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Eric Dumazetdavem330
Eric Dumazet
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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+ imx6-dongle#14 /D975XBX > RIP: 0010:[<ffffffff815b54a4>] [<ffffffff815b54a4>] 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: > [<ffffffff815bcff4>] ? netif_rx+0x114/0x4c0 > [<ffffffff815b1831>] ? skb_copy_datagram_from_iovec+0x61/0x290 > [<ffffffff815b672a>] __skb_get_rxhash+0x1a/0xd0 > [<ffffffffa03b9538>] tun_get_user+0x418/0x810 [tun] > [<ffffffff8135f468>] ? delay_tsc+0x98/0xf0 > [<ffffffff8109605c>] ? __rcu_read_unlock+0x5c/0xa0 > [<ffffffffa03b9a41>] tun_chr_aio_write+0x81/0xb0 [tun] > [<ffffffff81145011>] ? __buffer_unlock_commit+0x41/0x50 > [<ffffffff811db917>] do_sync_write+0xa7/0xe0 > [<ffffffff811dc01f>] vfs_write+0xaf/0x190 > [<ffffffff811dc375>] sys_write+0x55/0xa0 > [<ffffffff81705540>] 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 [<ffffffff815b54a4>] skb_flow_dissect+0x314/0x3e0 > RSP <ffff88007d0d9c48> > ---[ 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 96442e4 (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 <[email protected]> Signed-off-by: Eric Dumazet <[email protected]> Cc: Jason Wang <[email protected]> Acked-by: Jason Wang <[email protected]> Signed-off-by: David S. Miller <[email protected]>
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drivers/net/tun.c

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -297,13 +297,12 @@ static void tun_flow_cleanup(unsigned long data)
297297
spin_unlock_bh(&tun->lock);
298298
}
299299

300-
static void tun_flow_update(struct tun_struct *tun, struct sk_buff *skb,
300+
static void tun_flow_update(struct tun_struct *tun, u32 rxhash,
301301
u16 queue_index)
302302
{
303303
struct hlist_head *head;
304304
struct tun_flow_entry *e;
305305
unsigned long delay = tun->ageing_time;
306-
u32 rxhash = skb_get_rxhash(skb);
307306

308307
if (!rxhash)
309308
return;
@@ -1010,6 +1009,7 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
10101009
int copylen;
10111010
bool zerocopy = false;
10121011
int err;
1012+
u32 rxhash;
10131013

10141014
if (!(tun->flags & TUN_NO_PI)) {
10151015
if ((len -= sizeof(pi)) > total_len)
@@ -1162,12 +1162,13 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
11621162
skb_shinfo(skb)->tx_flags |= SKBTX_DEV_ZEROCOPY;
11631163
}
11641164

1165+
rxhash = skb_get_rxhash(skb);
11651166
netif_rx_ni(skb);
11661167

11671168
tun->dev->stats.rx_packets++;
11681169
tun->dev->stats.rx_bytes += len;
11691170

1170-
tun_flow_update(tun, skb, tfile->queue_index);
1171+
tun_flow_update(tun, rxhash, tfile->queue_index);
11711172
return total_len;
11721173
}
11731174

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