From 499744209b2cbca66c42119226e5470da3bb7040 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 12 Dec 2012 19:22:57 +0000 Subject: [PATCH] tuntap: dont use skb after netif_rx_ni(skb) 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 > 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 Acked-by: Jason Wang Signed-off-by: David S. Miller --- drivers/net/tun.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 2ac2164a1e39..40b426edc9e6 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; } -- 2.20.1