target/linux/generic/patches-3.18/081-04-ppp-don-t-override-sk-sk_state-in-pppoe_flush_dev.patch

   1 From: Guillaume Nault <g.nault@alphalink.fr>
   2 Date: Wed, 30 Sep 2015 11:45:33 +0200
   3 Subject: [PATCH] ppp: don't override sk->sk_state in pppoe_flush_dev()
   4
   5 Since commit 2b018d57ff18 ("pppoe: drop PPPOX_ZOMBIEs in pppoe_release"),
   6 pppoe_release() calls dev_put(po->pppoe_dev) if sk is in the
   7 PPPOX_ZOMBIE state. But pppoe_flush_dev() can set sk->sk_state to
   8 PPPOX_ZOMBIE _and_ reset po->pppoe_dev to NULL. This leads to the
   9 following oops:
  10
  11 [  570.140800] BUG: unable to handle kernel NULL pointer dereference at 00000000000004e0
  12 [  570.142931] IP: [<ffffffffa018c701>] pppoe_release+0x50/0x101 [pppoe]
  13 [  570.144601] PGD 3d119067 PUD 3dbc1067 PMD 0
  14 [  570.144601] Oops: 0000 [#1] SMP
  15 [  570.144601] Modules linked in: l2tp_ppp l2tp_netlink l2tp_core ip6_udp_tunnel udp_tunnel pppoe pppox ppp_generic slhc loop crc32c_intel ghash_clmulni_intel jitterentropy_rng sha256_generic hmac drbg ansi_cprng aesni_intel aes_x86_64 ablk_helper cryptd lrw gf128mul glue_helper acpi_cpufreq evdev serio_raw processor button ext4 crc16 mbcache jbd2 virtio_net virtio_blk virtio_pci virtio_ring virtio
  16 [  570.144601] CPU: 1 PID: 15738 Comm: ppp-apitest Not tainted 4.2.0 #1
  17 [  570.144601] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014
  18 [  570.144601] task: ffff88003d30d600 ti: ffff880036b60000 task.ti: ffff880036b60000
  19 [  570.144601] RIP: 0010:[<ffffffffa018c701>]  [<ffffffffa018c701>] pppoe_release+0x50/0x101 [pppoe]
  20 [  570.144601] RSP: 0018:ffff880036b63e08  EFLAGS: 00010202
  21 [  570.144601] RAX: 0000000000000000 RBX: ffff880034340000 RCX: 0000000000000206
  22 [  570.144601] RDX: 0000000000000006 RSI: ffff88003d30dd20 RDI: ffff88003d30dd20
  23 [  570.144601] RBP: ffff880036b63e28 R08: 0000000000000001 R09: 0000000000000000
  24 [  570.144601] R10: 00007ffee9b50420 R11: ffff880034340078 R12: ffff8800387ec780
  25 [  570.144601] R13: ffff8800387ec7b0 R14: ffff88003e222aa0 R15: ffff8800387ec7b0
  26 [  570.144601] FS:  00007f5672f48700(0000) GS:ffff88003fc80000(0000) knlGS:0000000000000000
  27 [  570.144601] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  28 [  570.144601] CR2: 00000000000004e0 CR3: 0000000037f7e000 CR4: 00000000000406a0
  29 [  570.144601] Stack:
  30 [  570.144601]  ffffffffa018f240 ffff8800387ec780 ffffffffa018f240 ffff8800387ec7b0
  31 [  570.144601]  ffff880036b63e48 ffffffff812caabe ffff880039e4e000 0000000000000008
  32 [  570.144601]  ffff880036b63e58 ffffffff812cabad ffff880036b63ea8 ffffffff811347f5
  33 [  570.144601] Call Trace:
  34 [  570.144601]  [<ffffffff812caabe>] sock_release+0x1a/0x75
  35 [  570.144601]  [<ffffffff812cabad>] sock_close+0xd/0x11
  36 [  570.144601]  [<ffffffff811347f5>] __fput+0xff/0x1a5
  37 [  570.144601]  [<ffffffff811348cb>] ____fput+0x9/0xb
  38 [  570.144601]  [<ffffffff81056682>] task_work_run+0x66/0x90
  39 [  570.144601]  [<ffffffff8100189e>] prepare_exit_to_usermode+0x8c/0xa7
  40 [  570.144601]  [<ffffffff81001a26>] syscall_return_slowpath+0x16d/0x19b
  41 [  570.144601]  [<ffffffff813babb1>] int_ret_from_sys_call+0x25/0x9f
  42 [  570.144601] Code: 48 8b 83 c8 01 00 00 a8 01 74 12 48 89 df e8 8b 27 14 e1 b8 f7 ff ff ff e9 b7 00 00 00 8a 43 12 a8 0b 74 1c 48 8b 83 a8 04 00 00 <48> 8b 80 e0 04 00 00 65 ff 08 48 c7 83 a8 04 00 00 00 00 00 00
  43 [  570.144601] RIP  [<ffffffffa018c701>] pppoe_release+0x50/0x101 [pppoe]
  44 [  570.144601]  RSP <ffff880036b63e08>
  45 [  570.144601] CR2: 00000000000004e0
  46 [  570.200518] ---[ end trace 46956baf17349563 ]---
  47
  48 pppoe_flush_dev() has no reason to override sk->sk_state with
  49 PPPOX_ZOMBIE. pppox_unbind_sock() already sets sk->sk_state to
  50 PPPOX_DEAD, which is the correct state given that sk is unbound and
  51 po->pppoe_dev is NULL.
  52
  53 Fixes: 2b018d57ff18 ("pppoe: drop PPPOX_ZOMBIEs in pppoe_release")
  54 Tested-by: Oleksii Berezhniak <core@irc.lg.ua>
  55 Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
  56 Signed-off-by: David S. Miller <davem@davemloft.net>
  57 ---
  58
  59 --- a/drivers/net/ppp/pppoe.c
  60 +++ b/drivers/net/ppp/pppoe.c
  61 @@ -313,7 +313,6 @@ static void pppoe_flush_dev(struct net_d
  62                         if (po->pppoe_dev == dev &&
  63                             sk->sk_state & (PPPOX_CONNECTED | PPPOX_BOUND | PPPOX_ZOMBIE)) {
  64                                 pppox_unbind_sock(sk);
  65 -                               sk->sk_state = PPPOX_ZOMBIE;
  66                                 sk->sk_state_change(sk);
  67                                 po->pppoe_dev = NULL;
  68                                 dev_put(dev);