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Date: Fri, 02 Oct 2015 11:01:45 +0300
From: Denys Fedoryshchenko <nuclearcat@...learcat.com>
To: Guillaume Nault <g.nault@...halink.fr>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
Paul Mackerras <paulus@...ba.org>,
Oleksii Berezhniak <core@....lg.ua>
Subject: Re: [PATCH net] ppp: don't override sk->sk_state in pppoe_flush_dev()
Here is similar panic after patch applied (it might be different bug),
got over netconsole:
[126348.610996] BUG: unable to handle kernel
NULL pointer dereference
at 0000000000000428
[126348.611656] IP:
[<ffffffffa00ea129>] pppoe_release+0x56/0x142 [pppoe]
[126348.612033] PGD 17d0b03067
PUD 17c721b067
PMD 0
[126348.612545] Oops: 0000 [#1]
SMP
[126348.612981] Modules linked in:
act_skbedit
sch_fq
cls_fw
act_police
cls_u32
sch_ingress
sch_sfq
sch_htb
pppoe
pppox
ppp_generic
slhc
netconsole
configfs
xt_nat
ts_bm
xt_string
xt_connmark
xt_TCPMSS
xt_tcpudp
xt_mark
iptable_filter
iptable_nat
nf_conntrack_ipv4
nf_defrag_ipv4
nf_nat_ipv4
nf_nat
nf_conntrack
iptable_mangle
ip_tables
x_tables
8021q
garp
mrp
stp
llc
bonding
[126348.617115] CPU: 0 PID: 5254 Comm: accel-pppd Not tainted
4.2.2-build-0087 #2
[126348.617632] Hardware name: Intel Corporation S2600GZ/S2600GZ, BIOS
SE5C600.86B.02.03.0003.041920141333 04/19/2014
[126348.618193] task: ffff8817cfbe0000 ti: ffff8817c6350000 task.ti:
ffff8817c6350000
[126348.618696] RIP: 0010:[<ffffffffa00ea129>]
[<ffffffffa00ea129>] pppoe_release+0x56/0x142 [pppoe]
[126348.619306] RSP: 0018:ffff8817c6353e28 EFLAGS: 00010202
[126348.619601] RAX: 0000000000000000 RBX: ffff8817a92b0400 RCX:
0000000000000000
[126348.620152] RDX: 0000000000000001 RSI: 00000000fffffe01 RDI:
ffffffff8180c18a
[126348.620715] RBP: ffff8817c6353e68 R08: 0000000000000000 R09:
0000000000000000
[126348.621254] R10: ffff88173c02b210 R11: 0000000000000293 R12:
ffff8817b3c18000
[126348.621784] R13: ffff8817b3c18030 R14: ffff8817967f1140 R15:
ffff8817d226c920
[126348.622330] FS: 00007f9444db9700(0000) GS:ffff8817dee00000(0000)
knlGS:0000000000000000
[126348.622876] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[126348.623202] CR2: 0000000000000428 CR3: 00000017c70b2000 CR4:
00000000001406f0
[126348.623760] Stack:
[126348.624056] 0000000100200018
0000000000000000
0000000100000000
ffff8817b3c18000
[126348.624925] ffffffffa00ec280
ffff8817b3c18030
ffff8817967f1140
ffff8817d226c920
[126348.625736] ffff8817c6353e88
ffffffff8180820a
ffff88173c02b200
0000000000000008
[126348.626533] Call Trace:
[126348.626873] [<ffffffff8180820a>] sock_release+0x1a/0x70
[126348.627183] [<ffffffff8180826d>] sock_close+0xd/0x11
[126348.627512] [<ffffffff81152c61>] __fput+0xdf/0x193
[126348.627845] [<ffffffff81152d43>] ____fput+0x9/0xb
[126348.628169] [<ffffffff810d098e>] task_work_run+0x78/0x8f
[126348.628517] [<ffffffff810038a9>] do_notify_resume+0x40/0x4e
[126348.628837] [<ffffffff818a5a0a>] int_signal+0x12/0x17
[126348.629131] Code:
48
8b
83
e0
00
00
00
a8
01
74
12
48
89
df
e8
0d
24
72
e1
b8
f7
ff
ff
ff
e9
eb
00
00
00
8a
43
12
a8
0b
74
1c
48
8b
83
a0
02
00
00
8b
80
28
04
00
00
65
ff
08
48
c7
83
a0
02
00
00
00
00
00
00
[126348.635060] RIP
[<ffffffffa00ea129>] pppoe_release+0x56/0x142 [pppoe]
[126348.635432] RSP <ffff8817c6353e28>
[126348.635718] CR2: 0000000000000428
[126348.641165] ---[ end trace 911ff90a1416e3d1 ]---
[126348.653235] Kernel panic - not syncing: Fatal exception
[126348.653538] Kernel Offset: disabled
[126348.677177] Rebooting in 5 seconds..
On 2015-09-30 12:45, Guillaume Nault wrote:
> Since commit 2b018d57ff18 ("pppoe: drop PPPOX_ZOMBIEs in
> pppoe_release"),
> pppoe_release() calls dev_put(po->pppoe_dev) if sk is in the
> PPPOX_ZOMBIE state. But pppoe_flush_dev() can set sk->sk_state to
> PPPOX_ZOMBIE _and_ reset po->pppoe_dev to NULL. This leads to the
> following oops:
>
> [ 570.140800] BUG: unable to handle kernel NULL pointer dereference
> at 00000000000004e0
> [ 570.142931] IP: [<ffffffffa018c701>] pppoe_release+0x50/0x101
> [pppoe]
> [ 570.144601] PGD 3d119067 PUD 3dbc1067 PMD 0
> [ 570.144601] Oops: 0000 [#1] SMP
> [ 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
> [ 570.144601] CPU: 1 PID: 15738 Comm: ppp-apitest Not tainted 4.2.0 #1
> [ 570.144601] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS Debian-1.8.2-1 04/01/2014
> [ 570.144601] task: ffff88003d30d600 ti: ffff880036b60000 task.ti:
> ffff880036b60000
> [ 570.144601] RIP: 0010:[<ffffffffa018c701>] [<ffffffffa018c701>]
> pppoe_release+0x50/0x101 [pppoe]
> [ 570.144601] RSP: 0018:ffff880036b63e08 EFLAGS: 00010202
> [ 570.144601] RAX: 0000000000000000 RBX: ffff880034340000 RCX:
> 0000000000000206
> [ 570.144601] RDX: 0000000000000006 RSI: ffff88003d30dd20 RDI:
> ffff88003d30dd20
> [ 570.144601] RBP: ffff880036b63e28 R08: 0000000000000001 R09:
> 0000000000000000
> [ 570.144601] R10: 00007ffee9b50420 R11: ffff880034340078 R12:
> ffff8800387ec780
> [ 570.144601] R13: ffff8800387ec7b0 R14: ffff88003e222aa0 R15:
> ffff8800387ec7b0
> [ 570.144601] FS: 00007f5672f48700(0000) GS:ffff88003fc80000(0000)
> knlGS:0000000000000000
> [ 570.144601] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 570.144601] CR2: 00000000000004e0 CR3: 0000000037f7e000 CR4:
> 00000000000406a0
> [ 570.144601] Stack:
> [ 570.144601] ffffffffa018f240 ffff8800387ec780 ffffffffa018f240
> ffff8800387ec7b0
> [ 570.144601] ffff880036b63e48 ffffffff812caabe ffff880039e4e000
> 0000000000000008
> [ 570.144601] ffff880036b63e58 ffffffff812cabad ffff880036b63ea8
> ffffffff811347f5
> [ 570.144601] Call Trace:
> [ 570.144601] [<ffffffff812caabe>] sock_release+0x1a/0x75
> [ 570.144601] [<ffffffff812cabad>] sock_close+0xd/0x11
> [ 570.144601] [<ffffffff811347f5>] __fput+0xff/0x1a5
> [ 570.144601] [<ffffffff811348cb>] ____fput+0x9/0xb
> [ 570.144601] [<ffffffff81056682>] task_work_run+0x66/0x90
> [ 570.144601] [<ffffffff8100189e>] prepare_exit_to_usermode+0x8c/0xa7
> [ 570.144601] [<ffffffff81001a26>]
> syscall_return_slowpath+0x16d/0x19b
> [ 570.144601] [<ffffffff813babb1>] int_ret_from_sys_call+0x25/0x9f
> [ 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
> [ 570.144601] RIP [<ffffffffa018c701>] pppoe_release+0x50/0x101
> [pppoe]
> [ 570.144601] RSP <ffff880036b63e08>
> [ 570.144601] CR2: 00000000000004e0
> [ 570.200518] ---[ end trace 46956baf17349563 ]---
>
> pppoe_flush_dev() has no reason to override sk->sk_state with
> PPPOX_ZOMBIE. pppox_unbind_sock() already sets sk->sk_state to
> PPPOX_DEAD, which is the correct state given that sk is unbound and
> po->pppoe_dev is NULL.
>
> Fixes: 2b018d57ff18 ("pppoe: drop PPPOX_ZOMBIEs in pppoe_release")
> Tested-by: Oleksii Berezhniak <core@....lg.ua>
> Signed-off-by: Guillaume Nault <g.nault@...halink.fr>
> ---
> drivers/net/ppp/pppoe.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
> index 3837ae3..2ed7506 100644
> --- a/drivers/net/ppp/pppoe.c
> +++ b/drivers/net/ppp/pppoe.c
> @@ -313,7 +313,6 @@ static void pppoe_flush_dev(struct net_device *dev)
> if (po->pppoe_dev == dev &&
> sk->sk_state & (PPPOX_CONNECTED | PPPOX_BOUND | PPPOX_ZOMBIE))
> {
> pppox_unbind_sock(sk);
> - sk->sk_state = PPPOX_ZOMBIE;
> sk->sk_state_change(sk);
> po->pppoe_dev = NULL;
> dev_put(dev);
--
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