snd_seq pcspkr snd_pcm snd_page_alloc snd_timer lpc_ich i2c_i801 snd_rawmidi mfd_core snd_seq_device snd e1000e soundcore emu10k1_gp gameport i82975x_edac edac_core vhost_net tun macvtap macvlan kvm_intel kvm binfmt_misc nfsd auth_rpcgss nfs_acl lockd sunrpc btrfs libcrc32c zlib_deflate firewire_ohci sata_sil firewire_core crc_itu_t radeon i2c_algo_bit drm_kms_helper ttm drm i2c_core floppy >> CPU 0 >> Pid: 1381, comm: openvpn Not tainted 3.7.0+ #14 /D975XBX >> RIP: 0010:[] [] skb_flow_dissect+0x314/0x3e0 >> RSP: 0018:ffff88007d0d9c48 EFLAGS: 00010206 >> RAX: 000000000000055d RBX: 6b6b6b6b6b6b6b4b RCX: 1471030a0180040a >> RDX: 0000000000000005 RSI: 00000000ffffffe0 RDI: ffff8800ba83fa80 >> RBP: ffff88007d0d9cb8 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000101 R12: ffff8800ba83fa80 >> R13: 0000000000000008 R14: ffff88007d0d9cc8 R15: ffff8800ba83fa80 >> FS: 00007f6637104800(0000) GS:ffff8800bf600000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 00007f563f5b01c4 CR3: 000000007d140000 CR4: 00000000000007f0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 >> Process openvpn (pid: 1381, threadinfo ffff88007d0d8000, task ffff8800a540cd60) >> Stack: >> ffff8800ba83fa80 0000000000000296 0000000000000000 0000000000000000 >> ffff88007d0d9cc8 ffffffff815bcff4 ffff88007d0d9ce8 ffffffff815b1831 >> ffff88007d0d9ca8 00000000703f6364 ffff8800ba83fa80 0000000000000000 >> Call Trace: >> [] ? netif_rx+0x114/0x4c0 >> [] ? skb_copy_datagram_from_iovec+0x61/0x290 >> [] __skb_get_rxhash+0x1a/0xd0 >> [] tun_get_user+0x418/0x810 [tun] >> [] ? delay_tsc+0x98/0xf0 >> [] ? __rcu_read_unlock+0x5c/0xa0 >> [] tun_chr_aio_write+0x81/0xb0 [tun] >> [] ? __buffer_unlock_commit+0x41/0x50 >> [] do_sync_write+0xa7/0xe0 >> [] vfs_write+0xaf/0x190 >> [] sys_write+0x55/0xa0 >> [] tracesys+0xdd/0xe2 >> Code: 41 8b 44 24 68 41 2b 44 24 6c 01 de 29 f0 83 f8 03 0f 8e a0 00 00 00 48 63 de 49 03 9c 24 e0 00 00 00 48 85 db 0f 84 72 fe ff ff <8b> 03 41 89 46 08 b8 01 00 00 00 e9 43 fd ff ff 0f 1f 40 00 48 >> RIP [] skb_flow_dissect+0x314/0x3e0 >> RSP >> ---[ end trace 6d42c834c72c002e ]--- >> >> >> Faulting instruction is >> >> 0: 8b 03 mov (%rbx),%eax >> >> rbx is slab poison (-20) so this looks like a use-after-free here... >> >> flow->ports = *ports; >> 314: 8b 03 mov (%rbx),%eax >> 316: 41 89 46 08 mov %eax,0x8(%r14) >> >> in the inlined skb_header_pointer in skb_flow_dissect >> >> Dave >> > Yes, commit 7694a3acc55a7 added this bug > > Its illegal to use skb after call to netif_rx_ni(skb); > > I would try following patch. > > Thanks ! > > [PATCH] tuntap: dont use skb after netif_rx_ni(skb) > > commit 96442e4242 (tuntap: choose the txq based on rxq) added > a use after free. > > Cache rxhash in a temp variable before calling netif_rx_ni() > > Reported-by: Dave Jones > Signed-off-by: Eric Dumazet > Cc: Jason Wang > --- > drivers/net/tun.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) Acked-by: Jason Wang > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > index 2ac2164..40b426e 100644 > --- a/drivers/net/tun.c > +++ b/drivers/net/tun.c > @@ -297,13 +297,12 @@ static void tun_flow_cleanup(unsigned long data) > spin_unlock_bh(&tun->lock); > } > > -static void tun_flow_update(struct tun_struct *tun, struct sk_buff *skb, > +static void tun_flow_update(struct tun_struct *tun, u32 rxhash, > u16 queue_index) > { > struct hlist_head *head; > struct tun_flow_entry *e; > unsigned long delay = tun->ageing_time; > - u32 rxhash = skb_get_rxhash(skb); > > if (!rxhash) > return; > @@ -1010,6 +1009,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, > int copylen; > bool zerocopy = false; > int err; > + u32 rxhash; > > if (!(tun->flags & TUN_NO_PI)) { > if ((len -= sizeof(pi)) > total_len) > @@ -1162,12 +1162,13 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, > skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY; > } > > + rxhash = skb_get_rxhash(skb); > netif_rx_ni(skb); > > tun->dev->stats.rx_packets++; > tun->dev->stats.rx_bytes += len; > > - tun_flow_update(tun, skb, tfile->queue_index); > + tun_flow_update(tun, rxhash, tfile->queue_index); > return total_len; > } > > >